GB2603596A

GB2603596A - Enhanced automated fibre placement method

Info

Publication number: GB2603596A
Application number: GB2117065.9A
Authority: GB
Inventors: Rezai Amir
Original assignee: BAE Systems PLC
Current assignee: BAE Systems PLC
Priority date: 2020-11-26
Filing date: 2021-11-26
Publication date: 2022-08-10
Anticipated expiration: 2041-11-26
Also published as: GB202117065D0; GB2603596B; GB202018581D0

Abstract

A method of layup for fibre-reinforced composite parts comprises: providing a set of tapes or tows S201, wherein the first tape or tow comprises a first set of reinforcement fibres 100, including a first reinforcement fibre 100A; forming a first discontinuity 110A of a first set of discontinuities in the first reinforcement fibre; and placing the set of tapes or tows. An apparatus and a composite part are also described. Providing the set of tapes or tows may include spooling. Forming the first discontinuity, which may be a partial reduction in cross-sectional area and/or diameter or parting of the fibre, may comprise laser ablating, electron beam cutting, cutting, shearing and/or punching or water jetting the first reinforcement fibre. Placing the set of tapes or tows may comprise steering the first tape or tow in a first arc of a set of arcs. A second discontinuity 110B may be formed of the first set of discontinuities in the first reinforcement fibre, wherein the first discontinuity and second discontinuities may be mutually spaced apart axially. The method provides increased steerability, allowing for tighter radii, during layup of fibre-reinforced composite parts.

Description

ENHANCED AUTOMATED FIBRE PLACEMENT METHOD

FIELD OF THE INVENTION

The present invention relates to layup for fibre-reinforced composites, for 5 example using automated tape laying and/or automated fibre placement. More specifically, the present invention relates to the steering of tows in fibre-reinforced composite tapes.

BACKGROUND

io Automated layup for fibre-reinforced composites, for example by automated tape laying (ATL) and automated fibre placement (AFP), typically involves laying fibre tapes, fabrics or tows onto moulds, using robots or CNC machines, for example. The tapes, fabrics and tows may be binder infused or resin impregnated (also known as pre-pregs). Layup for fibre-reinforced composite parts may be accelerated by laying multiple courses concurrently, laying multiple tapes or tows simultaneously and/or by increasing the width of the tapes, fabrics or tows. ATL typically uses tapes (also known as fabrics or cloths) having relatively wider widths of 2, 3, 6, 12 or 24 inch (nominally 51, 76, 152, 305, or 610 mm) while AFP typically uses tows (also known as ribbons) having relatively narrower widths of 1/8, 1/4, 1/2 or 1 inch (3.17, 6.35, 12.7 or 25.4 mm), though there is the drive to further increase the width of tows to 1.5 inches (38.1 mm). The selection of widths of the tapes, fabrics or tows is typically limited by part curvature in two or three dimensions.

ATL is suitable where part curvature in two or three dimensions is relatively lower while AFP is suitable where part curvature in two or three dimensions is relatively higher. Particularly, the respective widths of the tapes, fabrics and tows limit achievable part curvature in two or three dimensions: defects such as wrinkles and/or buckling are induced if the radii of in-plane curvature are too high for the respective widths. Hence, by using the relatively narrower tows in -2 -AFP, relatively more complex parts having relatively higher curvatures in two or three dimensions may be achieved compared with using the relatively wider tapes or fabrics in ATL. Nevertheless, rates of layup using ATL are relatively higher than using AFP, since the tapes or fabrics are relatively wider than the tows.

However, the minimum radius of in-plane curvature for a 1/8 inch tow is 650 mm while the minimum radius of in-plane curvature for a 1/2 inch tow is 2600 mm, thereby limiting part curvature in two or three dimensions and hence part complexity.

Hence, there is a need to improve layup for fibre-reinforced composites, for example using automated tape laying and/or automated fibre placement.

SUMMARY OF THE INVENTION

It is one aim of the present invention, amongst others, to provide a method of layup for fibre-reinforced composite parts which at least partially obviates or mitigates at least some of the disadvantages of the prior art, whether identified herein or elsewhere. For instance, it is an aim of embodiments of the invention to provide a method of layup for fibre-reinforced composite parts that enables manufacture of parts having relatively higher curvatures in two or three dimensions compared with conventional methods. For instance, it is an aim of embodiments of the invention to provide an apparatus for layup for fibre-reinforced composites.

A first aspect provides a method of layup for fibre-reinforced composite parts, the method comprising: providing a set of tapes or tows, including a first tape or tow, wherein the first tape or tow comprises a first set of reinforcement fibres, including a first reinforcement fibre; -3 -forming a first discontinuity of a first set of discontinuities in the first reinforcement fibre of the first tape or tow; and placing the set of tapes or tows, including the first tape or tow having the first discontinuity of the first set of discontinuities formed in the first reinforcement fibre.

A second aspect provides an apparatus for layup for fibre-reinforced composite parts from, at least in part, a set of tapes or tows, including a first tape or tow, wherein the first tape or tow comprises a first set of reinforcement fibres, including a first reinforcement fibre, the apparatus comprising: io means for forming a first discontinuity of a first set of discontinuities in the first reinforcement fibre of the first tape or tow; and means for placing the first tape or tow having the first discontinuity of the first set of discontinuities in the first reinforcement fibre of the first tape or tow.

A third aspect provides a fibre-reinforced composite part, or a precursor thereof, manufactured, at least in part, according to the method of the first aspect, using the tape or tow according to the fourth aspect and/or using the apparatus according to the second aspect.

A fourth aspect provides a tape or tow, comprising a first set of reinforcement fibres, including a first reinforcement fibre; wherein the first reinforcement fibre comprises a first discontinuity of a first set of discontinuities therein.

A fifth aspect provides a method of manufacturing a fibre-reinforced composite part, the method comprising: laying up of the fibre-reinforced composite according to the first aspect or the fourth aspect; and providing a matrix, comprising a first polymeric composition, for the layup.

A sixth aspect provides a method of tape or tow steering in the lay-up of fibre-reinforced composite parts, the method comprising: -4 -providing a set of tapes or tows, including a first tape or tow, wherein the first tape or tow comprises a first set of reinforcement fibres, including a first reinforcement fibre; forming a first discontinuity of a first set of discontinuities in the first reinforcement fibre of the first tape or tow; and placing the set of tapes or tows, including the first tape or tow having the first discontinuity of the first set of discontinuities formed in the first reinforcement fibre.

A seventh aspect provides an apparatus for tape or tow steering in the layup of fibre-reinforced composite parts from, at least in part, a set of tapes or tows, including a first tape or tow, wherein the first tape or tow comprises a first set of reinforcement fibres, including a first reinforcement fibre, the apparatus comprising: means for forming a first discontinuity of a first set of discontinuities in the first reinforcement fibre of the first tape or tow: and means for placing the first tape or tow having the first discontinuity of the first set of discontinuities in the first reinforcement fibre of the first tape or tow.

DETAILED DESCRIPTION

According to the present invention there is provided a method, as set forth in the appended claims and in the above aspects. Also provided is an apparatus and a fibre-reinforced composite part. Other features of the invention will be apparent from the dependent claims, and the description that follows.

Method of Layup The first aspect provides a method of layup for fibre-reinforced composite parts, the method comprising: -5 -providing a set of tapes or tows, including a first tape or tow, wherein the first tape or tow comprises a first set of reinforcement fibres, including a first reinforcement fibre; forming a first discontinuity of a first set of discontinuities in the first reinforcement fibre of the first tape or tow; and placing the set of tapes or tows, including the first tape or tow having the first discontinuity of the first set of discontinuities formed in the first reinforcement fibre.

In this way, a mechanical property, for example a tensile strength and/or a ttp stiffness, of the first set of reinforcement fibres of the first tape or tow is attenuated due to the first discontinuity of the first set of discontinuities in the first reinforcement fibre. By attenuating the mechanical property in this way, the minimum radius of in-plane curvature is reduced compared with the intact first tape or tow (i.e. the first tape or tow without the first discontinuity formed in the first reinforcement fibre thereof), thereby enabling manufacture of pads having relatively higher curvatures in two or three dimensions compared with using the intact first tape or tow. In other words, steerability of the first tape or tow is enhanced because the discontinuities allow for tighter radii with discontinuities proximal the inner radius of the tape or tow relieving compression therein and/or discontinuities proximal the outer radius of the tape or tow relieving tension therein. For example, the first discontinuity may be formed in the first reinforcement fibre at a first predetermined position so as to provide the enhanced steerability where required, such as according to the local curvature in two or three dimensions. Particularly, the first discontinuity increases path mobility of the first reinforcement fibre, thereby reducing formation of defects such as wrinkles and/or buckling. While the first discontinuity in the first reinforcement fibre may locally reduce strength and/or stiffness of the first tape or tow, the method according to the first aspect results in gains in steerability of the first tape or tow and/or manufacturing efficiency that more than offset any such local reductions in strength and/or stiffness. Additionally and/or -6 - alternatively, a local reduction in strength and/or stiffness of the first tape or tow due to the first discontinuity in the first reinforcement fibre may advantageously provide graded properties such as for aeroelastic tailoring, thereby providing enhanced flexibility of and/or improved local damping in the manufactured fibre-reinforced composite, compared with the intact first tape or tow, by controlling structural properties of the fibres.

In other words, the first aspect provides a method of layup for fibre-reinforced composite parts, the method comprising: providing a tape or tow (i.e. the first tape or tow) comprising reinforcement to fibres (i.e. the set of reinforcement fibres); forming a predetermined distribution of perforations (i.e. discontinuities) in the reinforcement fibres of the tape or tow; and placing the perforated tape or tow, for example by ATL or AFP.

In one example, the method comprises and/or is a method of steering the perforated tape. In one example, the method comprises and/or is a method of grading properties of the fibre-reinforced composite parts.

In one example, the method is a method of increasing steerability (e.g. in-plane steerability) during layup of fibre-reinforced composite parts, for example compared with conventional layup. In one example, the method is a method of controlling structural properties during layup of fibre-reinforced composite parts, for example compared with conventional layup. In one example, the method is a method of introducing selective fibre breaks.

The method is of layup for fibre-reinforced composite parts.

The method comprises providing the set of tapes or tows (i.e. a narrow tape comprising reinforcement fibres), including the first tape or tow, wherein the first tape or tow comprises the first set of reinforcement fibres, including the first reinforcement fibre. -7 -

In one example, the first tape or tow has a width Win a range from 0.03125 inches (0.79 mm) to 12 inches (304.8 mm), preferably in a range from 0.0625 inches (1.59 mm) to 6 inches (152.4 mm), more preferably in a range from 0.125 inches (3.175 mm) to 1 inch (25.4 mm).

ATL typically uses tapes (also known as fabrics or cloths) having relatively wider widths of 2, 3,6, 12 or 24 inch (nominally 51, 76, 152, 305, or 610 mm) while AFP typically uses tows (also known as ribbons) having relatively narrower widths of 1/8, 1/4, 1/2 or 1 inch (3.17, 6.35, 12.7 or 25.4 mm), though there is the drive to further increase the width of tows to 1.5 inches (38.1 mm).

io In one example, the first tape comprises and/or is a uniaxial tape, a multiaxial tape, a woven tape or a braided tape such as a flat braid, a biaxial braid, a triaxial braid, an elasticated braid or a tubular braid, for example having a weight in a range from 60 g/m2-1200 g/m2. Other tapes are known.

In one example, the first tow comprises and/or is a 1K tow, a 3K tow, a 6K 15 tow, a 12 K tow, a 24K tow or a 50K tow, for example having a weight in a range from 60 g/m2 -1200 g/m2. Other tows are known.

In one example, providing the set of tapes or tows comprises spooling the first tape or tow from a first spool. Spooling in ATL and AFP is known.

In one example, providing the set of tapes or tows comprises spreading the first tape or tow, before and/or after forming the first discontinuity.

Reinforcement Fibres In one example, the first set of reinforcement fibres comprises non-metal fibres for example glass fibres such as A-glass, E-glass, E-CR-glass, C-glass, D-glass, R-glass, S-glass, S-2-glass and HS-glass; carbon fibres such as aerospace or industrial grades of IM2A, IM2C, IM5, IM6, IM7, IM8, IM9, 1M1, AS4, AS4A, AS4C, AS4D, AS7, HMSO and HM63; aramid fibres such as Kevlar (RTM), Nomex (RTM) and Technora (RTM); Ultra-High Molecular Weight Polyethylene (UHMwPE) fibres such as Dyneema (RTM); basalt fibres such as Basfiber (RTM) or Wiking (RTM) Super B; and/or mixtures thereof. In one -8 -example, the first set of reinforcement fibres comprises metal and/or alloy fibres for example titanium, aluminium and/or copper and/or alloys thereof; stainless steel fibres; and/or mixtures thereof. In one example, the first set of reinforcement fibres comprises a mixture of non-metal and metal fibres.

In one example, the first reinforcement fibre has a diameter in a range from 2 pm to 100 pm, preferably in a range from 4 pm to 50 pm, more preferably in a range from 5 pm to 20 pm, most preferably in a range from 6 pm to 10 pm, for example 6,pm, 7 pm, 8 pm, 9 pm or 10 pm. Typically, suitable carbon fibres have a diameter in a range from 5 pm to 10 pm and suitable glass fibres have a io diameter in a range from 4 pm to 20 pm.

In one example, a volume fraction Vr J,tape Or tOW of the first set of reinforcement fibres is in a range from 50% to 100%, preferably in a range from 60% to 95%, for example 70%, 80% or 90%, by volume of the tape or tow. In this way, a relatively high volume fraction 10,tape or tow of the first set of is reinforcement fibres in the tape or tow may be provided.

In one example, a volume fraction 171,p continuous fibres, not having discontinuities therein) of the first set of reinforcement fibres is in a range from 1% to 99%, preferably in a range from 40% to 95%, more preferably in the range from 70% to 90%, for example 70%, 75%, 80%, 85% or 90%, by volume of the first set of reinforcement fibres. It should be understood that the volume fraction V1 pristine of pristine fibres is the volume fraction of continuous fibres of the first set of reinforcement fibres i.e. fibres not comprising discontinuities therein. In other words, the majority of the reinforcement fibres may be pristine, with only a minority of the reinforcement fibres including discontinuities so as to achieve a significant increase in steerability (i.e. introducing selective fibre breaks where local increased steerability is required). Preferably the discontinuities are introduced to the fibres (i.e. fibre breaks) on the fly. Generally, the discontinuities are provided in localised regions of the fibre-reinforced composite parts so as to locally provide the desired steerability. That is, the discontinuities may be heterogeneously ristine of pristine fibres (i.e. intact, -9 - (rather than homogeneously or uniformly) distributed through the fibre-reinforced composite parts, depending, at least in part, on the shapes in three dimensions of the fibre-reinforced composite parts. Particularly, the distribution of discontinuities may be topologically optimised. That is, a spacing, and/or density of the discontinuities may be locally optimised to achieve maximum steerability whilst minimising reductions in mechanical performance. It should be understood that a volume fraction Vf,pristine of, for example, 90%, and a volume fraction V1 of, for example, 60%, means that the volume fraction of pristine fibres in the fibre-reinforced composite parts is the product of these io volume fractions and hence 54%. In this way, the volume fraction V1 pristine of pristine fibres of the first set of reinforcement fibres in the filament may tend towards the limit for conventional filaments including reinforcement fibres while having a relatively high volume fraction Vt. of the first set of reinforcement fibres, thereby allowing parts having complex shapes in three dimensions to be fabricated due to the relatively lower volume fraction V, j /pristine of pristine fibres of the first set of reinforcement fibres, while the parts have improved mechanical properties due to the relatively higher volume fraction V1 tapeor tow of the first set of reinforcement fibres in the tape or tow. In this way, a balance between mechanical performance and steerability is provided.

In one example, a volume fraction 1/1 of the first set of reinforcement fibres is in a range from 30% to 90%, preferably in a range from 40% to 80%, more preferably in a range from 40% to 70%, for example 40%, 45%, 50%, 55%, 60%, 65% or 70% by volume of the fibre-reinforced composite parts. It should be understood that generally, the volume fraction Vm of the matrix, for example the first polymeric composition, is related to the volume fraction Vr of the reinforcement fibres, for example the first set of reinforcement fibres, by yr + VT, = 1. In this way, a relatively high volume fraction VI, of the first set of reinforcement fibres in the fibre-reinforced composite parts may be provided.

-10 -In one example, the first reinforcement fibre has a length L greater than or equal to a critical length 1, of the first reinforcement fibre in the filament, preferably wherein L > 31,, more preferably wherein L > 51,, most preferably wherein L > 71,. The minimum length is controlled to be above the critical length /e for the composite so that efficient load transfer into the fibre occurs. The critical length 1, of the first reinforcement fibre in the filament is directly proportional to a diameter of the first reinforcement fibre and a strength of the first reinforcement fibre and inversely proportional to an interfacial shear strength between the first reinforcement fibre and the first polymeric composition (i.e. the matrix).

io In one example, the first reinforcement fibre has a length of at least 2 mm, preferably at least 10 cm, more preferably at least 1 m, most preferably at least 10 m. It should be understood that the length of the first reinforcement fibre is a total length of the first reinforcement fibre i.e. including discontinuities therein. That is, the first reinforcement fibre comprises and/or is a continuous fibre. In contrast, chopped fibres typically have lengths less than 3 mm and tend to be arranged randomly or less than perfectly aligned. In one example, the first reinforcement fibre has a length corresponding with, for example equal to, a length of the tape or tow.

Second Reinforcement Fibre In one example, the first set of reinforcement fibres includes a second reinforcement fibre and the method comprises forming a first discontinuity of a second set of discontinuities in the second reinforcement fibre, wherein the first discontinuity of the first set of discontinuities and the first discontinuity of the second set of discontinuities are mutually spaced apart axially. That is, respective discontinuities in the first reinforcement fibre and in the second reinforcement fibre are axially offset. In this way, a stiffness of the first set of reinforcement fibres is attenuated, allowing laying of the first tape or tow in a relatively tight arc, reducing formation of defects such as wrinkles and/or buckling, enabling fabrication of relatively complex parts. In contrast, if the first discontinuity of the first set of discontinuities and the first discontinuity of the second set of discontinuities were axially aligned, while the strength and/or stiffness of the first set of reinforcement fibres is attenuated, the mechanical property of the part manufactured therefrom may be compromised due to the axial alignment of the respective discontinuities. The second reinforcement fibre may be as described with respect to the first reinforcement fibre.

Polymeric Composition In one example, the first set of reinforcement fibres, for example the first reinforcement fibre, is surrounded, at least in part, with the first polymeric composition, for example when the first tape or tow is a pre-preg. In this way, io handling of the first tape or tow is improved. In one example, the first tape or tow is a pre-impregnated tape or tow. In one example, the first reinforcement fibre is dry i.e. not surrounded, at least in part, with the first polymeric composition.

Generally, pre-preg is "pre-impregnated" reinforcement fibres where a thermoset polymer matrix material, such as an epoxy, or a thermoplastic resin matrix is already present. The fibres may take the form of a weave and the matrix is used to bond the fibres together and to other components during manufacture. The thermoset matrix is only partially cured to allow easy handling; this B-Stage material requires cold storage to prevent complete curing. B-Stage pre-preg is always stored in cooled areas since heat accelerates complete polymerization.

Thermoplastic matrices do not require such cold-storage. Hence, composite structures built of pre-pregs will mostly require an oven or autoclave to cure. Pre-preg allows impregnation of the fibres on a flat surface, for example, and then later, laying of the impregnated fibres to provide a desired shape which could be otherwise problematic to lay without the matrix.

Thermoplastic prepregs may be provided in unidirectional tape, or in fabrics that are woven or stitched, for example.

In one example, the first polymeric composition comprises a first thermoplastic, selected from a group comprising acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), polycarbonate (PC), polyamide (PA), polystyrene -12 - (PS), high-density polyethylene (HDPE), PC/ABS, polyethylene terephthalate (PETG), polyphenylsulfone (PPSU), high impact polystyrene (HIPS), polytetrafluoroethylene (PTFE), lignin, rubber, and/or a polyaryletherketone (PAEK), such as polyetherketoneketone (PEKK), polyetheretherketone (PEEK) and polyetherimide (PEI). In one example, the first thermoplastic comprises, consists of and/or is PEKK, PEEK and/or PEI, preferably PEKK and/or PEEK, more preferably PEKK. Compared with PEEK, a PEKK is more robust (i.e. less sensitive) to cooling rate, due, at least in part, to a wider range of acceptable crystallinity.

to In one example, the first polymeric composition comprises a reactive thermoplastic resin, such as Elium (RTM). Elium is a liquid monomer that may be processed like a thermoset but upon reaction, transforms into a thermoplastic which may be subsequently thermoformed, melted and/or welded. Anionic polymerization of caprolactam (a monomer of polyamide-6, PA-6) is also suitable. Generally, reactive thermoplastic resins may be cured after laying, for example by heating and/or using a catalyst included in the first polymeric composition, thereby reacting molecules thereof to provide a thermoplastic having improved mechanical properties.

In one example, the first polymeric composition comprises a second thermoplastic, as described above with respect to the first thermoplastic (i.e. a copolymer).

In one example, the first polymeric composition comprises a thermoset, for example an epoxy, benzoxazine, bis-maleimides (BMI), polyimide, polyurethane, silicone, vinyl, amino, furan, phenolic and/or cyanate ester resin, and optionally a hardener.

Selection of an appropriate first polymeric composition for the first reinforcement fibre is known Forming Discontinuities in Reinforcement Fibres -13 -The method comprises forming the first discontinuity of the first set of discontinuities in the first reinforcement fibre of the first tape or tow. It should be understood that the first discontinuity of the first set of discontinuities comprises and/or is a reduction in cross-sectional area and/or diameter of the first reinforcement fibre. Thus, the first discontinuity may be a partial discontinuity, corresponding with a partial reduction in cross-sectional area and/or diameter of the first reinforcement fibre. Alternatively, the first discontinuity may be a full discontinuity, corresponding with parting (i.e. severing) the first reinforcement fibre. In one example, the first discontinuity of the first set of discontinuities in io the first reinforcement fibre comprises and/or is a partial discontinuity, wherein a reduction in cross-sectional area and/or diameter of the first reinforcement fibre is in a range from 10 % to 90 %, preferably in a range from 25 % to 75 %. In one example, the first discontinuity of the first set of discontinuities in the first reinforcement fibre comprises and/or is a full discontinuity. Forming a discontinuity may involve damaging or breaking the reinforcement fibre.

In one example, forming the first discontinuity comprises forming the first discontinuity while spooling the first tape or tow from the first spool. In this way, the first discontinuity is formed in situ (i.e. inline), during layup. In one example, the method comprises forming the first discontinuity of the first set of discontinuities in the first reinforcement fibre in situ. That is, the discontinuities may be formed inline, during the layup.

In one example, forming the first discontinuity comprises forming the first discontinuity at a first predetermined position in the first reinforcement fibre. In this way, the position of the first discontinuity may correspond with a relatively tight arc during steering.

In one example, forming the first discontinuity comprises transversely parting, at least in part, the first reinforcement fibre, for example wherein a reduction in cross-sectional area and/or diameter of the first reinforcement fibre is in a range from 10% to 100%, preferably in a range from 25% to 75%. In -14 -one example, forming the first discontinuity comprises transversely fully parting the first reinforcement fibre.

In one example, forming the first discontinuity comprises laser ablating, electron beam cutting, cutting, shearing and/or punching and/or water jetting, at least in part, the first reinforcement fibre. More generally, in one example, forming the first discontinuity comprises thermally (for example, laser ablating) and/or mechanically (for example cutting, punching and/or water jetting) parting, at least in part, the first reinforcement fibre. In one example, forming the first discontinuity comprises not removing some of the first reinforcement fibre, for to example mechanically by punching and/or water jetting. In this way, tension may be relieved while compression may also be relieved by ends of the first reinforcement fibre sliding past each other. In one example, forming the first discontinuity comprises removing some of the first reinforcement fibre, for example thermally by laser ablating or electron beam cutting and/or mechanically by punching and/or water jetting. In this way, tension may be relieved while compression may be relieved since the gap formed by the discontinuity allows the ends of the first reinforcement fibre to close together.

Methods of laser ablating reinforcement fibres are known. Nanosecond-pulsed UV laser sources are suitable for parting carbon and glass fibres, for example, achieving good quality ablated surfaces without introducing heat damage. Other laser sources are known. In one example, a laser spot size corresponds with a diameter of the first reinforcement fibre.

In one example, forming the first discontinuity of the first set of discontinuities in the first reinforcement fibre comprises providing square and/or tapering ends of the first reinforcement fibre at the first discontinuity therein. In this way, fibre mobility is improved, allowing relatively tight arcs to be steered. In contrast, bulbous ends (i.e. comprising protrusions) of the first reinforcement fibre at the first discontinuity therein may reduce fibre mobility, for example by mutually interlocking, resulting in pull out of the first reinforcement fibre during deposition of such relatively tight arcs.

-15 -Placing Tapes or Tows The method comprises placing the set of tapes or tows, including the first tape or tow having the first discontinuity of the first set of discontinuities formed in the first reinforcement fibre.

Placing of tapes and tows during ATL and AFP is known generally. It should be understood that the set of tapes or tows is placed (for example with a tape/tow laying head, for example a laser assisted tape/tow laying head) on a tool (also known as a mould or a former).

In one example, placing the set of tapes or tows comprises steering the io first tape or tow in a first arc of a set of arcs. In this way, the first tape or tow maybe placed so as to conform with local curvature in two or three dimensions. Particularly, the first discontinuity increases path mobility of the first reinforcement fibre, thereby reducing formation of defects such as wrinkles and/or buckling and hence enabling the first arc to have a relatively small radius of curvature compared with an intact tape or tow. Steering in ATL and AFP is known generally, requiring in-plane curvature of the first tape or tow.

In one example, steering the first tape or tow, having a width W, in the first arc comprises steering the first tape or tow in the first arc having a radius R, wherein R/sqrt(W) is in a range from 10 mm-1/2 to 364 mm, preferably in a range from 50 mm-1/2 to 300 mm, more preferably in a range from 100 mm-1/2 to 200 mm-1/2. In this way, the first arc has a relatively small radius. It should be understood that the radius R is in the plane of the first tape or tow.

W (mm) R (mm) R/sqrt(VV) (mm-1/2) 1/8" (3.175 mm) 650 mm 364.7888 1/2" (6.35 mm) 1300 mm 515.889 1/2" (12.7 mm) 2600 mm 729.578 Table 1: Conventional minimum radius for AFP tows.

-16 -Additionally and/or alternatively, where the discontinuities are used to provide graded properties such as for aeroelastic tailoring, or tailored damping, steering the first tape or tow may not be required.

Second Discontinuity In one example, the method comprises forming a second discontinuity of the first set of discontinuities in the first reinforcement fibre, wherein the first discontinuity of the first set of discontinuities and the second discontinuity of the first set of discontinuities are mutually spaced apart axially.

In one example, the method comprises forming a second discontinuity of io the first set of discontinuities in the first reinforcement fibre, for example spaced apart axially from the first discontinuity by a spacing S. That is, the spacing S is a continuous length (i.e. not including any discontinuities) of the first reinforcement fibre between the first discontinuity and the second discontinuity therein. In one example, the spacings is greater than or equal to a critical length ic of the first reinforcement fibre in the filament, preferably wherein S > 31, more preferably wherein S > 5C, most preferably wherein S > 7le. For example, for carbon fibres, the spacing S between the first discontinuity and the second discontinuity may be as low as 2 mm (for improved flexibility), equating to about 4C. Preferably, the spacing S between the first discontinuity and the second discontinuity is greater than about 41. However, there is only marginal benefit by comparing average fibre length in a range of 50 to 500mm or above.

In one example, forming the second discontinuity of the first set of discontinuities in the first reinforcement fibre comprises forming the second discontinuity of the first set of discontinuities in the first reinforcement fibre while placing the first tape or tow, including the first discontinuity of the first set of discontinuities formed in the first reinforcement fibre. In this way, the discontinuities are formed in situ i.e. upstream of the layup, for example immediately prior to placement.

-17 -Second Tape or Tow In one example, the set of tapes or tows includes a second tape or tow comprising a second set of reinforcement fibres, including a first reinforcement fibre; forming a first discontinuity of a second set of discontinuities in the first reinforcement fibre of the second tape or tow.

In one example, forming the first discontinuity in the first reinforcement fibre of the first tape or tow comprises forming discontinuities in the first set of reinforcement fibres across a width of the first tape or tow, for example based io upon a predetermined radius of curvature of an arc, or range thereof, through which the first tape or tow will be steered, for example wherein a relatively higher number, density and/or number density of discontinuities is formed relatively more proximal inner and/or outer edges of the tape or tow while a relatively lower number, density and/or number density of discontinuities is formed relatively more distal the inner and/or outer edges. In one example, forming the first discontinuity in the first reinforcement fibre of the first tape or tow comprises forming discontinuities in the first set of reinforcement fibres, wherein a distribution of the discontinuities varies across a width of the first tape or tow, for example wherein the discontinuities are preferentially formed relatively more proximal inner and/or outer edges of the tape or tow than formed relatively more distal the inner and/or outer edges In this way, steerability may be improved. In one example, forming the discontinuities in the first set of reinforcement fibres across the width of the first tape or tow comprises controlling a spacing, a location and/or a density of the discontinuities. For example, the spacing and/or density of the discontinuities may be preferentially controlled to increase steerability (e.g. relatively more discontinuities near or at the outer and/or inner arcs and relatively fewer near or at the neutral axis). In other words, the number, density and/or number density of discontinuities may be graded across a width of the first tape or tow.

-18 -Apparatus The second aspect provides an apparatus for layup for fibre-reinforced composite parts from, at least in part, a set of tapes or tows, including a first tape or tow, wherein the first tape or tow comprises a first set of reinforcement fibres, including a first reinforcement fibre, the apparatus comprising: means for forming a first discontinuity of a first set of discontinuities in the first reinforcement fibre of the first tape or tow; and means for placing the first tape or tow having the first discontinuity of the first set of discontinuities in the first reinforcement fibre of the first tape or tow.

io Apparatuses for ATL and AFP are known. In one example, the apparatus comprises an ATL apparatus. In one example, the apparatus comprises an AFP apparatus.

The fibre-reinforced composite parts, the set of tapes or tows, the first tape or tow, the first set of reinforcement fibres, the first reinforcement fibre, the first polymeric composition, the first discontinuity and/or the first set of discontinuities may be as described with respect to the first aspect.

In one example, the means for forming the first discontinuity comprises thermal means (for example, laser ablating) and/or mechanical means (for example cutting, punching and/or water jetting).

In one example, the apparatus comprises a controller arranged to control a position of the first discontinuity of the first set of discontinuities in the first reinforcement fibre, for example by controlling the means for forming the first discontinuity.

In one example, the means for placing the first tape or tow comprises means for steering the first tape or tow, e.g. a steering mechanism in an end effector. The methods and apparatus of the present invention enhance the performance of such a steering mechanism, advantageously allowing the tapes and/or tows to be steered over tighter radii.

-19 -Fibre-reinforced Composite Part The third aspect provides a fibre-reinforced composite part (also known as an article), or a precursor thereof, manufactured, at least in part, according to the method of the first aspect, using the tape or tow according to the fourth 5 aspect and/or using the apparatus according to the second aspect.

In one example, the part comprises and/or is an aircraft, an aerospace component, a land craft or a sea craft component.

Tape or Tow The fourth aspect provides a tape or tow, comprising a first set of io reinforcement fibres, including a first reinforcement fibre; wherein the first reinforcement fibre comprises a first discontinuity of a first set of discontinuities therein.

In one example, the tape or tow includes a predetermined distribution of discontinuities, for example based upon a predetermined radius of curvature, or range thereof, of an arc through which the tape or tow will be steered, for example wherein a relatively higher number, density and/or number density of discontinuities is formed relatively more proximal inner and/or outer edges of the tape or tow while a relatively lower number, density and/or number density of discontinuities is formed relatively more distal the inner and/or outer edges. In one example, the tape or tow includes a predetermined distribution of discontinuities, wherein the distribution varies across a width of the first tape or tow, for example wherein the discontinuities are preferentially relatively more proximal inner and/or outer edges of the tape or tow than relatively more distal the inner and/or outer edges In this way, steerability may be improved. In one example, the distribution of the discontinuities, for example a spacing, a location and/or a density of the discontinuities, in the first set of reinforcement fibres across the width of the first tape or tow is controlled. For example, the spacing and/or density of the discontinuities may be preferentially controlled to increase steerability (e.g. relatively more discontinuities near or at the outer and/or inner -20 -arcs and relatively fewer near or at the neutral axis). In other words, the number, density and/or number density of discontinuities may be graded across a width of the first tape or tow. In one example, the tape or tow is provided on a spool i.e. pre-manufactured. This would be a cheaper alternative to in situ forming of the discontinuities and will enable users to change over to the modified tape for specific regions of the layup where steerability and/or graded properties is critical.

The tape or tow, the first set of reinforcement fibres, the first reinforcement fibre, the first polymer composition, the first discontinuity and/or the first set of discontinuities maybe as described with respect to the first aspect.

Method of Manufacturing The fifth aspect provides a method of manufacturing a fibre-reinforced composite part, the method comprising: laying up of the fibre-reinforced composite according to the first aspect or the fourth aspect; and providing a matrix, comprising a first polymeric composition, for the layup.

Methods of manufacturing fibre-reinforced composite parts from layups are known The method may include any of the steps described herein.

For example, the method may involve placing the set of tapes or tows, including the first tape or tow having the first discontinuity of the first set of discontinuities formed in the first reinforcement fibre, wherein the placement comprises laying the set of tapes or tows on a tool (for example using a laying head).

The method of manufacturing fibre-reinforced composite pads may further comprise repeating the layup for a further layer or set of layers (in the same or differing directions) until the required fibre-reinforced composite part is produced. -21 -

Depending on the type of fibre-reinforced composite being produced, the fibre-reinforced composite part may be placed in an autoclave for curing, therein producing the final part.

The first polymeric composition may be as described with respect to the first aspect.

In one example, a volume fraction of the first set of reinforcement fibres is in a range from 10% to 70%, preferably in a range from 20% to 65%, for example 30%, 40% or 50%, by volume of the fibre-reinforced composite part.

Definitions to Throughout this specification, the term "comprising" or "comprises" means including the component(s) specified but not to the exclusion of the presence of other components. The term "consisting essentially of or "consists essentially of" means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention, such as colourants, and the like.

The term "consisting of" or "consists of' means including the components specified but excluding other components.

Whenever appropriate, depending upon the context, the use of the term "comprises" or "comprising" may also be taken to include the meaning "consists essentially of or "consisting essentially of', and also may also be taken to include the meaning "consists of" or "consisting of'.

The optional features set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional features for each aspect or exemplary embodiment of the invention, as set out herein are also applicable to all other aspects or exemplary embodiments of the invention, where appropriate. In other words, the skilled person reading this specification -22 -should consider the optional features for each aspect or exemplary embodiment of the invention as interchangeable and combinable between different aspects and exemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, and to show how exemplary embodiments of the same may be brought into effect, reference will be made, by way of example only, to the accompanying diagrammatic Figures, in which: Figure 1 schematically depicts a method according to an exemplary to embodiment; and Figure 2 schematically depicts a method according to an exemplary embodiment, in more detail;

DETAILED DESCRIPTION

Figure 1 schematically depicts a method according to an exemplary embodiment.

The method is of layup, for example ATL or AFP, for fibre-reinforced composite parts.

At S101, the method comprises providing a set of tapes or tows, including a first tape or tow, wherein the first tape or tow comprises a first set of reinforcement fibres, including a first reinforcement fibre.

At 5102, the method comprises forming a first discontinuity of a first set of discontinuities in the first reinforcement fibre of the first tape or tow.

At 5103, the method comprises placing the set of tapes or tows, including the first tape or tow having the first discontinuity of the first set of discontinuities formed in the first reinforcement fibre.

-23 -Figure 2 schematically depicts a method according to an exemplary embodiment, in more detail.

At S201, the method comprises providing a set of tows 10, including a first tow 10A, wherein the first tow 10A comprises a first set of reinforcement fibres 100, including a first reinforcement fibre 100A.

In this example, the first tow 10A has a width of% inch (12.7 mm). In this example, the first set of reinforcement fibres 100 comprises carbon fibres io particularly aerospace grade IM7, having a diameter of 5.2 pm. In this example, the first reinforcement fibre 100A comprises and/or is a continuous fibre.

In this example, providing the set of tows 10 comprises spooling the first tow 10A from a first spool (not shown).

In this example, the first set of reinforcement fibres 100 includes a second reinforcement fibre 100B. In this example, the first set of reinforcement fibres includes a third reinforcement fibre 100C, a fourth reinforcement fibre 100D and a fifth reinforcement fibre 100E. In this example, the first tow 10A is a 6K tow i.e. including 6,000 reinforcement fibres.

At S202, the method comprises forming a first discontinuity 110A of a first set of discontinuities 100 (shown generally as filled circles) in the first reinforcement fibre 100A of the first tow 10A.

In this example, the first set of reinforcement fibres 100 includes the second reinforcement fibre 100B and the method comprises forming a first discontinuity of a second set of discontinuities in the second reinforcement fibre 100B, wherein the first discontinuity of the first set of discontinuities and the first discontinuity of the second set of discontinuities are mutually spaced apart axially.

-24 -In this example, forming the first discontinuity 110A comprises transversely parting, at least in part, the first reinforcement fibre 100A, wherein a reduction in cross-sectional area and/or diameter of the first reinforcement fibre 100A is in a range from 30 % to 100%.

In this example, forming the first discontinuity 110A comprises laser ablating, at least in part, the first reinforcement fibre 100A.

In this example, forming the first discontinuity 110A of the first set D1 of discontinuities 110 in the first reinforcement fibre 100A comprises providing tapering ends of the first reinforcement fibre 100A at the first discontinuity 110A io therein.

In this example, forming the first discontinuity 110A comprises forming the first discontinuity while spooling the first tow 10A from the first spool.

In this example, the method comprises forming a second discontinuity 110B of the first set D1 of discontinuities 110 in the first reinforcement fibre 100A, spaced apart axially from the first discontinuity 110A by a spacing L. In this example, the spacing L > 5/c.

In this example, forming the first discontinuity 110A in the first reinforcement fibre 100A of the first tow 10A comprises forming discontinuities in the first set of reinforcement fibres 100 across a width W of the first tow 10A, based upon a predetermined radius of curvature of an arc R3 through which the first tow 10A is steered, for example wherein a relatively higher number, density and/or number density of discontinuities is formed relatively more proximal inner and/or outer edges of the tow 10A while a relatively lower number, density and/or number density of discontinuities is formed relatively more distal the inner and/or outer edges. In this example, forming the first discontinuity 110A in the first reinforcement fibre 100A of the first tow 10A comprises forming discontinuities in the first set of reinforcement fibres 100, wherein a distribution of the discontinuities varies across a width of the first tow 10A, for example wherein the discontinuities are preferentially formed relatively more proximal inner and/or -25 -outer edges of the tow 10A than formed relatively more distal the inner and/or outer edges In this way, steerability may be improved. In this example, forming the discontinuities in the first set of reinforcement fibres 100 across the width of the first tow 10A comprises controlling a spacing, a location and/or a density of the discontinuities. For example, the spacing and/or density of the discontinuities may be preferentially controlled to increase steerability (e.g. relatively more discontinuities near or at the outer and/or inner arcs and relatively fewer near or at the neutral axis R3). In other words, the number, density and/or number density of discontinuities may be graded across the width W of the first tow 10A.

io Preferably the discontinuities are not distributed along the whole length of a radius. Preferably, in order to steer a tape or tow around an in-plane corner during lay-up, the discontinuities are introduced near or at the outer and/or inner sides of the arc away from the neutral axis of the tape or tow (i.e. to enable some stretch in the outer arc segments and prevent internal stresses that cause buckling around the inner arc).

At 5203, the method comprises placing the set of tows 10, including the first tow 10A having the first discontinuity of the first set of discontinuities formed in the first reinforcement fibre 100A.

In this example, placing the set of tows 10 comprises steering the first tow 10A in a first arc R1 of a set of arcs. In this way, the first tow 10A may be placed so as to conform with local curvature in two or three dimensions. Particularly, the first discontinuity increases path mobility of the first reinforcement fibre 100A, thereby reducing formation of defects such as wrinkles and/or buckling and hence enabling the first arc to have a relatively small radius of curvature compared with an intact tow. Steering in ATL and AFP is known generally, requiring in-plane curvature of the first tow 10A.

In this example, the reinforcement fibres 100A to 100E are steered about radii R1 to R5 respectively, wherein R1 < R2 < R3 < R4 < R5; wherein R1 is proximal the inner radius, R3 corresponds with the neutral axis and R5 is proximal the outer radius.

-26 -In this example, the third reinforcement fibre 100C, steered about R3 and corresponding with the neutral axis, includes no discontinuities. In contrast, the first and fifth reinforcement fibres 100A, 100E, steered about radii R1 and R5 respectively and corresponding with quasi maximum compression and tension respectively across with the width W of the first tow 10A, include relatively high number densities of discontinuities. The second and fourth reinforcement fibres 100B, 100D, steered about intermediate radii R2 and R4 respectively and corresponding with intermediate compression and tension across with the width W of the first tow 10A, include relatively low number densities of discontinuities.

io In this example, steering the first tow 10A, having the width W, in the first arc comprises steering the first tow 10A in the first arc having a radius R3, wherein R/sqrt(VV) is in a range from 100 rnm-% to 200 mm-Y2. In this way, the first arc has a relatively small radius. It should be understood that the radius R3 is in the plane of the first tow 10A and is the mean radius.

Although a preferred embodiment has been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims and as described above.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at most some of such features and/or steps are mutually exclusive.

-27 -Each feature disclosed in this specification (including any accompanying claims, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims and drawings), or to any novel one, or any novel to combination, of the steps of any method or process so disclosed.

Claims

-28 -CLAIMS1. A method of tape or tow steering in the lay-up of fibre-reinforced composite parts, the method comprising: providing a set of tapes or tows, including a first tape or tow, wherein the first tape or tow comprises a first set of reinforcement fibres, including a first reinforcement fibre; forming a first discontinuity of a first set of discontinuities in the first reinforcement fibre of the first tape or tow; and to placing the set of tapes or tows, including the first tape or tow having the first discontinuity of the first set of discontinuities formed in the first reinforcement fibre.
2. The method according to claim 1, wherein providing the set of tapes or tows comprises spooling the first tape or tow from a first spool.
3. The method according to claim 2, wherein forming the first discontinuity comprises forming the first discontinuity while spooling the first tape or tow from the first spool.
4. The method according to any previous claim, wherein forming the first discontinuity comprises forming the first discontinuity at a first predetermined position in the first reinforcement fibre.
5. The method according to any previous claim, wherein forming the first discontinuity comprises transversely parting the first reinforcement fibre.
-29 - 6. The method according to any previous claim, wherein forming the first discontinuity comprises laser ablating, electron beam cutting, cutting, shearing and/or punching or water jetting the first reinforcement fibre.
7. The method according to any previous claim, wherein placing the set of tapes or tows comprises steering the first tape or tow in a first arc of a set of arcs.
8. The method according to claim 7, wherein steering the first tape or tow, lo having a width W, in the first arc comprises steering the first tape or tow in the first arc having a radius R, wherein R/sgrt(VV) is in a range from 50 rnm-% to 300 mm-%.
9. The method according to any previous claim, comprising forming a second discontinuity of the first set of discontinuities in the first reinforcement fibre, wherein the first discontinuity of the first set of discontinuities and the second discontinuity of the first set of discontinuities are mutually spaced apart axially.
10. The method according to claim 9, wherein forming the second discontinuity of the first set of discontinuities in the first reinforcement fibre comprises forming the second discontinuity of the first set of discontinuities in the first reinforcement fibre while placing the first tape or tow, including the first discontinuity of the first set of discontinuities formed in the first reinforcement fibre.
11. The method according to any previous claim, wherein the first set of reinforcement fibres includes a second reinforcement fibre and wherein the method comprises forming a first discontinuity of a second set of discontinuities in the second reinforcement fibre, wherein the first discontinuity of the first set of -30 -discontinuities and the first discontinuity of the second set of discontinuities are mutually spaced apart axially; and forming a first discontinuity of a second set of discontinuities in the first reinforcement fibre of the second tape or tow.
12. The method according to any previous claim, wherein forming the first discontinuity in the first reinforcement fibre of the first tape or tow comprises forming discontinuities in the first set of reinforcement fibres across a width of the first tape or tow.
13. The method according to any previous claim, wherein the first set of reinforcement fibres is surrounded with a first polymeric composition.
14. A tape or tow, comprising a first set of reinforcement fibres, including a first reinforcement fibre; wherein the first reinforcement fibre comprises a first discontinuity of a first set of discontinuities therein; wherein the tape or tow includes a predetermined distribution of discontinuities based upon a predetermined radius of curvature of an arc through which the tape or tow will be steered.
15. An apparatus for tape or tow steering in the layup of fibre-reinforced composite parts from, at least in part, a set of tapes or tows, including a first tape or tow, wherein the first tape or tow comprises a first set of reinforcement fibres, including a first reinforcement fibre, the apparatus comprising: means for forming a first discontinuity of a first set of discontinuities in the first reinforcement fibre of the first tape or tow; and -31 -means for placing the first tape or tow haying the first discontinuity of the first set of discontinuities in the first reinforcement fibre of the first tape or tow.