CA1229783A - Composite laminate joint structure and method and apparatus for making same - Google Patents

Abstract

Abstract:
The invention provides a composite laminate joint structure for joining articles, e.g. pipes, made of multiple ply composite laminates, and a method for forming such a joint structure. The joint structure comprises a first ply of strands disposed perpendicularly to the axis of the structure, this ply having an exterior surface at one end tapered at an angle of between 5° to 15° when viewed in cross-section relative to the axis. A second ply of strands disposed transversely of the first ply overlies the first ply and extends generally axially.
The second ply has a taper where it overlies the end of the first ply. A third ply of strands is disposed transversely of the second ply and overlies the second ply to extend perpendicularly to the axis. The third ply has a flange on the tapered end of the second ply.
A hardened adhesive impregnates and bonds all three plies together in a common bonding matrix to maintain the flanged and tapered end configuration.

Description

97~33 Description Co!n~osite Laminate Joint Structure and Method and APparatus for Making Same Technical Field This invention relates generally to a composite laminate joint structure, including a method and apparatus for making same, and more particularly to a multiple ply compositeistructure containing a sandwiched ply of longitu~inally oriented bundles of ~0 continuous filament strands which are tapered at an angle between 5 and 15 degrees at one or both ends of the structure to enable the across-strand shear strength of each longitudinally-oriented filament ply bundle to be increased so it equals the tensile strength of the filament bundle. Composit:e laminate joint structures made in accordance with the speci-fications taught in this invention wi.ll exhibit. a joint tensile strength that is soverned primarily by the tensile strength of the lam~nate longitudinally directed filaments rather than by the interlaminar shear strength of the laminate matrix material.

Backqround of the Invention This invention relates to an criented fiber composite structure adapted for use in a wide variety of sealing and load transfer applications and to a method and apparatus for making same. A material havinq two or more distinct constituent materials is a composite material. Composite materials consist of one or more discontinuous phases embedded in a continuo~s phase. The discontinuous phase is usually harder and stronger than the continuous phase and is calied the REI~lFORCEME~T, whereas the continuous phase is termed the MATRIX. A composite material is produced when the volume fraction of the reinforcement exceeds ten percent and when the property of one constituent is at least five times greater than that of the other. Composit.e materials characteristically exhibit significant property changes as a result of the combination of reinforcement and rna-rix materials.

-2-~ ,2~7~3 Fiber Reinforced Plastic (FRP) cornposite structures belong to one of two categories, depending upon whether or not the fiber reinforcement consti-tuents ale tensioned during fabrication of the composite structure. One category to which FRP
composite structures belong is referred to as the Loose Fiber Reinforced Plastic (Ll'RP) category. The LFRP composites include those fabricated from chopped strand fibers, random oriented fiber mat, surfacing - 1~ veil, felt-like fabrics, milled fibers or woven cloth.
The other category is referred to as the Tensioned Filament Reirlforce(3 Plastic (TFRP) category. The TFRP composites include those fahricated from continuous unidirectional filament strands which are 1~ collimated, oriented and tensioned during the fabri-~ cation process. The TFRP composites are made by the - pultrusion method, by the filament winding method, or by the combination of these two methods ~nown as the "I.ONGO-CIRC" method. Pultruded TFRP composites include those containing continuous unidirectional collimated filament reinforcements which are tensioned ~"hile the filaments are pulled through extrusion dies which form the composite into structural shapes, such as angles or tees, of nearly any length.
Pultruded composite structures primarily comprise tensioned "L~NGCS", the name given by the American Society of Mechanical Engineers (ASME) in Section X
of the Boiler and Pressure Vessel Code to longi-tudinally oriented filament reinforcements. Filament wound composites, on the other hand, primarilv consist of tensioned "CIRCS", the ASME name given to circum-ferentially wound filament reinforcements. This invention includes the class of TFRP cormposites which contain both LONGOS and CIRCS and particularly t.ubular laminate structures fabricated in accordance wit.h the "parabolic tensioning" methods taught by U.S. patent 3,784,441. The tubular larninate structures cescribed by the specifications and illustrations of the present invention are ideally suited to serve as pipe, truss and tank structures and can resist internal pressure loads and the longidudinal and circum-ferential stresses which are simultaneously imposed , .
upon the tubular laminate plies.
Prior art methods for joining tubular filament : wound laminates subjectedi to longitudinal stresses have . 5 a joint bond strength that can never exeeed the inter-laminate shear strength of the plastic matrix material used to bond the laminate plies and their constituent filament reinforcernents. The longitudinal loads transferred through bolted flanges, ~hreaded ends and other prior art mechanical methods used to join and disconnect tu~ular laminate struc~ures are limi~ed by the shear strength of the adhesive material used to bond the flanges, threads or other joint rnaking structures to the end portions of the tubular laminate.
The shear strength limitations characteri%ing plastic - matrix or bonding material, restrict, if not prevent, the use of prior art tubular laminate structures to applications where high strength mechanical joints are required. Prior art methods employed to mechanically join and seal tubular laminate structures include threaded ends and flanged ends. Threaded ends used to mechanically join and seal composite pipe of rein-forced plastic are generally weaker and less wear resistant than composite flanged-ended counterparts of equivalent size and service. For this reason flanged ends are commonly employed to mechanically join and seal prior art tubular laminate structures ; which are highly stressed. Such flanges are Erequently fabricated as separate structures which are bonded -to specially prepared end portions of the composite tubes.
Other flanges are filament wound or otherwise fo,-med directly upon ends as an integral part of the composite tube structure Prior art methods which employ these types of threaded or flanged ends to mechanically join and seal tubular laminate structures are limited by the interlaminate shear strength of the plastic matrix material used to fabricate threaded or flanged laminate structures or by the shear strength of the adhesive material used to bond preabricated threaded or flanged structures to the ends of tubular laminate -4~

~2297~3 structures For this reason prior art cornposite structures which mechanically join and seal tubular ' laminate structures possess a longitudinal tensile end-load resistance capability which is governed by flange thic~ness, thread root section area or the adhesive surface area employed in bonding the joint structure rather than upon the thic~ness of certain tubular laminate plies.
Panel laminate structures fabricated in accordance with specifications outlined in the present invention are ideally suited to serve as easily assembled integral elements of monolithic wall or roof structures.
Prior art methods for joining flat or curved composite laminate panels generally involve bonding, clamping, riveting or bolting the panels. The prior art panel joining methods prevent the joint strenqth to equal a panel's maximum tensile and bending strength. This is because the strength of bonded or clamped joints is limited by the interlaminate shear strength of the adhesive material bonding the laminate plies. The strength of bonded and clamped joints is especially diminished when panel joints are flexed or twisted in a manner which imposes peel stresses upon the adhesive bonding material. The strength of bolted or riveted panel joints, although possibly superior to bonded joints, is limited by the tear out, bearing or crush strength of the laminate composite material.
These prior art panel joining methods do not enable panel joints to be made which are flush with the joined panels.
:
Disclosure of the Invention A primary object of the present invention is to overcome the briefly described prior art problems and restrictions by providing a composite laminate joint structure which enables mechanically joining multiple ply composite laminates so that the joint tensile strength approximately equals the combined tensile strength of the laminate Structure filament strands which are oriented parallel to the principal di~ection of the joint tc-nsile stress.

~L2~97~3~

l~no~her object of his invention is to disclose how unidirectional continuous filament strands can be positioned to increase the across - strand shear -trength of the individual filament strands by a factor of at ]east four and thereby enable a shear load applied to the unidirectional filament strands to be primarily resisted by the tensile strenqth of the filament strands.
rrhe rnethod and apparatus for making such a composite laminate joint structure may comprise - the following steps:

1. Coating a cylindrical mandrel and any seal forming appurtenants with a suitable resin release agent.
. .
; 2. Fabricating upon the coated mandrel and any seal forming appurtenants an impermeable inner . liner structure from a combination of woven and non-woven fiber reinforcemellts impregnated with a t resin.

- 3. Placing upon the liner structure a first ply of circumferentially oriented continuous filament strands which are impregnated with a liquid thermo-setting polymeric resin and forming at each extremity of the first ply an inwardly tapered conical laminate support structure having sufficient thickness to provide a taper angle of at least 8 degrees.

4. Placing upon the first ply filament strands a second ply of unidirectional longitudinal continuous filament strands which are impregnated with a liquid therrnosetting polymeric resin and oriented approxi-mately parallel to the mandrel turning axis, the ends of the longitudinal filament strands being secured by a series of protruding pins or hooks which are uniformly spaced around each of the pin support rings ~ocated at the extremities of the mandrel.

~22978~

5. Placing ul~on the second ply filalllent s~rands a third ply of circumferentially oriented continuous filament strands which are irnpregnated with a li~uid helmosetting plastic resin and which tension and pre~ss the second ply filament strands fi{lllly a~lainst the first ply filament strands to ro!-m at each end, against removahle flange forming s~lucl.ules, a ~langed configuration suitable for mec~)anically connec~ing the completed composite !aminate joint struct.ul-e to other composite laminate joint str~lctules

6. At least partially curing and hardening . the resin to maintain all filament strands in tension and disconnecting the ends of the second ply longi-tudinai.filament strands from pins or hooks ernployed to secure the ends of the second ply filament stands.

7. Fully curing and hardening the thermo-setting l-esin matrix ana removing the composite laminate joint structure from the mandrel and any seal formins app~rtendnts, One aspect of the invention provides an appa-ratus for forming a composite laminate joint structure thereon comprising a mandrel comprising separate parts releasably attached together in axial alignment by fas-tening means, said mandrel mounted on a longitudinal axisthereof and having an annular cross section throughout its length, at least one~pair of annular filament strand grippin~ means spaced apart longitudinaliy on the peri-pherv o~ one of the parts of said mandrel, each of said gripping means extending radially outwardly from said axis and terminating at a convex surface, the radial heights of ~Z2~7~33 said gri~pilly means being suf~icient to enable long1tua-inally disvosed filament strands attached to said gripping means to be formed into a composite laminate having a tapered end configuration, at least one removable annular flange forming means adapted to be positioned adjacent to the in~ard angle-forming edge of a tapered laminate comprising an end portion of a multiple ply composite laminate struct~re formed upon said mandrel.
Other aspects of this invention are claimed in my co-pending Canadian patent application Serial No. 419,171 filed on January 10, 1983, of which the present applica-tion is a division.
srief Description of the Dra~,ings Further objects of this invention will become appaLell~ fl-om the follo~ing description and accompanying dra~:ings ~!herein:

FIG. 1 displays the principal dimensional design paL-ameters of an idealized section of an end of a composite laminate joi.nt structure comprised of a t~pered laminate ply structure sandwiched bet~een a tanc-red support structure and a flanged load-inducing structure in accordance with the teaching or this ir,vention .

-7a-12~97~;~

FIG. 2 is a perspective view of FIG. 1 illustrating the principal pressures and stresses imposed upon the structural constituents of a unit width of a composite laminate joint structure subjected to a representative loading condition.

FIG 3 schematically illustrates the relationship between the principal structural elements of the representative laminate joint structure depicted in FIG. 2 and the principal resulting load vec tors.

FIG 4 is an enlarged Eragmentary perspective view depicting the arrangement of filarnent reinforce-ments in the laminate plies which comprise an endportion of a composite laminate joint structure made in accordance with the teaching of this invention.

; FIG. 5 is a partially sectioned side 20 elevation view of an assembly of tubular composite laminate joint structures used in conjunction with appropriate pressure sealing and connecting structures to illustrate a pipe coupling embodiment of this - invention.
c 25 FIG. 6 is an exploded perspective view of a pipe joint embodiment of this invention employing a segmented coupling structure assembly similar to that depicted in FIG. 5.
., .
Description of the Preferred Embodiment FIGS. 1 2 and 3 schematically illustrate the dimensional parameters and vector analyses associated with the three principal structural elements 5 comprising an end portiOn of Che composite lamin~te ,, .

c "
., ~2%9~
joint structure which represents the preferred embodiment of this invention.
The composite laminate joint structure in its broadest application comprises at least one end portion consisting of a first ply tapered support structure 2a, having a taper angle "a"upon which is formed a tapered-end second ply structure la having a laminate thickness "T" and a taper angle a'. The second ply laminate structure comprises continuous filaments 1 \r~hich are oriented approximately parallel -to the direction of the resisting tensile load vector Tx. A third ply laminate structure 3a is .
formed upon the tapered end portion of the second ply laminate and configured to form a flanged structure which communicates an impressed unit joint load Px directly to the filament reinforcements 1 comprising the tapered end portion of the second ply laminate structure 1a.
Each filament of each strand is preferably continuous and each strand preferably contains from 204 to 12,240 (one end to 60 end) individual filarnents.
The filaments may be inorganically (glass, metal carbon, etc.) or organically (aramid, polyamide, fluorocarbon, etc.) composed. The preferred filament for the hereinafter described structures constitutes glass having an O.D. of 0.00095 inch or less. The preferred glass filament strand for making the hereinafter described structures has a yield of 225 to 250 yards of strand length per pound and a minimum-dry breaking strength of from 190 to 250 pounds .
The hereinafter more fully described hardened "adhesive means", or "composite matrix material"
used for bonding strands of superimposed lami.nate ~ plies together, may be selected from the broad group of available thermosetting or thermoplastic resin materials as ~lell as certain inorganic bonding ~2297~3 liquids and hydraulic cements suitably composed for such bonding purposes. As is well known in the art, the thermosetting resins may be polyesters, vinylesters, furans, epoxies, phenolics , polyurethanes, S silicones or any suitable mixture thereof. The thermoplastic resins rnay comprise polyethylene, polypropylene, aramid, or fluorocarbons. The inorqanic bonding liquids may comprise the consti-tuents of magnesium oxychloride or sirnilar hydraulic cements. The polyesters, vinylesters and epoxies are normally utilized in the hereinafter described examples since they are relatively available easily used and s~iitable for many composite structure applications.
The forming apparatus for the cornposite laminate joint structure is typified by a removable forming surface or mandrel which may include a pair of LONGO strand attachment rings each of which comprise an annular array of strand hooks positioned at each end of the mandrel.
The forming apparatus may also include at least one separable annular forming unit secured to the mandrel during laminate fabrication. The annular forming unit may be used to govern the end thickness and configuration of the tapered first ply support structure and to guide the fabrication of a first ply support structure having the desired angle of taper.
The preferred embodiment of this invention exhibits how the unidirectional continuous filament strands which resist an applied joint tensile load can be positioned in a composite laminate joint structure in a manner that increases the "across strand"
shear path and concomitajntly increases the "across strand" shear area and the net "across strand" shear strength of the continuous filament strands. The basic "across strand" shear strength of continuous filament strands can be determined by rneasuring the force required to punch a hardened steel die through a laminate sheet comprised of unidirectional continuous ~%;~:97~
filaments bonded togethcr ~Jith a hardened thermosetting resin and oriented in a plane perpendicular to the punch shear force direction. The basic "across strand"
shear strength of the continuous filament strands equals the punch shear force divided by the product of the die punch circumference and the laminate sheet thic~ness. It has been determined that a shear force of approximately 6600 pounds is r~luired to punch out a composite laminate section having a circumference of approximately 3 inches from a laminate approxi-mately 0.10 inch thic~ comprised to a volume fraction of at least 45 percent of unidirectional continuous glass filament reinforcements oriented parallel to the faces of the laminate sheet and perpendicular to the die punch shear force. From such tests it has been determined that the "across strand" shear strength of continuous glass filaments is approximately one fourth the maximum tensile strength of filament strands loaded in a direction parallel to their longitudinal axis. ~Jhen the "across strand" shear path of a laminate comprised of unidirectional filament strands is increased so that the shear path length equals or exceeds four times the laminate thic~ness the maximum shear force resisted by the filament strands is no longer governed by the combined "across strand" shear strength of the individual filament strands but is determined instead by the combined tensile strength of the individual filament strands.
FIG. 1 illustrates in cross section the arrangement and configuration of the three principal structural elements comprising an end portion of the preferred embodiment of the present invention.
FIG. 1 also identifies the three dimensions ~1hich principally govern the strength per unit ~-idth of the depicted compOsite laminate joint structure. The first ply laminate support structure 2a is the principal _ 1 1 _ ~ ~97~33 end portion of the composite laminate joint structure and is configured to have a taper equal to the angle "a". The second ply laminate structure, 1a, has a laminate thic~ness "T" and a taper angle equal to that of the laminate support structure 2a. The third ply laminate structure 3a is configured to firmly contact the tapered laminate ply, 1a, and to provide a flanged joint end structure sufficiently rigid to enable the tapered laminate s~ructure 1a to resist a unit tensile joint load along the shear plane having a shear path length equal to the "S" dimension.
Table I helow illustrates how the taper angle "a"
governs the length of the "across strand" shear path, "S" for a given thickness, "T" of the second ply laminate structure, 1a. This relationship is expressed by the formula S = T / sin "a".
TABLE I
TAPER A~GLE "a" ACROSS STRAND
(Degrees)SHEAR PATH LENG'rl~, "S"
. ~
2 28.6 T
11.5 T
5.8 T
3.9 T
2.3 T
2.0 T
1.4 T
1.2 T

Table I illustrates that ~3hen the end portion of the second ply laminate structure, 1a, is configured to have a taper angle between 5 and 15 the "across strand" shear stress imposed upon the continuous filament strands comprising the second ply laminate structure becomes less than the tensile stress imposed upon the same strands. Tensile loads resisted by a cornposite laminate joi.nt structure similar to that illustrated in EIG. 1 are thus governed by 97~3 the combined tensile strength of the continuous filament strands comprising the second ply laminate structure.
FIG. 2 is an ideali2ed perspective view of a unit width of the end portion of a composite laminate joint structure. The end portion of the laminate ply structure lb is assumed to have a taper angle "a" greater than 5 degrees and less than 10 degrees. The unit tensile joint load, Px, which is imposed upon a unit width of the third ply flange structure 3b is resisted by an equal and opposite tensile load, Tx, imposed upon the unidirectional continuous filament strands comprising a unit width of the laminate ply structure 1b. FIG. 2 illustrates that the unit load, Px acting upon the wedge-shaped flange structure 3b requires a unit compression force equal to Py to assure the second ply laminate structure, lb, continues to resist the unit tensile load, Tx. The unit compression force, Pv, imposed upon the third ply flange structure is resisted by an equal and opposite compression force,~y, acting upon the first ply -laminate support structure, 2b.
Table II below illustrates how the magnitude of the compression force, Py, decreases with respect to a given tensile force Px, as the taper anc;le "a"
increases. This relationship is-expressed by the formula P y = P x / tan "a".
TABLE II
. . .
TAPER ANGLE "a"CO~lPRESSIOI~ FORCE, "Py"
(Degrees) _ 11.4 Px 5.7 Px 3.7 Px 1.7 Px 1.0 Px 0.6 Px FIG. 3 is a schematic diagram of vectors imposed upon the three principal structural elements comprising the composite laminate joint structure -13~

~2,~978.3 configured to repl-esent a prefel-red c-mbo(1iment of he pres~nt invention. rable III below illustrates ho~
an increase in the taper angle a serves to increase the resultant tensile stress ~. It should be noted that the tensile strength oE the composite laminate joint structure of the present invention is governed by the unit resultant tensile force, ~, imposed upon the continuous filament strands comprising the tapered end portion of the laminate structure 1c. As may be noted, for low taper angles ~B approximately equals Tx. This relationship is expressed by the formula T R = T x / cos a .
_ABLE III
TAPER ~NGLE a RES~LTANT TE~SILE
(~egrees) ¦STRESs rR
-1.00 Tx 1.02 Tx 1.04 Tx 1.15 Tx 1.41 Tx 2.00 Tx Exam~le_1 ~ IG. 4 depicts; the end portion of a multiple ply composite laminate joint structure comprising a first ply of tensioned and compacted unidirectional continuous first filament strands 2 disposed upon an impeL-meable plastic liner and collimat:ed to have a direction approximately parallel to the laminate joint end terminator and the joint flange face configured by filament strands 3 and arranged to form at the join~t end a tapc-red second ply support sul-face having an angle of taper approximately equal to 8.
A second ply of tensioned and compacted unidirectional continuous second filament str.ands 1 having a uniform thickness ~as ~isposed transversely of and superimposed upon the first filament strands to form the tapered-end second ply support surface. A third ply of tensioned ~ZZ97~3 and compacted unidirectional continuous third filament strands 3 disposed transversely of and superimposed upon the second filament strands was confiyured to have a joint flange on the tapered end of said second ply and a joint flange face parallel to the terminator of the composite laminate joint structure.
The impermeable plastic liner was made of a thermosetting vinylester resin reinforced with a non-woven fabric comprised o~ glass fiber. The continuous filarnent strands comprising the first, second and third laminate plies consisted of glass roving strands each of which has a "yield" of 225 yards per pound, a dry strand breaking strength in excess of 200 pounds, a strand filament count of 2000 having individual filament diameters ranging from 0.00090 to 0.00095 inch. The resin matrix material used to impregnate the continuous filament strands was a liquid thermosetting polyester resin.
The total thickness of the non-tapered portion of the exampled multiple ply compOsite structure depicted in FIG. 4 was approximately 0.34 inch in which the plastic liner was approximately 0.09 inch, the first ply thickness was 0.06 inch, and the third ply thickness was 0.12 inch. The flanged face configured from the third ply filament strands, 3, was approximately 0.25 inches high and positioned approximately 3 inches from the tapered end termina-tor face of the composite laminate joint structure The above described joint structure was able to resist an end load in excess of 7200 pounds per inch of joint structure width.

Example 2 FIG. 5 illustrates a partially sectioned side elevation view of an assembly of tubular composite laminate joint structures used to mechanically join and seal pressure pipe which was tested to demollstrate that the pipe and coupling meets or exceeds: (a) the performance requirements for water pipe established 1~297B;~

by American ~-'ater l~orks Association (A~ A) and the American ~Jational Standards Institute (ANSI) in the AWWA Standard ANSI/A~'WA C950-81, (b) the specification requirements for line pipe, casing and tubing established by American Petroleum Institute in API
Spec SLR and API Spec 5Ar, and (c) the design and test criteria for pressure piping established by the American Society of Mechanical Engineers in ASME Code B31.3 and B31.q.
The pressure pipe joint detail depicted in FIG 5 depicts a means of connecting two lengths of filament wound composite Reinforced Thermosetting Resin Pipe (RTRP), cach length of which have iden~ical pipe joint ends 10, sealed by a pair of rubber "O"
rings 9 positioned on a 4 inch long reinforced plastic tubular seal sleeve structure 8 having a wall thickness of approximately 0.31 inches and an inner diameter equal to that of the pipe joint ends 10 Each joint end of the composite filament wound pipe comprised an inner impermeable liner 4 approximately 0.1 inch thick made of a glass fiber reinforced thermosetting vinylester resin which extended the full length of the pipe and which served as the sealing surface against which each rubber "O" ring seal 9 was compressed.
A first ply of continuous CIRC filament strands 2 was filament wound upon the liner structure 4 of each pipe to a minimum wall thickness of approxi-mately 0.06 inches and enlarged at each pipe end to provide a conical laminate ply support s~rface having an angle of approximately 8 with respect to the pipe longitudinal axis.
A second ply comprising continuous LO~GO
filament strands 1 was transversely disposed upon the first ply CIRC filament strands to provide a LO~'GO ply laminate having a uniform thickness of approximately 0.09 inches and flared at the pipe ends ~X297~
at a taper angle approximately equal to that of the first ply joint structure. The across strand shear path of the resulting flared LONGO ply laminate was calculated to equal 0.65 inches or approximately seven times the LONGO ply laminate thickness thereby enabling a joint tenslle load at least equal to 5000 pounds per inch of pipe circumference to be resisted by the continuous longitudinally directed filament strands cornprising the second ply laminate.
0 A third ply comprising continuous CIRC
filament strands 3 was filament wound upon the second ply LONGO strands to tension and compress the LONGO filament strands against the first ply tubular structure. The filament wound thickness of the third ply laminate was approximately 0.12 except for the pipe joint ends where the third ply filament strands 3 were configured to form a 3 inch wide cylindrically shaped flange having a load bearing annular plane surface extending approximately 0.25 inches above the pipe outer wall surface.
After the pipe ends were mated with the seal sleeve structure 8 the two piece segmented composite coupling structure 7 was positioned to engage and secure the abutting flanges of each pipe end. The segmented coupling structure 7 shown in FIG. 5 in a partially sectioned side elevation view comprises a first ply of continuous filzment CIRC strands 2s filament wound upon a removable segmented coupling forming structure and configured at each end to have a tapered laminate support surface having a taper angle a of approximately 15. A
second ply of continuous filament LONGO strands 1s was then transversely disposed upon the segrnented coupler first ply filament strands. A third ply of continuous filament strands 3s was afterwards filament wound upon the segmented coupler second ply LONGO
strands to simultaneously tension and compress the ~297~3 LONGO filament strands against the segmented coupler first ply support structure. A sufficient thickness of third ply filament strands was filament wound upon the segmented coupler second ply filament strands to provide a cylindrically shaped segmented coupllng structure having a uniform outer surface diameter.
The outer surface of the two piece segrnented coupling structure 7 was then covered with a resin impregnated woven fabric comprised of filament reinforcements to provide an improved structural integrity to the segmented coupling structure.
After the two piece coupling structure was positioned to engage the pair of pipe end flanges, a cylindrical filament wound tubular lock sleeve 6 having an inner diameter slightly larger that the outer diameter of the segmented coupling structure was slipped over the coupling halves to secure and lock the segmented coupling structure in a position that enabled the coupling structure to resist the tensile forces applied to the pipe joint structure.

Example III

FIG. 6 is an exploded view of a composite pipe joint and segmented coupling structure similar to that illustrated in FIG. 5 except that the exterior third ply flange structure 3 of each pipe joint end is configured to have an annular groove to retain an "O" ring seal 9 and the sealing sleeve structure 8 has an inner bore diameter designed to compress the pair of rubber "O" rings to provide a satisfactory pressure seal. Each of the tubular multiple ply composite laminate structures 10 were constructed in a manner similar to that illustrated in FIG. 4 inasmuch as the first plyilaminate support structure w,asnOt recessed to accept a sealing sleeve. The two piece seqmented coupling 7 illustrated in FIG. 6 is similar to that illustrated in FIG. S except it has a larger outer diameter to enable it to accomodate a sealing sleeve, 8, positioned upon the pipe joint 12:~97~,3 flanges comprised of filament wo~nd third ply continuous filament CIRC strands 3. The lock sleeve 6 shown in FIG. 6 was also required to have a larger diameter for a given pipe size than the lock sleeve shown in FIG. 5 and was provided with a pair of threaded lock bolts 11 to prevent the lock sleeve from being moved.

Claims

Claims:

1. An apparatus for forming a composite laminate joint structure thereon comprising a mandrel comprising separate parts releasably attached together in axial alignment by fastening means, said mandrel mounted on a longitudinal axis thereof and having an annular cross section throughout its length, at least one pair of annular filament strand gripping means spaced apart longitudinally on the perifery of one of the parts of said mandrel, each of said gripping means extending radially outwardly from said axis and terminating at a convex surface, the radial heights of said gripping means being sufficient to enable longitudinally disposed filament strands attached to said gripping means to be formed into a composite laminate having a tapered end configuration, at least one removable annular flange forming means adapted to be positioned adjacent to the inward angle-forming edge of a tapered laminate comprising an end portion of a multiple ply composite laminate structure formed upon said mandrel.