CN101786324A - Method for accurately designing molded surface of autoclave forming fixture for composite products - Google Patents

Abstract

The invention relates to a method for accurately designing the molded surface of an autoclave forming fixture for composite products, belonging to the technical field of autoclave forming fixture design for composite products. The method utilizes a cooling curve of a product curing technology curve, disperses a product molded surface S into a plurality of points at room temperature and calculates a product molded surface S' at the stress critical temperature by the displacement formula of the points according to the thermal expansion coefficient of the products. When a fixture molded surface G' is the same with the product molded surface at the stress critical temperature, S' is equal to G'. And a fixture molded surface G at room temperature is calculated according to the fixture molded surface G' and the thermal expansion coefficient of a fixture material. The method solves the problem that the traditional design method generates the fixture molded surface by directly copying the product room temperature molded surface and repairs dies repeatedly according to the rebound, reduces the development and production costs and improves the design efficiency and quality.

Description

Method for accurately designing molded surface of autoclave forming fixture for composite products

Technical field

The present invention relates to a kind of method for accurately designing molded surface of autoclave forming fixture for composite products, belong to composite product autoclave shaping frock design field.

Background technology

Autoclave shaping frock is the basis that the advanced composite material product is shaped, and it plays the effect of transmitting temperature and pressure, location and assurance molding surface size precision.What need the emphasis consideration in the frock design is the design of frock profile, and this plays a part very important to composite product forming accuracy and quality.

Composite product is after experience hot setting and cooling procedure because the complex effects factors such as chemical reaction blockage effect of the expand with heat and contract with cold effect and the matrix resin of material, can generation between its profile and the theoretical profile to a certain degree inconsistent.This distortion of composite product produces totally unfavorable influence to the precision and the coupling of the connection between the product of product profile.In order to overcome above problem, traditional method for designing is directly to extract the profile of product under the normal temperature, the profile of on the basis of design experiences and technology experience the curing process standard and the product of product being solidified used frock is carried out adjustment and compensatory correction processing repeatedly, with the control deformation extent or offset the influence of distortion.Easily deform in manufacturing, when having the composite product of strict type surface accuracy requirement again simultaneously, the exemplary operation program is:

Step 1: the design profile copy according to product generates the tool mold profile;

Step 2: the frock manufacturing process testpieces of step manufacturing in the utilization;

Step 3: according to the deflection correction tool mold profile of engineer testing part;

Step 4: go on foot revised frock manufacturing process testpieces once more in the utilization;

Step 5: repeating step 3,4, until meeting the demands.

Adopt the method that the part profile is carried out the frock design of directly extracting, the dimensional accuracy of the composite product of shaping is low, and product profile precision can not get guaranteeing; For improving the precision of frock shaping product, need experience repeatedly trial and error and repair a die, the development cost height, the cycle is long.

Summary of the invention

The present invention is a composite product autoclave shaping tool mold profile method for accurately designing.This method has solved traditional design and has directly copied generation tool mold profile by product room temperature profile, and the problem that repairs a die repeatedly according to resilience has reduced development cost then, has improved design efficiency and quality.

Design of the present invention:

The first step: thermosetting resin will experience four kinds of states from mechanical property and physical state analysis in solidification process: the glassy state behind the glassy state of gel, viscous state, elastomeric state and the gel not; Before elastomeric state, to elastomeric state, fit fully by composite product and frock profile by liquid state for composite product, and the composite product profile becomes with the frock profile, and is unstressed between the two; Along with solidification process carries out, when reaching the stress critical point, frock profile decision product profile, after the stress critical point, expanding with heat and contract with cold physically mainly takes place in composite product.

If the product profile is S under the room temperature, product profile S ' under the critical-temperature, the product thermal coefficient of expansion is by α _IAnd α _TForm, wherein α _IThe thermal coefficient of expansion on plane, α _TThermal coefficient of expansion on the thickness direction; For thin-walled class composite product, only consider the thermal expansion in the plane.The frock profile is G under the room temperature, frock profile G ' under the stress critical point temperature.For the composite frock, thermal coefficient of expansion is by α _1IAnd α _1TForm, for the metal frock, thermal coefficient of expansion is α ₁By known product curing process curve, determine the stress critical point temperature.

Second step: be separated into a plurality of points by product profile S under the room temperature, utilize the displacement formula of point and the thermal coefficient of expansion of product, product profile S ' under the calculated stress critical point temperature;

The 3rd step: frock profile G ' is identical with the product profile under the stress critical point temperature, i.e. S '=G ';

The 4th step: according to frock profile under the stress critical point temperature is G ' and frock material coefficient of thermal expansion coefficient, calculates frock profile G under the room temperature.

The present invention proposes composite product first in the autoclave forming process, under the solidification temperature, has the critical point that begins to produce stress between a frock and the product profile.During the stress critical point, frock profile and composite product profile are fitted fully, and accurately determine the profile of product.After the stress critical point, the process of expansion and contraction on the physical significance mainly takes place in the distortion of composite product.Along the temperature lowering curve of product process curve, product is reversible from distortion and the temperature-fall period that room temperature rises to the stress critical point temperature.

The accurate design considerations of frock profile is proposed first.According to the temperature lowering curve in the product curing process curve, be separated into a plurality of points by product profile S under the room temperature, according to the thermal coefficient of expansion of product, utilize the displacement formula of point, product profile S ' under the calculated stress critical point temperature.Frock profile G ' is identical with the product profile under the stress critical point temperature, i.e. S '=G '.According to frock profile G ' and frock material thermal expansion coefficient, calculate frock profile G under the room temperature, and be the accurate design considerations of frock profile with G.

The present invention is a kind of composite autoclave shaping tool mold profile method for accurately designing, use this method for designing, on the one hand, it is low that the elimination conventional method is directly extracted the composite product profile design part accuracy that frock caused, a difficult problem that needs repeatedly trial and error to repair a die; On the other hand, composite product deformation effect factors such as complicated chemistry, physical change in solidification process have been avoided considering.Method for designing of the present invention under the prerequisite that guarantees precision, has improved designing quality and efficient.

Description of drawings

Fig. 1 technology path of the present invention.

Fig. 2 is shaped as the change in size schematic diagram of the composite product of curved surface.

The definition schematic diagram of Fig. 3 angle beta.Schematic diagram when wherein Fig. 3-1 is positive angle; Schematic diagram when Fig. 3-2 is negative angle.

Fig. 4 curve OA change in location schematic diagram.

Fig. 5 curve B C change in location schematic diagram.

The schematic diagram of Fig. 6 straight line AB change in location.

The change in location schematic diagram of discrete point on Fig. 7 curve.

The number in the figure title:

Among Fig. 2: OABC is the curve in the original curved surface, and O ' A ' B ' C ' is the curve after changing.

Among Fig. 3: the definition of angle beta, wherein, τ _i, τ _I-1Be respectively a P _i, P _I-1The angle of place's tangential direction.

Among Fig. 4: among the coordinate system oxy, angle φ _OAAnd φ ^/ _OABe respectively an A and A ' and locate the supplementary angle of tangential direction angle, angle χ _OABe local coordinate system o ξ ₁η ₁Down, the angle of curve OA distortion.

Among Fig. 5: Δ φ _OAThe changing value of straight line two actors playing the same role in a theatrical work degree.

Among Fig. 6: angle χ _BCFor curve B C at local coordinate system o ξ ₂η ₂Under angle change.

Among Fig. 7: the state diagram of some P change in location.

The specific embodiment

A kind of composite autoclave shaping frock profile method for accurately designing is applicable under the known precondition of the thermal coefficient of expansion of curing process curve, product and frock of autoclave formed composite material product and carries out, and it is characterized in that concrete grammar is as follows:

The first step: thermosetting resin will experience four kinds of states from mechanical property and physical state analysis in solidification process: the glassy state behind the glassy state of gel, viscous state, elastomeric state and the gel not; Before elastomeric state, to elastomeric state, fit fully by composite product and frock profile by liquid state for composite product, and the composite product profile becomes with the frock profile, and is unstressed between the two; Along with solidification process carries out, when reaching the stress critical point, frock profile decision product profile, after the stress critical point, expanding with heat and contract with cold physically mainly takes place in composite product.By known product curing process curve, determine the stress critical point temperature;

Second step: be separated into a plurality of points by product profile S under the room temperature, utilize the displacement formula of point and the thermal coefficient of expansion of product, product profile S ' under the calculated stress critical point temperature;

The 3rd step: frock profile G ' is identical with the product profile under the stress critical point temperature, i.e. S '=G ';

The 4th step: according to frock profile under the stress critical point temperature is G ' and frock material thermal expansion coefficient, calculates frock profile G under the room temperature.

Temperature-rise period from room temperature to the stress critical point temperature, the product profile calculation procedure under the stress critical point temperature is as follows:

The first step: set up original coordinate system oxy

Suppose that composite product is general curve form, curved surface can be generated by the control curve.Curve two-dimensional shapes OABC curve as shown in Figure 2, wherein OA, BC are curve, AB is a straight line.The A point coordinates is A=[x _A, y _A, 1] ^T, B ' point coordinates is B=[x _B, y _B, 1] ^T, C ' point coordinates is C=[x _C, y _C, 1] ^TThe angle of curve OA is φ _OA, radius is r _OAThe angle of curve B C is φ _BC, radius is r _BCBe warmed up to the stress critical point temperature, some A, B, C move to A ' respectively, B ', C ', as shown in Figure 2.

In order to narrate conveniently, introduce angle beta, be the angle changing value before and after the product expansion.As shown in Figure 3.Wherein: P _I-1Be the starting point that changes, P _iBe the terminal point that changes.β just is being deflected to counterclockwise, as left figure; Be deflected to clockwise negative, as Fig. 3.

β is expressed as:

β _i＝τ _i-τ _i-1 (1)

Wherein:

${\mathrm{\τ}}_i=\arctan \⟨\frac{\mathrm{dy}}{\mathrm{dx}}{|}_{P_i}\⟩,$ ${\mathrm{\τ}}_{i-1}=\arctan \⟨\frac{\mathrm{dy}}{\mathrm{dx}}{|}_{P_{i-1}}\⟩---\left(2\right)$

Product is because heat expansion causes that the variation of angle can be expressed as:

$\mathrm{\Δ\φ}=\frac{{\∫}_{T_0}^{T_C}({\mathrm{\α}}_T-{\mathrm{\α}}_I)\mathrm{dT}}{1+{\∫}_{T_0}^{T_C}{\mathrm{\α}}_T\mathrm{dT}}\mathrm{\β}---\left(3\right)$

In the formula: α _IThe thermal coefficient of expansion on plane; α _TThermal coefficient of expansion on the thickness direction; T ₀Be room temperature; T _CBe the stress critical point temperature.

Second step:

Analyze the OA curve deformation, set up local coordinate system o ξ ₁η ₁As shown in Figure 4:

Angle χ _OABe defined as ${\mathrm{\χ}}_{\mathrm{OA}}=\arctan \left(\frac{y_A-y_O}{x_A-x_O}\right),$

The length of OA is: $\left|\mathrm{OA}\right|=\sqrt{{(x_A-x_O)}^2+{(y_A-y_O)}^2},$ Since the expansion of product on thickness direction, r _OAIncrease is:

$r_{\mathrm{OA}}^{/}=\frac{(1+{\mathrm{\α}}_T\mathrm{\ΔT})\sqrt{{(x_A-x_O)}^2+{(y_A-y_O)}^2}}{2\left|\sin \left(\frac{{\mathrm{\β}}_{\mathrm{OA}}}{2}\right)\right|}---\left(4\right)$

Therefore, coordinate system o ξ ₁η ₁In, A ' coordinate is:

${\mathrm{\ξ}}_A=\frac{(1+{\mathrm{\α}}_T\mathrm{\ΔT})\sqrt{{(x_A-x_O)}^2+{(y_A-y_O)}^2}\sin \left(\frac{{\mathrm{\β}}_{\mathrm{OA}}-\mathrm{\Δ}{\mathrm{\Φ}}_{\mathrm{OA}}}{2}\right)\cos \left(\frac{\mathrm{\Δ}{\mathrm{\Φ}}_{\mathrm{OA}}}{2}\right)}{\sin \left(\frac{{\mathrm{\β}}_{\mathrm{OA}}}{2}\right)}$

${\mathrm{\η}}_A=\frac{(1+{\mathrm{\α}}_T\mathrm{\ΔT})\sqrt{{(x_A-x_O)}^2+{(y_A-y_O)}^2}\sin \left(\frac{{\mathrm{\β}}_{\mathrm{OA}}-\mathrm{\Δ}{\mathrm{\Φ}}_{\mathrm{OA}}}{2}\right)\sin \left(\frac{\mathrm{\Δ}{\mathrm{\Φ}}_{\mathrm{OA}}}{2}\right)}{\sin \left(\frac{{\mathrm{\β}}_{\mathrm{OA}}}{2}\right)}---\left(5\right)$

In the oxy coordinate system, the coordinate of A ' is:

$x_A^{/}={\mathrm{\ξ}}_A\cos {\mathrm{\χ}}_{\mathrm{OA}}-{\mathrm{\η}}_A\sin {\mathrm{\χ}}_{\mathrm{OA}}---\left(6\right)$

$y_A^{/}={\mathrm{\ξ}}_A\sin {\mathrm{\χ}}_{\mathrm{OA}}-{\mathrm{\η}}_A\cos {\mathrm{\χ}}_{\mathrm{OA}}$

With formula (5) substitution formula (6), etc.:

$x_A^{/}=\frac{(1+{\mathrm{\α}}_T\mathrm{\ΔT})\sqrt{{(x_A-x_O)}^2+{(y_A-y_O)}^2}\sin \left(\frac{{\mathrm{\β}}_{\mathrm{OA}}-\mathrm{\Δ}{\mathrm{\Φ}}_{\mathrm{OA}}}{2}\right)\cos (\frac{\mathrm{\Δ}{\mathrm{\Φ}}_{\mathrm{OA}}}{2}+{\mathrm{\χ}}_{\mathrm{OA}})}{\sin \left(\frac{{\mathrm{\β}}_{\mathrm{OA}}}{2}\right)}---\left(7\right)$

$y_A^{/}=\frac{(1+{\mathrm{\α}}_T\mathrm{\ΔT})\sqrt{{(x_A-x_O)}^2+{(y_A-y_O)}^2}\sin \left(\frac{{\mathrm{\β}}_{\mathrm{OA}}-\mathrm{\Δ}{\mathrm{\Φ}}_{\mathrm{OA}}}{2}\right)\sin (\frac{\mathrm{\Δ}{\mathrm{\Φ}}_{\mathrm{OA}}}{2}+{\mathrm{\χ}}_{\mathrm{OA}})}{\sin \left(\frac{{\mathrm{\β}}_{\mathrm{OA}}}{2}\right)}$

The 3rd step:

For straightway AB, set up coordinate system ox ₁y ₁, scheme shown in Figure 5.The coordinate of point B ' is:

$x_{\mathrm{BA}}^{/}=(1+{\mathrm{\α}}_I\mathrm{\ΔT})x_{\mathrm{BA}}---\left(8\right)$

$y_{\mathrm{BA}}^{/}=(1+{\mathrm{\α}}_I\mathrm{\ΔT})y_{\mathrm{BA}}$

Because the expansion Δ φ that curve OA causes _OA, the coordinate of some B ' in coordinate system oxy is:

$x_B^{/}=x_A^{/}+x_{\mathrm{BA}}^{/}\cos \mathrm{\Δ}{\mathrm{\φ}}_{\mathrm{OA}}-y_{\mathrm{BA}}^{/}\sin \mathrm{\Δ}{\mathrm{\φ}}_{\mathrm{OA}}---\left(9\right)$

$y_B^{/}=y_A^{/}+x_{\mathrm{BA}}^{/}\sin \mathrm{\Δ}{\mathrm{\φ}}_{\mathrm{OA}}-y_{\mathrm{BA}}^{/}\cos \mathrm{\Δ}{\mathrm{\φ}}_{\mathrm{OA}}$

The 4th step:

For curve B C section, set up local coordinate system o ξ ₂η ₂, as Fig. 6:

Point C ' is at coordinate system o ξ ₂η ₂In coordinate be:

$x_{\mathrm{CB}}^{/}=\frac{(1+{\mathrm{\α}}_T\mathrm{\ΔT})\sqrt{{(x_C-x_B)}^2+{(y_C-y_B)}^2}\sin \left(\frac{{\mathrm{\β}}_{\mathrm{BC}}-\mathrm{\Δ}{\mathrm{\Φ}}_{\mathrm{BC}}}{2}\right)\cos (\frac{\mathrm{\Δ}{\mathrm{\Φ}}_{\mathrm{BC}}}{2}+{\mathrm{\χ}}_{\mathrm{BC}})}{\sin \left(\frac{{\mathrm{\β}}_{\mathrm{BC}}}{2}\right)}---\left(10\right)$

$y_{\mathrm{CB}}^{/}=\frac{(1+{\mathrm{\α}}_T\mathrm{\ΔT})\sqrt{{(x_C-x_B)}^2+{(y_C-y_B)}^2}\sin \left(\frac{{\mathrm{\β}}_{\mathrm{BC}}-\mathrm{\Δ}{\mathrm{\Φ}}_{\mathrm{BC}}}{2}\right)\sin (\frac{\mathrm{\Δ}{\mathrm{\Φ}}_{\mathrm{BC}}}{2}+{\mathrm{\χ}}_{\mathrm{BC}})}{\sin \left(\frac{{\mathrm{\β}}_{\mathrm{BC}}}{2}\right)}$

Point C ' at the coordinate of coordinate system oxy is:

$x_C^{/}=x_B^{/}+x_{\mathrm{CB}}^{/}\cos ({\mathrm{\Δ\φ}}_{\mathrm{OA}}+\mathrm{\Δ}{\mathrm{\φ}}_{\mathrm{AB}})-y_{\mathrm{CB}}^{/}\sin (\mathrm{\Δ}{\mathrm{\φ}}_{\mathrm{OA}}+\mathrm{\Δ}{\mathrm{\φ}}_{\mathrm{AB}})---\left(11\right)$

$y_C^{/}=y_B^{/}+x_{\mathrm{CB}}^{/}\sin ({\mathrm{\Δ\φ}}_{\mathrm{OA}}+\mathrm{\Δ}{\mathrm{\φ}}_{\mathrm{AB}})-y_{\mathrm{BA}}^{/}\cos (\mathrm{\Δ}{\mathrm{\φ}}_{\mathrm{OA}}+\mathrm{\Δ}{\mathrm{\φ}}_{\mathrm{AB}})$

By above analysis as can be known, for the analysis of general surf deform, at first set up coordinate system oxy, in coordinate system oxy the curve segmentation of his-and-hers watches curved surface is become n curve then, node is P ₀, P ₁, P ₂P _N-1, P _n, calculating the contraction and the heat expansion of each section respectively, Fig. 7 is seen in the variation of the position of any point signal on the curved surface.

The change in location of point P can be represented by the formula:

$P_n^{/}={\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="HSA00000028972700031.png"\; state="\{\{state\}\}">P</figure-callout>}}_0+{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="HSA00000028972700031.png"\; state="\{\{state\}\}">P</figure-callout>}}_0^{/}{P}_1^{/}+\underset{i=2}{\overset{n}{\mathrm{\&Sigma;}}}\left[\left(\underset{j=1}{\overset{i-1}{\mathrm{\&Pi;}}}{R}_{\mathrm{zj}}\right)P_{i-1}^{/}{P}_i^{/}\right]---\left(12\right)$

P _iP _I-1Some P in the expression local coordinate system _iWith respect to P in original coordinate system _I-1Coordinate.

Curve table is shown:

$P_{i-1}^{/}{P}_i^{/}=\left[\begin{array}{c}\frac{(1+{\mathrm{\&alpha;}}_T\mathrm{\&Delta;T})\left|P_{i-1}{P}_i\right|\sin \left(\frac{{\mathrm{\&beta;}}_i-\mathrm{\&Delta;}{\mathrm{\&Phi;}}_i}{2}\right)\mathrm{coc}(\frac{\mathrm{\&Delta;}{\mathrm{\&Phi;}}_i}{2}+{\mathrm{\&chi;}}_i)}{\sin \left[\frac{{\mathrm{\&beta;}}_i}{2}\right]}\\ \frac{(1+{\mathrm{\&alpha;}}_T\mathrm{\&Delta;T})\left|P_{i-1}{P}_i\right|\sin \left(\frac{{\mathrm{\&beta;}}_i-\mathrm{\&Delta;}{\mathrm{\&Phi;}}_i}{2}\right)\sin (\frac{\mathrm{\&Delta;}{\mathrm{\&Phi;}}_i}{2}+{\mathrm{\&chi;}}_i)}{\sin \left[\frac{{\mathrm{\&beta;}}_i}{2}\right]}\end{array}\right]---\left(13\right)$

Straight line is expressed as:

$P_{i-1}^{/}{P}_i^{/}=(1+{\mathrm{\&alpha;}}_I\mathrm{\&Delta;T})P_{i-1}{P}_i---\left(14\right)$

Change in size is expressed as:

$\mathrm{\&delta;}{P}_n={\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="HSA00000028972700031.png"\; state="\{\{state\}\}">P</figure-callout>}}_0+{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="HSA00000028972700031.png"\; state="\{\{state\}\}">P</figure-callout>}}_0^{/}{P}_1^{/}+\underset{i=2}{\overset{n}{\mathrm{\&Sigma;}}}\left[\left(\underset{j=1}{\overset{i-1}{\mathrm{\&Pi;}}}{R}_{\mathrm{zj}}\right)P_{i-1}^{/}{P}_i^{/}\right]-P_n---\left(15\right)$

From above analysis as can be known, utilize the thermal coefficient of expansion on all directions of composite product, calculate the change in location of each point, the position of the back profile point of can accurately determining to expand fits to curved surface at last a little.

The temperature-fall period that rises from the stress critical point temperature to room temperature, frock profile calculation of Deformation process and product profile elevated temperature deformation compute classes are seemingly.As frock is composite, then makes α _I=α _1I, α _T=α _1T, be metal material as frock, then make α _I=α _T=α ₁

Claims (1)

1. the autoclave shaping frock profile method for accurately designing of a composite product is characterized in that design procedure is as follows:

The first step: thermosetting resin will experience four kinds of states from mechanical property and physical state analysis in solidification process: the glassy state behind the glassy state of gel, viscous state, elastomeric state and the gel not.Before elastomeric state, to elastomeric state, fit fully by composite product and frock profile by liquid state for composite product, and the composite product profile becomes with the frock profile, and is unstressed between the two.Along with solidification process carries out, when reaching the stress critical point, frock profile decision product profile, after the stress critical point, expanding with heat and contract with cold physically mainly takes place in composite product.If the product profile is S under the room temperature, product profile S ' under the stress critical point temperature, the frock profile is G under the room temperature, frock profile G ' under the temperature of stress critical point by known product curing process curve, determines the stress critical point temperature;

Second step: be separated into a plurality of points by product profile S under the room temperature,, utilize the displacement formula of point, product profile S ' under the calculated stress critical point temperature according to the product thermal coefficient of expansion;

The 3rd step: frock profile G ' is identical with the product profile under the stress critical point temperature, i.e. S '=G ';

The 4th step: according to frock profile under the stress critical point temperature is G ' and frock material thermal expansion coefficient, calculates frock profile G under the room temperature.

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