CN106599507A - Hierarchical prediction method for composite material multi-direction lamination board by considering fiber bridge connection influence based on improved B-K criterion - Google Patents

Abstract

The invention discloses a hierarchical prediction method for a composite material multi-direction lamination board by considering fiber bridge connection influence based on improved B-K criterion. By performing a static force hierarchical test on I type, II type and I/II mixed type of different mixed ratios of CFRP multi-direction lamination board, I type interlayer fracture toughness GIC (a), II type interlayer fracture toughness GIIC (a) and interlayer fracture toughness GC (a) of different mixed ratios which are changed along with hierarchical lengths are determined; least square fitting on three-dimensional data is performed to obtain a parameter <eta> in the improved B-K criterion considering the fiber bridge connection influence; next, by taking the GIC (a), the GIIC (a) and the fitting parameter <eta> as important parameters in the improved B-K criterion, a finite element model based on a cohesion unit is established, and hierarchical expansion behaviors of different mixed ratios are simulated by applying the improved criterion; and the accuracy and the applicability of the disclosed improved criterion are verified by contrast tests and numerical value results, so that hierarchical expansion behaviors of any other mixed ratios can be further predicted by applying the improved criterion, thereby greatly shortening the experimental period and lowering experimental cost.

Description

One kind improves B-K criterions is used for the multidirectional laminate point of fibre-bearing bridge joint impact composite The method of layer prediction

Technical field

The present invention relates to CFRP multi direction laminate delaminations field, and in particular to one kind improves B-K criterions to be used for containing fibre The method that dimension bridge joint affects the multidirectional Laminates With Delamination prediction of composite, it is adaptable to the widely used composite wood in the field such as Aero-Space Expect the research and prediction of multidirectional laying plate I/II Mixed-Mode Delamination propagation behaviors.

Background technology

Composite is gradually applied in aircraft main force support structure because of its good mechanical property.Wherein, carbon fiber tree Resin-based composite has specific stiffness height concurrently while with compared with high specific strength, and anticorrosive, fatigue behaviour is good and performance can set Meter property many advantages, such as and become a kind of composite mainly used in Modern aircraft structure.With middle modulus high strength carbon fibre The batch production of dimension and the application of toughened resin, application of this kind of composite in aircaft configuration also by secondary load-carrying construction gradually Develop into the complicated main force support structure of force-bearing situation.And the safety of structure of composite is also increasingly valued by the people.

In the numerous failure modes of laminar composite, come off by low velocity impact, synusia, recess or manufacturing defect cause Layering is one of most common and crucial failure mode.Delamination damage causes veneer structure strength and stiffness to be remarkably decreased, or even The calamitous structure destruction that outside is difficult to discover is likely to result in, this seriously constrains composite answering in aircraft main structure With.Therefore it is correct to evaluate and predict that composite is multiple in various load and environmental condition lower leaf propagation behavior are to engineering practice The design and analysis of condensation material structure is extremely important, while also can significantly shorten the test period, reduces experimentation cost.

Cohesive zone model (CZM) is widely used to simulate the germinating and extension of layering.Cohesive zone model releases strain energy Rate (SERR) and interlayer faults toughness are put as the standard of assessment delamination, prediction I/II Mixed-Mode Delamination extensions most extensively make Criterion is B-K criterions.In traditional B-K criterions, I types and II type interlayer faults toughness be assumed to be with specimen size and point The unrelated intrinsic parameter of material of layer length, this hypothesis is correct for unidirectional laminate, but for multi direction laminate shows Unworthiness is shown.Traditional B-K criterions of the judge delamination in bilinearity CZM, due to not considering the impact that fiber is bridged, Cannot accurate simulation multi direction laminate delamination behavior.

During delamination in the multidirectional laying plate of composite, fiber bridge joint is a kind of very important crackle screen Cover mechanism.Research shows that the quantity of moderate loss actually depends on layering length, it means that compared with short crack, long crack In will appear from more moderate loss, it is therefore desirable to the fracture for consuming more energy to make FRP rebar or cause moderate loss Failure.Can be seen that fiber bridge joint significantly suppress multidirectional laying from the fracture toughness change curve of multidirectional laying plate delamination The delamination of plate, it is therefore desirable to consider the impact of fiber bridge joint in delamination.Consider that the improvement B-K that fiber bridge joint affects is accurate Then, multidirectional laying plate Mixed-Mode Delamination propagation behavior can be just better anticipated.

The content of the invention

The technical problem to be solved in the present invention is：Overcome the deficiencies in the prior art, there is provided one kind improves B-K criterions to be used to contain The method that fiber bridge joint affects the multidirectional Laminates With Delamination prediction of composite, it is adaptable to engineer applied, significantly shortens test period, drops Low experimentation cost.Any mixing ratio lower leaf propagation behavior of the multidirectional laying plate of composite is carried out simultaneously effectively analyzing and pre- Survey, preferably ensure safety of structure.

The present invention solve the technical scheme that adopts of above-mentioned technical problem for：One kind improves B-K criterions for fibre-bearing bridge joint The method for affecting the multidirectional Laminates With Delamination prediction of composite, comprises the following steps：

Step 1, by double cantilever beam bending (DCB), 4 end edge otch (4ENF) and Mixed Bending (MMB) experiment opening I types, II types and the test of I/II mixed type static(al)s delamination of the multidirectional laminates of CFRP are opened up, corresponding load, displacement is obtained and is split The test datas such as line length；

Step 2, data processing is carried out to test data and determines I type interlayer faults toughness G changed with layering length a_IC (a), II type interlayer faults toughness G_IICMixed type interlayer faults toughness G under (a) and different mixing ratios_C(a)；

Step 3, step 2 is obtained G using the improvement B-K criterions of fiber bridge joint in consideration delamination_IC(a)、G_IIC G under (a) and different mixing ratios_CA () carries out the least square fitting of three-dimensional data, so that it is determined that many suitable for studying CRFP Parameter η value in the improvement B-K criterions of laminate；

Step 4, sets up based on the FEM model of cohesive force unit, by User Defined subprogram USDFLD, will be upper State CFRP multi direction laminate I types and II type interlayer faults toughness G_IC(a)、G_IICPass through a most young waiter in a wineshop or an inn in the expression formula of (a) and step 3 The parameter η value in the improvement B-K criterions that fitting obtains is taken advantage of to be embedded in improvement B-K criterions, using the improvement as important parameter B-K criterions simulate the delamination behavior under this kind of multi direction laminate difference mixing ratio, and by contrast test and numerical result The accuracy for improving B-K criterions is set up to verify.

Further, it is (+45/-45/0 that checking improves CFRP multi direction laminates ply stacking-sequence used by criterion₆)_S//(-45/+ 45/0₆)_S, the design of this kind of ply stacking-sequence is the mutual recurvation in order to reduce bending-torsional coupling effect and cause because laying is asymmetric Qu Xiaoying.

Further, the ply stacking-sequence is (+45/-45/0₆)_S//(-45/+45/0₆)_SCFRP multi direction laminates be Made using the unidirectional pre-immersion material of T7009511 carbon fibers/bismaleimide resin system.

Further, the step 2 determines the I type interlayer faults toughness with layering length a change using amendment beam theory G_ICA () expression formula is：

Wherein：B is specimen width, and F and N' is respectively modifying factor when considering that big displacement and loading blocks affect, due to surveying Amount is to be layered the sophisticated vertical range away from loaded line and employ hinge rather than loading blocks, and the two factors are 1.P_ICWith δ_ICIt is respectively the I types load and displacement that sample is applied, | △ | is the modifying factor for being layered length, for considering that cantilever is splitting point The position displacement additional due to material anisotropy and rotation.

The step 2 determines II type interlayer faults toughness G with layering length a change using flexibility method_IIC(a) expression formula For：

Wherein：P_CIt is critical load, C is sample flexibility.

The step 2 determines I/II mixed type interlayer faults toughness G with layering length a change according to amendment beam theory_C A () expression formula is：

G_C(a)=G_I(a)+G_II(a)

Wherein：P is the load applied at the point of application, and c is the point of application to the middle distance for loading roller bearing, P_gBe entablature and It is attached to the weight of wherein loading blocks, c_gCenter of gravity for fixture loads the distance of roller bearing, E to centre_fIt is bending modulus, h is that sample is thick That what is spent is general, and L is fixed span away from as shown in accompanying drawing 3 (c).

Further, above-mentioned I types are fitted in the step 3 respectively, II type delamination test datas are obtained with layering The G of length change_IC(a)、G_IICThe mathematic(al) representation of (a), the G of the CFRP multi direction laminates_ICA () expression formula is segmentation letter Number, is divided into fiber bridge joint sections and stablizes expanding section；The G of the CFRP multi direction laminates_IICA () expression formula passes through linear fit Obtain.

Further, it is based in the step 3 and improves B-K criterions to above-mentioned gained delamination fracture toughness data G_IC (a)、G_IICG under (a) and different mixing ratios_CA () carries out the least square fitting of three-dimensional data, wherein G_IC(a)、G_IICA () is right The mixing ratio answered is respectively 0 and 1, so that it is determined that accurate suitable for the improvement B-K of this kind of CFRP multi direction laminates delamination judge Parameter η value in then.

Further, the step 4 enters interlayer faults toughness data under some mixing ratios of the CFRP multi direction laminates Parameter η value and G in the improvement B-K criterions that row least square fitting is obtained_IC(a)、G_IICA () expression formula is used as improvement B-K criterions In important parameter, be embedded in criterion by finite element User Defined subprogram USDFLD, set up be based on cohesive force unit FEM model to simulate this kind of multi direction laminate difference mixing ratio under delamination behavior.

Further, the improvement criterion may be used on predicting that the multidirectional laminates of this kind of CFRP expand in any mixing ratio lower leaf Exhibition behavior.For other materials or the multidirectional laminate at other interfaces, the improvement criterion was passed judgment on by dividing that fiber bridge joint is affected There is versatility in layer extension.

Present invention advantage compared with prior art is：

(1) the delamination row affected by fiber bridge joint on multidirectional laying plate cannot be realized for existing delamination criterion Limitation to carry out effective simulation proposes a general improvement B-K criterion.

(2) present invention is using the I/II mixed type test numbers under multi direction laminate I types, II types and limited difference mixing ratio Obtain improving the η values in B-K criterions according to fitting, can be predicted this kind of multi direction laminate Mixed-Mode Delamination extension under any mixing ratio Behavior, therefore test job amount is significantly shorten, reduce experimentation cost.

(3) the overtesting checking that predicts the outcome of the invention, predicted value has preferable uniformity with test measured value, because The precision of this Forecasting Methodology of the present invention is higher.

Description of the drawings

Fig. 1 is that a kind of improvement B-K criterions of the invention affect the multidirectional Laminates With Delamination prediction of composite for fibre-bearing bridge joint Method flowchart；

Fig. 2 is the physical dimension of sample and hinge schematic diagram (in units of millimeter)；

Fig. 3 is that loading scheme is tested in I, II type and the layering of I/II type mixed types static(al), wherein, Fig. 3 (a) is that the layering of I types is expanded Exhibition DCB experimental rig schematic diagrames, Fig. 3 (b) is II type delamination 4ENF experimental rig schematic diagrames, and Fig. 3 (c) is I/II mixed types Delamination MMB experimental rig schematic diagram, Fig. 3 (d) is I type delamination DCB experimental rig pictorial diagrams, and Fig. 3 (e) is II types point Layer extension 4ENF experimental rig pictorial diagrams, Fig. 3 (f) is that I/II Mixed-Mode Delaminations extend MMB experimental rig pictorial diagrams；

Fig. 4 is to be layered interlayer faults toughness data figure and matched curve, wherein, Fig. 4 (a) is that I types layering interlayer faults are tough Degrees of data figure and matched curve, Fig. 4 (b) is II types layering interlayer faults toughness data figure and matched curve, and Fig. 4 (c) is mixing ThanI/II Mixed-Mode Delamination interlayer faults toughness data figures with 0.75；

Fig. 5 is that least square fitting determines the η values improved in B-K criterions；

Fig. 6 is I/II Mixed-Mode Delamination expanding test load displacement curves and finite element modelling comparative result figure, wherein, figure 6 (a) is mixing ratioI/II Mixed-Mode Delamination expanding test load displacement curves and finite element with 0.75 Analog result comparison diagram, Fig. 6 (b) is mixing ratioI/II Mixed-Mode Delamination expanding test load displacement curves and limited First analog result comparison diagram.

Specific embodiment

The present invention is described in further detail with reference to embodiment：

A kind of improvement B-K criterions of the present invention are used for fibre-bearing and bridge the method for affecting the multidirectional Laminates With Delamination prediction of composite Implement step as follows：

Step 1：Sample be by made by the unidirectional pre-immersion material of T700/9511 carbon fibers/bismaleimide resin system, Ply stacking-sequence is (+45/-45/06)_S//(-45/+45/06)_SCFRP multi direction laminates, in order to ensure displacement load effectively The mid-plane of cantilever beam is applied to, a kind of Fast Installation hinge is employed in DCB and MMB tests, as shown in Figure 2；According to ASTM standard D5528-01 carries out I types delamination test (DCB) to CFRP multi direction laminates, using 4ENF experimental rigs pair CFRP multi direction laminates carry out the test of II types delamination, and CFRP multi direction laminates are carried out according to ASTM standard D6671M-06 Mixing ratioI/II mixed type static(al)s delamination for 0.25,0.4,0.5,0.6 and 0.75 tests (MMB), by adjusting loading Point realizes the required mixing ratio of test away from sample stage casing apart from c, and DCB, 4ENF and MMB experimental rig is as shown in Figure 3.

Step 2：Process test data and determine layering interlayer faults toughness G changed with layering length a_IC(a)、G_IIC(a) and G under different mixing ratios_C(a).The process of implementing is：I type interlayer faults toughness G_ICA () expression formula is：

Wherein：B is specimen width, and F and N' is respectively modifying factor when considering that big displacement and loading blocks affect, due to What is measured in present claims is layering vertical range of the tip away from loaded line and employs hinge rather than loading blocks, the two because Son is 1.P_ICAnd δ_ICIt is respectively the I types load and displacement that sample is applied, | △ | is the modifying factor for being layered length, is used for Consider that cantilever is splitting the displacement additional due to material anisotropy of sharp position and rotation.

According to I type delamination test datas, flexibility C with a certain layering testpieces for determining layering length a is calculated, Then a series of C of linear fit^1/3| △ | is obtained with crack length a, further according to G_ICA () expression formula calculates different crack length a Corresponding G_IC(a), as a result as shown in Fig. 4 (a).

II types are layered interlayer faults toughness G_IICA () expression formula is：

Wherein：P_CIt is critical load, C is sample flexibility.

According to II type delamination test datas, the flexibility with a certain layering testpieces for determining layering length a is calculated C, then a series of C of linear fit and crack length a are obtainedFurther according to G_IICExpression formula calculates different crack lengths a pair The G for answering_IIC(a), as a result as shown in Fig. 4 (b).

I/II mixed type interlayer faults toughness G_CA () expression formula is：

G_C(a)=G_I(a)+G_II(a)

Wherein：P is the load applied at the point of application, and c is the point of application to the middle distance for loading roller bearing, P_gBe entablature and It is attached to the weight of wherein loading blocks, c_gCenter of gravity for fixture loads the distance of roller bearing, E to centre_fIt is bending modulus, h is that sample is thick That what is spent is general, and L is fixed span away from as shown in accompanying drawing 3 (c).

According to I/II Mixed-Mode Delamination expanding test data, strain energy release rate I type component G are calculated respectively_I(a) and II Component G_II(a), further according to G_CA () expression formula calculates the corresponding G of different crack length a_C(a), such as shown in Fig. 4 (c).

Step 3：Be fitted respectively above-mentioned I types, II type delamination test datas are obtained with layering length change layering Interlayer faults toughness obtains G_IC(a)、G_IICShown in the mathematic(al) representation of (a) such as Fig. 4 (a) and (b)；Based on improvement B-K criterions to upper State the G of known mixing ratio_IC(a)、G_IIC(a) and G_CA () carries out the least square fitting of three-dimensional data, so that it is determined that being applied to institute Parameter η value in the improvement B-K criterions of the multidirectional laminates of research CRFP, as shown in Figure 5.

Step 4：Set up based on the FEM model of cohesive force unit, by User Defined subprogram USDFLD, will be upper State CFRP multi direction laminate I types and II type interlayer faults toughness G_IC(a)、G_IICPass through a most young waiter in a wineshop or an inn in the expression formula of (a) and step 3 The parameter η value in the improvement B-K criterions that fitting obtains is taken advantage of to be embedded in improvement B-K criterions, using the improvement as important parameter B-K criterions simulate the delamination behavior under this kind of multi direction laminate difference mixing ratio, and by contrast test and numerical result The accuracy for improving B-K criterions is set up to verify.The improvement B-K criterions are：

For mixing ratioI/II Mixed-Mode Delaminations extension with 0.75, will improve B-K criterions and uses In Abaqus, set up based on the FEM model of cohesive force unit, the load displacement relation that numerical simulation is obtained and experiment number According to such as Fig. 6 (a) Suo Shi.In initial line elastic stage and delamination stage, analog result has good with test result Uniformity.

Using the improvement B-K criterions of the inventive method proposition to the CFRP multi direction laminates for mentioning in above-mentioned steps 1 Carry out mixing ratioI/II mixed type static(al) delaminations test bit prediction., mixing ratio is 0.6 I/II mixed types The numerical result of delamination load displacement with experimental data to such as Fig. 6 (b) Suo Shi, there it can be seen that in Stiffness Deterioration Before the initial slope of numerical curve has good uniformity and keeps constant with experimental result, and the initial damage of prediction is carried Lotus and ultimate load are preferable with agreement with experimental data.Can be to the delamination behavior under any mixing ratio using B-K criterions are improved Predicted well.

Non-elaborated part of the present invention belongs to the known technology of those skilled in the art.

Claims (8)

1. a kind of improvement B-K criterions are used for the method that fibre-bearing bridges the multidirectional Laminates With Delamination prediction of impact composite, its feature It is to comprise the following steps：

Step 1, is carried out by the test of double cantilever beam bending (DCB), 4 end edge otch (4ENF) and Mixed Bending (MMB) The test of the I types of the multidirectional laminates of CFRP, II types and I/II mixed type static(al)s delamination, obtains corresponding load, displacement and crackle Length test data；

Step 2, data processing is carried out to test data and determines I type interlayer faults toughness G changed with layering length a_IC(a)、II Type interlayer faults toughness G_IICMixed type interlayer faults toughness G under (a) and different mixing ratios_C(a)；

Step 3, step 2 is obtained G using the improvement B-K criterions of fiber bridge joint in consideration delamination_IC(a)、G_IIC(a) and G under different mixing ratios_CA () carries out the least square fitting of three-dimensional data, so that it is determined that be applied to studying the multidirectional layers of CRFP Parameter η value in the improvement B-K criterions of plate；

Step 4, sets up based on the FEM model of cohesive force unit, by User Defined subprogram USDFLD, will be above-mentioned CFRP multi direction laminate I types and II type interlayer faults toughness G_IC(a)、G_IICPass through least square in the expression formula of (a) and step 3 Parameter η value in the improvement B-K criterions that fitting is obtained is embedded in improvement B-K criterions, using improvement B-K as important parameter Criterion simulates the delamination behavior under this kind of multi direction laminate difference mixing ratio, and is tested by contrast test and numerical result Card sets up the accuracy for improving B-K criterions；

Step 5, using the improvement B-K criterions having verified that the static(al) delamination behavior under any other mixing ratio is predicted.

2. a kind of B-K criterions of improving according to claim 1 are used for the multidirectional laminate point of fibre-bearing bridge joint impact composite The method of layer prediction, it is characterised in that：Checking improves the ply stacking-sequence of the CFRP multi direction laminates that criterion is adopted for (+45/- 45/0₆)_S//(-45/+45/0₆)_S, the design of this kind of ply stacking-sequence is to reduce bending-torsional coupling effect and because laying is not right The reciprocal curvature effect cited approvingly.

3. a kind of B-K criterions of improving according to claim 2 are used for the multidirectional laminate point of fibre-bearing bridge joint impact composite The method of layer prediction, it is characterised in that：The ply stacking-sequence is (+45/-45/0₆)_S//(-45/+45/0₆)_SThe multidirectional layers of CFRP Plywood is made of the unidirectional pre-immersion material using T700/QY9511 carbon fibers/bismaleimide resin system.

4. a kind of B-K criterions of improving according to claim 1 are used for the multidirectional laminate point of fibre-bearing bridge joint impact composite The method of layer prediction, it is characterised in that：The step 2 is determined using amendment beam theory breaks with the I types interlayer of layering length a change Split toughness G_ICA () expression formula is：

$G_{IC}\left(a\right)=\frac{3P_{IC}{\mathrm{\&delta;}}_{IC}}{2b(a+|\mathrm{\&Delta;}\left|\right)}\frac{F}{N^{\&prime;}}$

Wherein：B is specimen width, and F and N' is respectively modifying factor when considering that big displacement and loading blocks affect, due to measurement It is to be layered the sophisticated vertical range away from loaded line and employ hinge rather than loading blocks, the two factors are 1, P_ICAnd δ_ICPoint It is not the I types load and displacement that sample is applied, | △ | is the modifying factor for being layered length, for considering that cantilever is splitting sharp position The displacement additional due to material anisotropy and rotation；

The step 2 determines II type interlayer faults toughness G with layering length a change using flexibility method_IICA () expression formula is：

$G_{IIC}\left(a\right)=\frac{P_c^2}{2b}\frac{\&part;C}{\&part;a}$

Wherein：P_CIt is critical load, C is sample flexibility；

The step 2 determines I/II mixed type interlayer faults toughness G with layering length a change according to amendment beam theory_C(a) table It is up to formula：

$G_I\left(a\right)=\frac{12{\&lsqb;P(3c-L)+P_g(3c_g-L)\&rsqb;}^2}{16b^2{h}^3{L}^2{E}_f}{(a+|\mathrm{\&Delta;}\left|\right)}^2$

$G_{II}\left(a\right)=\frac{9{\&lsqb;P(c+L)+P_g(c_g+L)\&rsqb;}^2}{16b^2{h}^3{L}^2{E}_f}{(a+0.42|\mathrm{\&Delta;}\left|\right)}^2$

G_C(a)=G_I(a)+G_II(a)

Wherein：P is the load applied at the point of application, and c is the point of application to the middle distance for loading roller bearing, P_gIt is entablature and is attached to The wherein weight of loading blocks, c_gCenter of gravity for fixture loads the distance of roller bearing, E to centre_fIt is bending modulus, h is sample thickness, L For fixed span away from.

5. a kind of B-K criterions of improving according to claim 1 are used for the multidirectional laminate point of fibre-bearing bridge joint impact composite The method of layer prediction, it is characterised in that：It is fitted above-mentioned I types, II type delamination test datas in the step 3 respectively to obtain With the G of layering length change_IC(a)、G_IICThe mathematic(al) representation of (a), the G of the CFRP multi direction laminates_ICA () expression formula is to divide Section function, is divided into fiber bridge joint sections and stablizes expanding section；The G of the CFRP multi direction laminates_IICA () expression formula is by linear Fitting is obtained.

6. a kind of B-K criterions of improving according to claim 1 are used for the multidirectional laminate point of fibre-bearing bridge joint impact composite The method of layer prediction, it is characterised in that：Based on improvement B-K criterions to above-mentioned gained delamination fracture toughness in the step 3 Data G_IC(a)、G_IICG under (a) and different mixing ratios_CA () carries out the least square fitting of three-dimensional data, wherein G_IC(a)、G_IIC A () corresponding mixing ratio is respectively 0 and 1, so that it is determined that the improvement passed judgment on suitable for this kind of CFRP multi direction laminates delamination Parameter η value in B-K criterions.

7. a kind of B-K criterions of improving according to claim 1 are used for the multidirectional laminate point of fibre-bearing bridge joint impact composite The method of layer prediction, it is characterised in that：The step 4 is by interlayer faults toughness under some mixing ratios of the CFRP multi direction laminates Data carry out parameter η value and G in the improvement B-K criterions that least square fitting is obtained_IC(a)、G_IICA () expression formula is used as improvement Important parameter in B-K criterions, is embedded in criterion by finite element User Defined subprogram USDFLD, is set up and is based on cohesion The FEM model of power unit to simulate this kind of multi direction laminate difference mixing ratio under delamination behavior, the improvement B-K Criterion is：

$G_{IC}\left(a\right)+\left(G_{IIC}\right(a)-G_{IC}(a\left)\right){\left(\frac{G_{II}\left(a\right)}{G_I\left(a\right)+G_{II}\left(a\right)}\right)}^{\mathrm{\&eta;}}=G_C\left(a\right)$

8. a kind of B-K criterions of improving according to claim 1 are used for the multidirectional laminate point of fibre-bearing bridge joint impact composite The method of layer prediction, it is characterised in that：The improvement criterion may be used on predicting the multidirectional laminates of this kind of CFRP in any mixing ratio Lower leaf propagation behavior, for other materials or the multidirectional laminate at other interfaces, the improvement criterion is bridged in judge by fiber There is versatility in the delamination of impact.