Research On Dispersity Of Compressive Strength Of FRP Based On Finite Element Method

Fiber reinforced plastic(FRP)have the advantages of high modulus,low density,corrosion resistance and easy forming,so they are widely used in large military equipment such as aircraft,vehicles and ships.However,a critical limitation of FRP is its relatively large stochastic variation on mechanical performance(especially its compressive strength),which results in that the safety factor of structural design is often made too high,and it cannot give full play to the excellent characteristics of composite materials.The dispersion feature of compressive strength of FRP and its influencing factors are studied.Based on the Abaqus/Standard environment,a three-dimensional model of fiber reinforced plastic with random fiber distribution is firstly established in the world.The simulation of compressive failure of FRP resulted from fiber micro-buckling is successfully performed.The probability distribution of the compressive strength of carbon fiber and glass fiber reinforced plastic are obtained.Finally,experiments are carried out to verify the theoretical and simulation results.The main contents and conclusions are as follows:1.The characteristics of Rebar and Beam element are compared and the Beam element is selected as the element type of fiber in the finite element model.The influence of four factors including geometrical size,mesh size,finite element type and analysis method,on the results of finite element analysis of unidirectional FRP are studied.The optimal parameters and types are determined.2.A new improved approach named LHS-RSE(Latin hypercube sampling based on random sequential expansion)is proposed to generate random fiber distribution across the cross-section.LHS-RSE provides high computation efficiency and good distribution characteristics in comparison to previously proposed methods.Fiber waviness defect with different misalignment angles is defined by analytic formula and also incorporated in the finite element model.3.Finite element models with 30% and 60% fiber volume ratio are developed.Then,compressive strengths of these models are derived from displacement-force curve.Compressive strength distribution fitting and hypothesis test are performed utilizing compressive strength simulation data.The coefficient of variation of finite element model with 30% fiber volume ratio is larger than that of finite element model with 60%fiber volume ratio.It is shown that random fiber packing tends to result in a stochastic detriment of FRP compressive strength in comparison with uniform fiber packing condition,and the stochastic variation of compressive strength tends to follow normal or lognormal distribution.4.The compressive strength and shear strain distribution of 60% fiber withuniform distribution and randomly distributed carbon fiber reinforced plastic are compared.The effect of fiber misaligned angle on compressive strength of FRP is also studied.Results show that the random fiber distribution will make the shear strain distribution in cross-section unequal and both random fiber distribution and fiber misaligned angle obviously reduce the compressive strength of FRP.5.The compressive strength of carbon fiber reinforced plastic model and glass fiber reinforced plastic model with 60% fiber volume ratio are analyzed.Results show that the compressive strength of GFRP is more dispersive and tends to follow lognormal distribution.6.The compressive experiments are carried out on unidirectional carbon fiber reinforced plastic,and the failure modes of the samples are analyzed.Experimental compressive strength data is obtained from the recorded load-displacement curves,and the distribution fitting and distribution hypothesis testing are performed on the experimental compressive strength data.Compression intensity distribution data tends to obey normal distribution and lognormal distribution,which is consistent with simulation results.