Research On Impact Resistance Performance Of Fiber Reinforced Composite Laminate Under High-speed Projectile

Fiber-reinforced composite materials are widely used in a variety of large-scale structures for mainly bearing parts.Because of the widely use of composite material,its impact resistance performance has drawn scholars' attention from various countries.Compared with metals,fiber-reinforced composite material has many advantages such as light weight,corrosion resistance,fatigue resistance,etc.But it also has some complex characteristics such as uncertain damage model,the anisotropic material characteristics.Besides,different reinforce material has different strain-rate correlation.In this thesis,the impact resistance performance of Kevlar and fiberglass under high-speed projectile is studied.The residual velocity of projectile,the energy absorption of target and influence of the target failure mode to the performance of the target under high-speed projectile are studied using the engineering approximation analysis and simulation computation.First,an analytical model was developed to predict the residual velocity.The model was based on energy conservation principle,then the loss of the projectile's kinetic energy during the impact process leads to projectile deformation and target deformation.The target deformation includes two parts: local region damage and global buckling.In this thesis,the energy absorber of target deformation was divide to five components: compression deformation,fiber failure,shear stuffed,fiber fracture injury and delamination.A MATLAB program was written to predict the residual velocity and the energy absorbed by discrete the impact process.In order to improve the accuracy of the formula,the coefficient of dynamic enhanced was introduced to correct the MATLAB program.The model was verified by compared with the experiment results from the open literature.Second,the constitutive model and strength criterion were summarized,the damage evolution and the post-damage softening of simulate computation was studied.In this thesis,the 2D-Hashin criterion was extended to 3D situation.The keywords in VUMAT was modified in order to invoke in simulation software.Finally,the ballistic penetration of laminate composite plates was simulated using shell and solid elements,respectively.Also,the validity of simulation was verified by compared with experiment results.The difference,advantage and disadvantages between the two ways was discussed.The results show that the method which uses shell elements can shorten the calculate time,nevertheless using shell elements can`t reflect the damage through the thickness direction.Using solid elements can make the damage of target along the thickness direction visible.Solid elements were chosen to simulate the impact resistance performance of composite target in order to discuss the damage of target along the thickness direction.The interface stiffness was simulated by using cohesive elements.The influence of rigid projectile and elastic-plastic projectile on ballistic performance was compared.Furthermore,the influence of target thickness and bullet shape on impact resistance performance of the composite target was studied by using rigid projectile,the influence of impact velocity,and ply orientation angle on impact resistance performance of the composite target was studied by using elastic-plastic projectile.