Research On Tensile And Ballistic Impact Damage And Failure Of 2D Woven Composites

Lightweight and high strength are the significant theme on the development of armored equipment.Two-dimensional(2D)woven composites are widely used in armor equipment due to their lightweight and high strength.However,the complex structure and damage evolvement of them make it difficult to investigate their damage and failure behavior.The paper takes the S-glass/epoxy,Kevlar/epoxy and their hybrid composites as research objects.The paper learns their mechanical property and damage behavior under quasi-static tensile through experiments and numerical simulations,and the numerical simulations on the ballistic impact damage are carried out.Firstly,the domestic and foreign researches on the test and simulation of composites under quasi-static tensile and ballistic impact,including test methods and results,finite element methods,progressive damage and failure models,are introduced.Secondly,the quasi-static tensile experiments of 2D woven composites are carried out.The stress-strain curve,tensile stiffness and strength of them are obtained.The scanning electron microscope(SEM)was used to observe the fracture morphology of the specimens,and their failure mode and mechanism are studied.Then,the unit cell finite element models are established,according to the mesoscopic structure of the 2D woven composites.A progressive damage failure model for 2D woven composite is proposed.In this model,damage modes such as fiber breakage,inter-fiber fracture,and matrix fracture are considered.The relationship between the equivalent elastic strain and the test strain is established,which can simulate the nonlinear part of stress-strain curve caused by yarn crimping at the beginning of tension of Kevlar/epoxy composite.The 3D Hashin and the maximum stress criterion are used as the damage initial criterion of the fiber bundle and the matrix respectively.The exponential model is used as the damage evolution model of the fiber bundle,and the matrix uses a combination of exponential and arctangent functions to simulate its plasticity and damage behavior.The cohesive zone model is used to simulate the delamination damage of hybrid composite laminates.The progressive damage model is realized by writing user defined material subroutine UMAT in ABAQUS software,to simulate the damage evolution process of 2D woven composite under quasi-static tension.The results of simulation are compared with the experiment.Finally,a ballistic impact progressive damage model considering the strain rate effect,is established which is based on the macroscopic laminate model.The model was used to modeling the ballistic process of 2D woven composites,and compared with the experimental results in the literatures,the validity of the damage model is verified.The influence of different layup sequences of hybrid composites on the impact resistance property is studied.