The Failure Damage Analysis Of The Composite Laminates

Due to high specific strength,specific stiffness and flexibility in their design,fiber reinforced composites have been widely used in various engineering structures.In the practical engineering application,composite laminates are in a multidirectional stress state in most cases,in which the material failure mechanism is very complex.Moreover,the performance degradation of stiffness and strength is more complex.In this paper,the progressive failure process of composite laminate is studied by analyzing the damage initiation,damage evolution and ultimate failure mode of composite laminated under three different loads.The main research contents of the dissertation are as follows:(1)Finite element analysis of composite laminate with open-hole subjected tensile load.By considering the stiffness degradation,failure strain is used to determine the failure of laminates,which based on three-dimensional Hashin criterion as the layer failure criterion,and the three-dimensional progressive damage model of composite laminate with open-hole is established.Variation of fiber and matrix damage factor versus displacement plots are obtained.The failure strength of laminate influenced by different stacking methods and stacking angel is analysized,respectively.The influence of the opening diameter and opening position on the ultimate bearing capacity of laminates under axial tensile load is studied.(2)Finite element analysis for laminates under biaxial tension-tension load.The finite element model of composite cruciform specimen laminates under biaxial tensile loading was established by ABAQUS finite element software,and combining with the user material subroutine(UMAT).The progressive failure process of cruciform specimens under different loading ratios is studied.The influence of different stacking angel on the failure strength of cruciform specimen is also analyzed,and the load-displacement plots for different loading ratio under biaxial tension-tension load is obtained.(3)Finite element analysis of low-velocity impact on laminates.On the ABAQUS/Explicit platform,a three-dimensional finite element model of bullet target was established with the VUMAT subroutine.The contact force and the system kinetic energy versus time plots are obtained.The stress maps of laminates under impact is also analyzed.(4)Finite element analysis of low-velocity impact on bolted joint laminates.Finite element model of low-velocity impact on bolted joint laminates is established by ABAQUS finite element software.The model consists of four parts: the punch,bolt,composite layer and the cohesive layer.Through the simulation calculation,the velocity of the punch and the contact force versus time plots are obtained for different impact energy and boundary conditions.The matrix tensile failure in the impact process is also studied.