Numericial Investigation And Optimization Desigsin On Progressive Failure Response Of Composite Bolted Joint

The application of composites is an important symbol of the advanced materials in modern time,however,due to the anisotropy and low inter-ply strength of composite materials,the strength analysis of composite joints shows significant nonlinearity,which is different from that of metal materials.Therefore,it is of great significance to analyze the failure of composite bolt connectors.In order to establish an accurate numerical simulation model,the progressive damage subprogram of carbon fiber reinforced composites(CFRP)is compiled based on ANSYS software.The damage evolution process of composite single-joint under tensile load is studied numerically.The specific contents and results obtained are as follows:(1)Based on the the damage theory of composite material including constitutive relation,failure criterion and stiffness variable,the three-dimensional Hashin failure criterion is extended,and a three-dimensional progressive failure analysis model is eatablished considering the friction,bolt pretension and shear nonlinearity.The results showed that this 3D finite element model established in this paper can accurately simulate the failure process of composite single-bolt joint under tensile load,and can be used in failure analysis of complex composite structure bolt connections.(2)Based on the extended 3D Hashin failure criterion in this paper,a post-processing subprogram for data post-processing is developed using "element screening method".visual analysis of numerical simulation results The process of initial damage,crack propagation and ultimate failure of laminated plates during uniaxial tension can be analyzed more intuitively.(3)The progressive damage subroutine was debugged by APDL language in ANSYS,and the parametric analysis of bolt joint was completed to analysis the effects of lamination angle,friction coefficient between contact surfaces and bolt clamping load on the the bolt joint of lightweight composite laminated plates and metal plate according to analysis the stress distribution around bolt-hole and the failure mode of the joint.The results show that different proportion of laying angle in laminates will lead to different failure mode of composite material laminated plates.When designing the composite layer,it's better to prevent the low strength failure mode accoured.Within the range of recommended preloading force on the composite bolt joint,the joint strength of composite bolt can be enhanced by increasing the pretightening force appropriately.Increasing the friction coffefficient(?)between the contact surfaces can effectively slow down the damage and failure process around the bolt holes of laminated plates.This study will provide theoretical basis for structural design and optimization of composite joints.