Elastoplastic Analysis Of Thermoplastic Composite Components

Continuous fiber-reinforced thermoplastic(CFRTP)composite has comprehensive mechanical properties and is the ideal candidate materials for the compartment structure of reusable vehicles.The focus of this paper is to establish an enhanced elastoplastic damage coupled constitutive model(EPDM)for CFRTP composite,which takes anisotropic effect of tension and compression,hydrostatic effect,and material damage into account.And the mechanical properties of typical components such as laminated beams,laminated plates,as well as stiffened panels are analyzed.The main research contents are as follows:Theoretical models for the elastoplastic analysis of CFRTP composite plane beams under bending moment are established.Based on the orthotropic Hill yield criterion and the single parameter plastic model under plane stress state,respectively,the elastoplastic theoretical analysis models of CFRTP composite plane straight beam and plane curved beam under bending moment are carried out,which is combined with the linear hardening law.And the analytical solutions of stresses and displacements are obtained.The effects of fiber direction angle,geometrical dimension,and external load on the elastoplastic mechanical response of plane beams are studied,which provides a theoretical basis for the elastoplastic study of complex CFRTP composite components.The elastoplastic damage coupled constitutive model(EPDM)for CFRTP composite is established,which takes anisotropic effect of tension and compression,hydrostatic effect,and material damage into account.The three-dimensional orthotropic Hill yield criterion is improved by introducing stress coefficients.Then based on the nonlinear strain-hardening law,the Chang-Chang failure criterion and the continuum damage mechanics,the EPDM for CFRTP composite is established.Based on the forward Euler method,the corresponding user-subroutine VUMAT is prepared in commercial finite element software by using secondary-development technology.Furthermore,the basic mechanical properties of the CFRTP composite are tested,and the corresponding parameters of the constitutive model are obtained by utilizing the inversion technique.The numerical simulation of plane beams under bending moment and the mechanical tests of multidirectional laminates with and without a hole are carried out.And the correctness of the constitutive model and the implementation method are verified from both theoretical and experimental aspects.The finite element analysis of elastoplastic properties of CFRTP composite laminated structures is carried out.The finite element model of the CFRTP composite laminated beam is established based on the constitutive model.And the anisotropic effect of tension and compression and elastoplastic effect on mechanical response and stress distribution of laminated beams are analyzed.The influence of fiber direction angle and span ratio on deformation and plastic zone variation form of laminated beams is obtained.In addition,the plastic evolution mechanism of laminated beams is investigated.Based on the constitutive model,the finite element analysis model of a CFRTP composite laminated plate with a hole is proposed.The influence of fiber direction angle and aspect ratio on the load capacity,plastic zone variation form,and interlaminar stress of critical path is studied.The judgment method of initial failure position near the hole is discussedExperimental design and finite element analysis of axial compression characteristics of CFRTP composite stiffened panel are carried out.Based on the finite element simulation and experimental study of CFRTP composite L-shaped stiffener under axial compression,the buckling form of L-shaped stiffener is obtained.On the basis of the cohesive element model,the finite element model of CFRTP composite stiffened panel is established,which considers debonding and material damage.The axial compression tests of CFRTP composite L-shaped stiffener stiffened panels are carried out to verify the finite element model.The influence of section shape,boundary condition,and initial debonding position on axial compression characteristics is analyzed.The research results of this paper provide a theoretical basis and a technical support for the analysis and design of CFRTP composite components and have important theoretical significance and engineering application value.