Research On Failure Analysis Method Of Composite Materials Based On Peridynamics

Composite materials have higher specific stiffness and specific modulus than single materials,and are important engineering structural materials,but the mechanism of composite failure generation and expansion is very complicated.Methods based on traditional continuum mechanics theory(such as finite element method)require additional failure criteria and additional functions when solving crack propagation problems.Even so,traditional methods cannot accurately simulate three-dimensional cracks and group cracks.The peridynamics theory(referred to as PD theory)replaces the differential term in the traditional continuum mechanics constitutive equation with the integral term,avoiding the derivative singularity caused by the crack.The application of peridynamics theory to failure-progression simulation has three major advantages:(1)No additional failure criterion,spontaneous generation of crack propagation and expansion;(2)Modeling of problems of different scales;(3)Under the same computational framework,it is possible to simultaneously process the propagation of multiple cracks and consider the interaction between them.Peridynamics theory has achieved certain achievements in composite material simulation analysis.So far,there have been two peridynamics models of composite materials,the one based on fiber bond and matrix bond and both in another based on normal bond and shear bond.The model based on fiber bond and matrix bond is the earliest composite PD model.It describes the material information by adding appropriate modification items to the constitutive force function.Its modeling method is simple and easy to understand,and it can simulate variety of failure modes of the composite material.So it is the most studied model category.However,a common problem in this modeling method is that the fiber-reinforced composite material is mechanically divided into two materials,a fiber material and a matrix material.The bond stiffness of the matrix bond and the fiber bond are constant,and the variation of mechanical properties between the two are stepped.This ignores the influence of fiber materials on the matrix material,and this paper aims to construct a new composite model that is close to the mechanical properties of the fiber material.The main purpose of this thesis is to explore a new fiber reinforced composite model based on the PD theory of bond-based,which is convenient for the analysis of the failure mode of composites.Similar to the previous composite model based on the bond-based PD theory,the matrix bond and fiber bond are also used to describe the mechanical properties of the matrix material and the fiber material,respectively.However,the biggest difference from the previous model is that the influence of fiber material on the mechanical properties of the matrix material is taken into account in the process of constructing the model.The trigonometric function is used to represent the bond stiffness change of the matrix bond,while the bond stiffness of the fiber bond is still expressed by a constant.Then,according to the strain energy density at the material point is equivalent obtained by the PD theory and the continuous mechanics theory,the specific expression of the bond stiffness is solved,and the new fiber-reinforced composite model is constructed.In order to verify the validity of the model applied to the problem of no failure elastic deformation,the predictions of the PD method are compared with the theoretical solution and the simulation results of Abaqus for the same loading problem.The results of the comparison show a good correlation,and verifying that the model can solves the quasi-static problem.Then,the PD method is used to simulate the failure propagation mode of the lamina with pre-existing crack,and the failure mode consistent with the experimental results is obtained.It is effective to verify the model simulation failure progression problem.The proposed model can simulate the problem of no failure and failure,and prove that the proposed PD model can play an active role in the failure study of composite materials.