Damage Analysis Of Composite Structure Based On Peridynamics

As material technology advances,the application field of composite materials is gradually expanding.At the same time,the analysis and calculation of mechanical properties such as damage and fracture of composite structures in engineering applications have also become the hot spots of research.Some methods,such as extended finite element method,which are developed on the basis of finite element method,still have difficulty in solving the complex fracture of composite materials.The peridynamic theory,a meshless method based on nonlocal theory,which is introduced in 2000 can solve the difficulties of classical continuum mechanics for calculating the discontinuous problem,such as crack and fracture,very well.It describes the matter mechanical behavior by solving spatial integral motion equations,which avoids solving the partial differential equations at discontinuous position does not exist in the classical continuum mechanics.At the same time,the constitutive model of this method contains the definition of damage,which reveals the process of structure damage and fracture evolution from physical aspect without introducing any additional failure criterion,and this method has obvious advantages compared with other grid methods.Therefore,my thesis use peridynamic method to analyze the damage and fracture process of fiber-reinforced composites which are commonly used in the field of shipbuilding and ocean engineering to get the effective method to calculate the damage and fracture of composite structures.At the beginning of this dissertation,the introduction and development of peridynamics are introduced briefly.The status of domestic and overseas research for the method and the coupling method between peridynamics and other method such as finite element method are elaborated respectively.Based on this work,the basic physical expression,basic principle,discrete method and stability of solution of peridynamic theory is expounded.Due to its anisotropic mechanical properties,bond-based peridynamics model is built for fiber-reinforced resin-based composites.The bond parameter analytical expression and surface effects correction of bond-based peridynaimcs model for 2D and 3D composites are derived.And according to the theory,the 2D lamina and 3D laminates programs are compiled,which are verified by comparing the elastic range of response results with finite element results.On this basis,the definition of multiple damage modes of composite materials is introduced to the programs,and the damage and fracture analysis of lamina with a pre-existing crack and double cantilever beam are achieved.The convergence of the bond-based peridynamics of the composite was investigated by selecting different radius of the horizon and density of discrete.And the convergence of the peridynamic method was found to be highly consistent.And the accuracy and efficiency of the calculation related to the above factors are obtained.Then the analysis of the and damage,cracks and failure mode influence of lamina with different angle pre-existing crack and laminates with different layup configuration containing a hole in the center were developed.And the results show that under the tensile load the fiber reinforced composite material usually occur the matrix damage,the laminates with dispersed angle plies are common occurring delamination damage.Then peridynamic program of composite damage was applied to calculating the damage of simplify bolted joint structure,and the common damage propagation process and failure mode of the structure were obtained.In order to improve the applicability and computational efficiency of peridynamic damage analysis,the coupling approach of peridynamics with finite element method was studied.The interface element achieves the transfer of force and displacement between peridynamics subdomain and finite element subdomains,and the displacement field of two subdomain border was compatible.And this coupling method was applied to the damage analysis of two-dimensional lamina,which greatly improves the analysis efficiency and achieves the expected results.