Nonlocal Progressive Failure Modeling And Finite Element Analysis Of Composite Laminates

Carbon fiber composite made of carbon fiber reinforcement and resin matrix is a kind of structural material that has got focus in the new material’s research and development field. It has a series of excellent performance, such as high strength, high stiffness, low density, low thermal expansion coefficient and so on. Therefore, it has good development prospects. However, the failure mechanism of composite laminates is complex, including intralaminar damage and delamination. At the same time, composite after initial failure can continue to bear load, which challenges the assessment and prediction of strength, stiffness, damage tolerance and residual life. Now, there are many researches on the progressive failure analysis of composite due to their complex failure mechanism. However, the composite laminate structure and geometry in the actual design and application is not regular.They often, contain holes and cutouts. This is physical objective phenomenon which shows local high gradient stress, strain concentration in these discontinuous component. If these problems are not well solved, traditional continuum mechanics and finite element analysis based on the structure will become meaningless. Thus, the finite element analysis results become dependent on the mesh size and the progressive failure analysis loses its significance.So far, at home and abroad little research is focused on the progressive failure analysis of composite laminates by considering the strain localization problem. This paper, based on the nonlocal integral theory, originally puts forward a nonlocal progressive failure theory of composite laminates, including a non-linear non-local damage thermodynamic model on the intralaminar damage and a nonlinear interlaminar cohesive model. The main research methods and conclusions are drawn as follows:(1) The progressive failure analysis model of composite laminate is established, in which the failure criterion is determined by equivalent strain and damage evolution law for fiber fracture and matrix cracking variable is derived. In addition, consistent tangent modulus is deduced. These work provides theoretical support for strength prediction of composite.(2) Based on the nonlocal integral theory proposed by Princeton University Eringen AC and Northwestern University BazantZP academician, this paper essentially introduces two length scale parameters for the fiber breakage and matrix cracking into the governing equation to solve the localization problem. According to the implicit finite element solution, anisotropic nonlocal consistent tangent modulus is deduced. The strategy can provide a theoretical basis to solve composite strain localization problems.(3) By combining UEL (User element subroutine), UMAT (User material subroutine), USDFLD (User field subroutine) and UEXTERNALDB (User external data utility subroutine) in the ABAQUS finite element software, the nonlocal anisotropic progressive failure model is implemented and the numerical calculation technique of carbon fiber reinforced composite nonlocal progressive failure analysis is formed.(4) Combined with the mechanical experiment of composite laminates with central hole, based on the nonlocal anisotropic progressive failure model, we explore the progressive failure behaviors of composite laminates with central hole under tensile load and investigate the effect of hole radius, layup pattens, mesh size and the nonlocal scale parameters on the progressive failure characteristics of laminated composite.