Predict And Research Of The Effective Shear Stiffness Of Symmetric Laminate With Open Non-ideal Matrix Cracks

In this paper,the theoretical model of the stiffness and mechanical properties of symmetry laminates with open non-ideal matrix cracks is applied to consider the influence of the resistance between the rough crack surfaces on the material properties.The effective shear stiffness is studied to make the theoretical results more in line with the material actual test situation.The research contents are summarized as follows:(1)Review the development process of composite laminate research,systematically review the main theoretical methods,and understand the various damage mechanisms and failure modes of laminates.(2)The basic equations and energy variational principles of anisotropic composites are given.The single-layer plate is composed of fibers and a matrix,and the fibers are distributed in the matrix in the same direction,and macroscopically satisfy the basic equations of the anisotropic composite materials,equilibrium differential equations,geometric equations,and physical equations.(3)For the symmetry laminates[?_m90_n]_swith open non-ideal matrix cracks angles,the interlaminar shear stress is set in the general function form,and the stress component expression of the open crack is obtained from the equilibrium equation and the boundary conditions,using the principle of minimum residual energy.The control equation of the open crack is derived and solved by analytical analysis to obtain the stress distribution of the composite symmetric laminated plate.(4)Analyze the effect of shear modulus of fiber laminates on composite laminates,and verify the correctness of the theoretical model by comparing theoretical model data with finite element data and experimental data.And calculate the effect of bridging factor on effective shear modulus.The non-ideal opening of the matrix crack,the crack surface is not smooth and is bridged by the fiber,which has a significant effect on the degradation of the shear modulus of the laminate.The determination and evaluation of the shear modulus of the laminated symmetrical laminated plates with open non-ideal base crack angles can reasonably design the laminated plates,improve their overall strength,extend the service life of the laminated plates,increase its application range and ensure its safe.