Research On Damage Fatigue Propagation Of Composite Structures Based On Discrete Damage Zone Model

Composite laminated structure has been widely used in many fields due to its strong specific strength,strong specific stiffness,impact-resistance,and well-designability.The common damage modes of composite laminated structures are interface delaminations and transverse cracks,which can cause catastrophic effects to structure.In this paper,a progressive extended layerwise method(PXLWM)has established to analyze progressive damage of composite structures under static and fatigue loading.The main contents include the following three aspects:Firstly,the discrete damage zone model(DDZM)was combined with the extended layerwise method(XLWM)by adding spring elements to the damage area.Establish the finite element equations and solve by Newton-Raphson iterative method.The PXLWM was established to analyze the progressive delamination of composite laminates.In numerical examples,the contact problem of composite laminates and double cantilever beam with delamination is analyzed.Compared the PXLWM results with analytical solutions,so that to verify the correctness of PXLWM.Then,by studying the effect of mesh size in width direction of double cantilever model on calculation results,the modified formulation for initial stiffness of discrete damage zone model is obtained.The two-dimensional PXLWM is extended to three-dimensional,which can be used to analyze the progressive delamination of composite laminates.In numerical example,the progressive delamination of double cantilever beams with different stacking sequence,composite laminates with different length-width ratios and aspect ratios is analyzed,and studied the influence of transverse cracks on progressive delamination.Finally,peerlings damage law is introduced into PXLWM to adjust the damage evolution relationship of the DDZM.The PXLWM can be used to analyze the fatigue damage and model fatigue parameters of DDZM which can match the experimental results.The fatigue parameters were modified by adjusted the mesh size.In numerical example,the fatigue life of double cantilever beam is analyzed.Several groups of S-N curves are determined,and the influence of stacking sequence on fatigue life of the model is studied.