Viscoelastic Analysis Of The Macro-micro Residual Stress In Composite Laminated Plate

The residual stresses generated during manufacture are inherent to any polymer matrix composites(PMCs)because of the inherent anisotropy of the unidirectional composite laminate and the differences in the thermo-chemical and mechanical properties between the reinforcement fiber and the matrix.The presence of residual stress can significantly degrade the strength and dimensional accuracy of PMCs.Thus,it is important to accurately predict the development history and final distribution of residual stresses in PMCs for the process optimization and application.In order to analysis the development history and final distribution of residual stresses in PMCs during manufacture,a degree of cure and temperature dependent linear viscoelastic constitutive model is developed.By using the developed constitutive model,the history and final distribution of the macroscopic and microscopic residual stress developed in an AS4/3501-6 composite are analyzed.The effect of the macroscopic process induced deformation on the microscopic residual stress is studied based on a macro-micro coupling model.The main results and conclusions include:1.A degree of cure and temperature dependent linear viscoelastic constitutive model is developed,and the parameters referred to as the Deborah numbersmDe were proposed,which can comprehensively reflect the viscoelasticity of a composite during curing2.The history and final distribution of the macroscopic residual stress developed in an AS4/3501-6 composite are analyzed.The results show that the predicted macroscopic residual stress is consistent with those of the open reported literature,and the evolution characteristic of the macroscopic residual stress can be reasonably explained based on the evolution of the Deborah numbersmDe3.A micro model of an unidirectional composite laminate is established,and the history and final distribution of the microscopic residual stress are analyzed.The results show that 95% of the microscopic residual stress in the polymer matrix is developed during the cooling process.The maximum 1st principle stress occurs in the region between the closing fiber,and the maximum hydrostatic tensile stress occurs in the center of the polymer rich region.4.A micro model of a composite laminate interface is established,and the history and final distribution of the microscopic residual stress are analyzed.The results show that the matrix between the crossing fiber is in a pressure state.The location of maximum 1st principle stress is very close to that of the maximum hydrostatic tensile stress in the fiber/matrix interface.The high 1st principle stress and the hydrostatic tensile stress appear at the region of 45°~135° to the thickness direction,and may cause the interface damage.5.A macro-micro coupling model of a composite laminate is established,and the effect of the macroscopic deformation on the microscopic residual stress is analyzed.The result shows that the predicted residual stress in the matrix of the macro-micro coupling model is much different from that of the micro model.