Computational modeling of micro curing residual stress evolution and out-of-plane tensile damage behavior in fiber-reinforced composites

This paper focuses on revealing the evolution mechanism of micro curing residual stress and its impacts on the mechanical responses of medium-temperature cured composites (T700/7901) under out-of-plane tension. An integrated multi-scale framework is established, the macro-scale thermal-chemical and micro-scale stress-strain models are set up to predict the development of the micro residual stress during curing, and the obtained stress field is further employed as the initial boundary conditions in the micromechanical analysis to explore its effect qualitatively and quantitatively. Experimental and analytical methods are taken to verify and validate the current model. Besides, the impacts of different curing cycles on the micro residual stress and out-of-plane tensile strength are also discussed. The evolution of the micro curing residual stress in T700/7901 composites is intuitively revealed, and the results of the micromechanical model show that the out-of-plane tensile strength increases by nearly 14.4% due to the occurrence of the process-induced stress. Both the interfacial damage and matrix plastic deformation are delayed owing to the residual stress. The work builds the connection between the curing process and mechanical responses of unidirectional composites and demonstrates the necessity of considering curing residual stress in designing and evaluating composites.