Experimental Study on Prestressed Forming of Carbon-Fiber-Reinforced Polymer Composites

Abstract

Advanced composite materials have been widely applied in aerospace structures owing to their low weight, high strength, excellent fatigue resistance, and corrosion resistance. However, during the curing and molding processes of carbon-fiber composites, significant residual stresses are introduced within the components due to factors such as thermal contraction, resin curing shrinkage, and the mismatch in thermal expansion coefficients between the fibers and the matrix. This consequently compromises the performance and reliability of the composites, potentially leading to deformation, warpage, and even cracking, which in severe cases may result in component rejection. This paper aims to investigate the mechanisms by which different forms of prestress influence curing-induced residual stress and strain states, and to analyze their effects on the mechanical properties and microstructural evolution of the materials. In this study, embedded fiber Bragg grating sensors were used to monitor strain evolution during the heating, isothermal curing, and cooling stages of unidirectional carbon-fiber-reinforced polymer laminates subjected to no prestressing, uniaxial through-thickness compressive prestressing, or biaxial prestressing. Tensile tests and scanning electron microscopy were subsequently conducted to evaluate the mechanical response and fracture morphology. The fiber Bragg grating results showed that the strain response varied markedly with the prestressing mode and force level. The findings are expected to provide theoretical guidance and experimental references for mitigating curing-induced residual stresses and improving the molding quality of composite materials.