Prediction and verification strength in APC-2 composite laminates at elevated temperature

Abstract

► We determined the strengths of APC-2 composite laminates with central holes. ► We combined the modified PSC model with the equation of thermal degradation. ► We predicted the tensile strength of notched APC-2 composite laminates. ► The predictions were in good agreement. ► The characteristic length that varied with the environmental conditions. The residual strength of notched AS-4/Polyetheretherketone (PEEK) composite (APC-2) laminates with a central hole at elevated temperature was systematically investigated by both analytical and empirical methods. First, [0/±45/90] 2s quasi-isotropic panels were fabricated and cut into samples. A circular hole with one of five diameters was drilled in the center of each sample. The samples were subjected to quasi-static tensile tests at elevated temperatures to measure their mechanical properties – tensile strength and longitudinal stiffness. Stress concentration and high temperature were found to remarkably affect the residual strength of composite. Point stress criterion (PSC) above was found to be unsatisfactory in predicting the residual strength. A modified point stress criterion combined with the equation of thermal degradation was able to predict the characteristic length at elevated temperature. The residual strengths predicted by the extended modified PSC model were in very close agreement with the empirical data.