Effect of High-Frequency Low-Amplitude Impact Loads on Polymeric Composites

Composites are used abundantly in aerospace applications. A major issue facing the aerospace industry is the effect of service exposure on the performance of graphite/epoxy structural components. Detailed studies were performed on the structural integrity of graphite epoxy laminations subjected to high-frequency, low-amplitude impact loads. The material response was evaluated by change in stiffness, residual work, and by permanent set and damping coefficient and other related features. The objective of the study was to evaluate the performance, and thereby assess the suitability of polymeric composites as materials for aerospace models for high-speed wind tunnel testing by simulated trials. The observations indicated that high-frequency, low-load impact improves the stiffness of the graphite-epoxy composite; however, it was associated with a reduction in the damping characteristics. The improvement can be attributed to a change in the modulus of the reinforcement due to strain stiffening.