Effect of high-frequency low-amplitude impact loads on polymeric composites

Composites are used abundantly in aerospace applications. A major Issue fac ing the aerospace industry is the effect of service exposure on the perform ance of graphite/epoxy structural components. Detailed studies were perform ed on the structural integrity of graphite epoxy laminations subjected to h igh-frequency, low-amplitude impact loads. The material response was evalua ted 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 c omposites as materials for aerospace models for high-speed wind tunnel test ing by simulated trials. The observations indicated that high-frequency, lo w-load impact improves the stiffness of the graphite-epoxy composite; howev er, it was associated with it reduction in the damping characteristics. The improvement can be attributed to a change in the modulus of the reinforcem ent due to strain stiffening.