Design and Development of a Test Fixture and Method for Investigation of Impact During Pre-Stressed Compression

Abstract

As composites become more integrated into large structures and vehicles, there is a need to design for laminate failure associated with realistic combined loading scenarios. Because a structural composite is typically brittle, impact damage has been extensively studied and residual strength has been evaluated post impact damage. Few studies have been conducted to determine the effects of pre-stressing a composite during impact. In the case of in-plane compression during impact, it has been found that there is a synergistic effect which causes more damage than occurs with a standard compression-after-impact (CAI) test. When compressive pre-stress greater than 70 MPa was applied to 150mm×100mm ×5.4mm glass fiber/vinyl ester laminates, an impact initiated shear crack (IISC) developed perpendicular to the applied load leading to failure. To accommodate designers concerned with compressively loaded composite structures that may endure an impact event, a test method has been established to conduct compression during impact (CDI) testing. This paper has reported the design, construction, and implementation of an innovative test fixture that enables investigation of failure mechanisms in the CDI test mode.