Fatigue Failure Mechanism and Crack Growth in Foam Core Sandwich Composites Under Flexural Loading

Abstract

The flexural fatigue response of foam core sandwich beams has been investigated. Sandwich panels were manufactured using an innovative coinjection resin transfer molding (CIRTM) process. S2-glass fiber with epoxy resins was used as face sheets over a PVC foam core. Testing was performed in a three-point flexure mode utilizing a newly designed fixture such that the localized indentation damage was minimal. Extensive fatigue data were generated for the S-N diagram and crack growth was monitored. Three distinct damage events were found. The first visible sign of damage initiation was a core-skin debond parallel to the beam axis. This debond propagated slowly along the top interface and eventually kinked into the core as shear crack and then grew in an unstable manner resulting in total specimen collapse.