On the dynamic response of sandwich composites and their core materials

Sandwich composites are being aggressively pursued as structural materials by various defense and commercial industries. These include navy, air force, army, automotive and sporting industries to name a few. In the context of structural load bearing members and absorbing dynamic loads, foam core sandwich composites offer unique advantages over traditional composites. The cellular construction of the foam materials not only provides lightweight capability but also a deformation mechanism that allows efficient absorption of energy. Of particular interest in this study is to investigate the behavior of the foam materials and their sandwiches under high strain rate (HSR) loading which are very much prevalent in their actual applications. A systematic approach has been taken to study the response of PVC foam materials at strain rates ranging from quasi-static to around 2000 S-1. First, room temperature response has been extracted for various density foams, and determined their strain rate sensitivities and failure characteristics. Next, two microstructures in the construction of the core materials, namely linear and cross-linked foams, were considered in the investigation. This study revealed that both the categories of foam had direct dependence on temperatures well below the T. of the base polymer. Consequently, the next phase of the investigation included HSR tests at elevated and sub-ambient temperatures. The study has established that at room temperature (RT), the delamination at the sub-interface zone underneath the actual core-skin interface is the critical mode of failure. This sub-interface is characterized by the separation of the dry and resin-soaked cells near the core-skin interface. Failure modes however changed as the test temperature changed from RT to sub-ambient. (c) 2006 Elsevier Ltd. All rights reserved.