Force protection using composite sandwich structures

In the recent past, advances have been made in the attempt to utilize composite materials as components in protective structures such as those employed by the Air Force to secure critical military assets. In such applications, where lightweight materials that exhibit large levels of energy absorption and high strength/stiffness characteristics are desirable, composite sandwich constructions offer an attractive solution.In an attempt to evaluate the suitability of certain sandwich structures for use in force protection applications, several sandwich constructions with somewhat novel core materials were identified. A group of thermoplastic core materials have been developed that possess features of both a dense elastic solid and a foam type material. This class of core materials incorporates sloping cell walls, rather than the traditional parallel cell wall structure present in, say, a regular aluminum honeycomb. This feature, along with the increased surface area connectivity present between cells (produced by the forming process used to create the core materials) integrates surrounding cells into what may be described as an enhanced hexagonal single unit cell structure.To develop a preliminary understanding of the response of these enhanced cellular materials to the various loading regimes that could be encountered in a protective structure, a series of static and dynamic tests were conducted at Tyndall Air Force Base. A complete description of the novel core materials, as well as the results of the static and dynamic tests, will be presented in this paper.