Common Local Instabilities of Composite Sandwich Structures with Honeycomb Cores

Sandwich structures are ideal structures for very light weight and stiff components for applications in aerospace vehicles. In common transport aircraft sandwich structures are often used for secondary parts like flaps, fairings, and interior equipment. In helicopter industry, also primary structural components are made from sandwich material. When designing sandwich structures, special attention has to be paid to special sandwich failure modes. Due to the very light and relatively weak sandwich core, local and global instability phenomena become very important. Common light weight sandwich structures loaded in compression or bending fail in the compression loaded facing locally due to face sheet wrinkling or the whole sandwich fails more or less globally by sandwich shear crimping. Both failure modes are addressed in this paper. Comparisons of coupon test results with analytical approaches are done and some recommendations for designing sandwich structures are given.