IMPACT BEHAVIOR OF CELLULAR SOLIDS AND THEIR SANDWICH PANELS

摘要

This paper presents a study of the strength enhancement under impact loading of metallic cellular materials as well as sandwich panels with cellular core. It begins with a review of likely causes responsible for the strength enhancement of cellular materials. A testing method using 60mm diameter Nylon Hopkinson pressure bars is used to investigate the rate sensitivity of various metallic cellular materials. In order to identify the factor responsible for the strength enhancement of those materials, a multiscale analysis is performed on a model structure which is a square tube made of rate insensitive materials. At the macroscopic level, significant enhancement is experimentally observed under impact loading, whereas the crushing mode is nearly the same under both static and impact loading. Numeric simulations and theoretical models give a satisfactory explanation of the role of the lateral inertia. An inversed perforation test on sandwich panels with an instrumented pressure bar is also presented. Such a new testing setup provides piercing force time history measurement, generally inaccessible. Testing results show a notable enhancement of piercing forces, even though the skin aluminum plates and the foam cores are nearly rate insensitive.