QUANTITATIVE ASSESSMENT OF BARELY VISIBLE INDENTATION DAMAGE (BVID) IN CF/EP SANDWICH COMPOSITES USING GUIDED WAVE SIGNALS

摘要

A sandwich structure consists of two strong panels separated by a lightweight core such as honeycomb. The separation increases the moment of inertia with only a slight increase in weight, producing an efficient structure for resisting bending and buckling loads. Composite sandwich structures are applied to primary components in aerospace applications, therefore they are susceptible to incur impact damage which creates a major concern related to structural integrity [1-2]. Low velocity impacts are caused by various sources from bird strikes, dropping tools on parts during manufacturing and servicing or runway debris during takeoff. Such impacts could easily crush the core or create a dent on the surface of the skin [2-3]. The low velocity impact can produce widespread core damage which can significantly reduce the residual strength due to the deterioration in the mechanical properties of both the skins and the core [3]. Those types of impact usually produce hidden damage which is referred to as Barely Visible Indentation (or Impact) Damage (BVID). Structures with existing damage, in operation, may lead to the extension of the damage severity, eventually causing a catastrophic failure [1].