Development of a Modified Flat-plate Test Specimen and Fixture for Composite Materials Crush Energy Absorption

Abstract

There are currently no specialized test methods for the characterization of specific energy absorption (SEA) of composite materials. Based on an original concept developed by NASA in the early 1990s, a test method that utilizes a flat plate-like specimen and a modified anti-buckling fixture is presented here that introduces a region of unsupported material in the proximity of the crush front, and allows the specimen to deform freely. A systematic experimental investigation is conducted with two unidirectional tapes to verify the general applicability of the test method to screen candidate material systems, and to isolate the effect of the unsupported distance on the measured SEA values. In general, it is found that there are four failure mechanisms (fragmentation, frond formation, local, and global buckling) that compete as the dominating mode according to the chosen unsupported distance. The specimen and fixture combination presents several limitations, but with a properly selected unsupported distance it could be used to assess the SEA of material and structures whose dominating failure mechanism is frond formation.