TRIGGER MECHANISMS IN ENERGY-ABSORBING GLASS CLOTH EPOXY TUBES

A study has been made of chamfer-based trigger mechanisms for use with energy-absorbing glass cloth/epoxy composite tubes. Tubes with external chamfers ranging from 10 to 90° were crushed to different extents and the resulting microstructures were examined microscopically. The mechanical properties of the material were determined and used in analysing the initial stages of the crushing process by finite element modelling. It was found that, for this material, the crushing process was usually initiated by local bending of the chamfered parts of the tubes and by internal cracking. These events gave rise to the generation of wedges of crushed material which were pushed to the inside of the tube wall. The stresses generated at the root of the wedge gave rise to lateral cracks, which caused small rings of material to be sheared off. This sequence of events dominated the initial stages of the crushing process. At a later stage, the mode of crushing changed to one of frond-wedge-frond geometry. © 1990.