ANISOTROPIC ELASTICITY OF ORIENTED POLYETHYLENE MATERIALS

In this paper we compare the elastic anisotropy of three classes of or iented polyethylene-based materials. The material types were a range o f polyethylene/epoxy composites, made in both unidirectional and 0/90 cross-ply forms; polyethylene/polyethylene composites manufactured by the new process of hot compaction, again in both unidirectional and cr oss-ply form; and large-section solid-phase oriented polyethylene prod uced by the die drawing process. The elastic properties of these diffe rent materials were determined and compared by means of an ultrasonic immersion technique. By using the properties of the compacted polyethy lene/polyethylene composites, it was possible to obtain a complete des cription of the elastic properties of the original polyethylene fibre. The measured elastic constants of the polyethylene/epoxy composites w ere then compared with those predicted on the basis of theoretical mod els developed in this laboratory. It was of particular interest that t he modified Brody/Ward model was found to be very satisfactory.