Application of carbon and glass fibre hybrid composites to load bearing orthoses & protheses
Application of carbon and glass fibre hybrid composites to load bearing orthoses and prostheses The aim of this work was to introduce high performance fibre composites into prosthetics and orthotics. Advantages were seen in these materials from their high specific strength and stiffness which could produce lighter and cosmetically more acceptable appliances. Composites of carbon fibre, glass fibre and hybrids of the two were examined to assess their structural suitability. Laminates of different compositions were fabricated from unidirectional fibre tapes using vacuum consolidation. To investigate, relationships between composition and mechanical properties tensile, flexural, shear and impact tests were performed. From these results and from a study of failure mechanisms using high speed photography in conjunction with scanning electron microscopy, suitable materials were identified. To establish optimum fibre orientation for lower limb components" helically wound cylindrical specimens were tested in torsion and compression. These simulated the application and also provided well-defined loading conditions for biased laminates. A resin injection technique used in the prosthetics industry was modified for the manufacture of cylinders and prosthetic components from unidirectional hybrid tapes. Hybrid composite sockets were made for a patient who normally used a conventional GRP extension prosthesis. A socket of this, design successfully completed a cyclic compression test in accordance with Department of Health requirements. To assess the reaction of the patient and the limb fitters, a similar socket was incorporated into a prosthesis by J. E. Hanger & Co. This socket was considerably thinner than GRP sockets which allowed an ankle joint to be included. The patient found this prosthesis light and more comfortable to use than her normal appliances. When it was completed, the patient's request to keep the prosthesis was granted. This work demonstrated that hybrid composites can be used successfully in load bearing prosthetic or orthotic applications.