Abstract
A strain analysis of the foams used as cosmeses for artificial limbs was conducted. It was found that on flexion of an artificial limb strain occurred in the knee region. The mechanical properties of cosmeses materials suggested that the foams would not fail at the strain levels measured when undamaged. However, when the foam became cracked the properties of the foams were reduced to a level that would make failure likely to occur when the cracks reached critical lengths. The failure mechanism of the foam coverings was established via the use of a test rig, designed and built to simulate the interaction between the artificial limb patella piece and the foam. Foam samples were tested both with and without protective elastic netting. The primary cause of failure was found to be wear induced cracking. It was recommended that the design of the patella piece should be changed so as to be less damaging, and that netting should be used for all foams. Silicone foam materials were formulated and investigated for their suitability as a cosmesis foam. Silicone foam samples were tested on the fatigue test rig. Skinned silicone foams with netting had lifetimes three times that of any cosmesis foam tested in a condition currently used in production procedure, and 35% longer than any foam tested in any condition. It was found from leg measurement studies that there was a general leg shape for males and females. Details of leg shapes were transferred to a C.A.D. system. A match from the C.A.D. system for a single amputee's limb can be found. The accuracy of matching is at worst 5%. The current accuracy of matching is generally 15%. The information from the C.A.D. system can be used either to produce moulds for a cosmesis moulding system, or be used in conjunction with a C.N.C. lathe for the direct cutting of cosmeses.