DESIGN AND ANALYSIS OF A NON-ARTICULATED PROSTHETIC FOOT USING DEVELOPED COMPOSITE MATERIALS

 Prosthetic foot is considered one of the most important parts of prosthetic limbs because it is in direct contact with the ground and supporting the body of amputee. Developing designs and materials of prosthetic feet are very important field so as to improve their characteristics to produce better satisfaction for amputees. In this work, previous designs are studied, and new design foot was modeled depending on Niagara foot design. Three groups of new composite materials are prepared. First group is manufactured from polyethylene as a matrix and chopped carbon fibers. Second group is prepared from blending two different grades of polypropylene (polypropylene grade 575, polypropylene grade 513), Third group is prepared from mixing calcium carbonate with polypropylene. The mechanical tests such as tensile, fatigue and impact tests are achieved for these new suggested materials to study the mechanical properties. For the first group, the results of the tests show that the adding of carbon fiber with 20% volume fraction produced highest ultimate tensile strength and modulus of elasticity. The optimum results of toughness obtained from adding 15% volume fraction of carbon fiber, 28 .57KJ/m  for blend of 15% carbon fiber and 85% high density polyethylene, 30.76 KJ/m blend of 15% carbon fiber and 85% linear low density polyethylene.  For the second group, the results showed that the highest toyghness of 55.74 KJ/m 2   is obtained for the blend of 50% polypropylene grade 575- plus 50% polypropylene grade 513. The results for the third group showed that, when adding calcium carbonate to polypropylene, the material toughness is decreased while the modulus of elasticity is increased. Adding 0.5% calcium carbonate to I   2 2   polypropylene, the material toughness is decreased by 40% and when adding   2% decrease the toughness by 50%.  The Niagara foot and the new design foot are analyzed by finite element method by using ANSYS15 software to compute the equivalent stresses, total deformation and factor of safety. The suitable range of amputees weight was determined and it was in the range of (40-75) Kg for Niagara foot, while for the new suggested foot design, it is in the range of (45-75) Kg.  The total deformation is calculated for toe off phase for both feet design to obtain the dorsiflexion. The results showed that, both feet give
acceptable values of dorsiflexion.  For the calculations of safety factor, the results showed higher safety factor for Niagara foot than the new design foot because of the higher properties of Niagara foots material. The factor of safety for the suggested foot ranged from 1.4 to 2.4 while the results for Niagara foot ranged from 2.2 to 3.87 which means that the obtained results are acceptable according to design principles