Fatigue Performance of Coconut Coir/Groundnut Shell Reinforced Epoxy Composites for Below-the-Ankle Prosthetic Sockets

Abstract

This study investigates the fatigue strength of a coconut coir/groundnut shell reinforced epoxy hybrid composite for potential use in below-the-ankle (Syme’s) prosthetic sockets. The composite material's performance was evaluated by subjecting it to cyclic loading tests at various stress levels (500 MPa, 700 MPa, 1000 MPa, 1300 MPa, and 1600 MPa). The number of cycles to failure was recorded, and the results demonstrate a strong relationship between applied stress and fatigue life. At higher stress levels (1500 MPa and 1600 MPa), the material exhibited superior fatigue strength, with cycle counts of 1491.3 x 10³ and 1731.8 x 10³, respectively. In contrast, at lower stress levels (500 MPa and 400 MPa), the material's fatigue life significantly decreased, with cycles to failure dropping to 497.1 x 10³ and 426.52 x 10³, respectively. These results suggest that the hybrid composite performs optimally under moderate-to-high stresses, making it suitable for prosthetic applications where dynamic loading is typical. The findings are consistent with recent literature on natural fiber composites, which indicate that hybrid reinforcements enhance fatigue resistance compared to single-fiber composites. The study also reveals that the composite material may have limitations under long-term low-stress loading, which could be relevant for day-to-day activities such as standing or walking. These results contribute valuable insights into the potential for natural fiber composites as an eco-friendly and cost-effective alternative to synthetic materials in prosthetic design.