Development of a variable stiffness locally adjustable and repairable low-cost energy storage and return carbon fiber prosthetic foot: A feasibility study

Joshua Scott Bowen, University of Texas at El Paso

Abstract

Background: Energy storage and return (ESAR) prosthetic feet were developed to improve the mobility and function of lower-limb amputees. Amputees in the Developing World amputees lack this technology. Most current Developing World prosthetic solutions do not adequately address the needs of active amputees and were not designed to pass international standard tests. Developing a low-cost, repairable, adjustable, energy storage and return prosthetic foot would close this technological gap and improve the mobility and function of active amputees. The goal of this research is to determine the feasibility of fabricating a low-cost, adjustable, ESAR, repairable prosthetic foot manufactured from carbon fiber using methods and techniques that could be replicated in the Developing World and meet international test standards. ^ Methods: Carbon Fiber plies were hand laid into compression molds to construct the prototype prosthetic components. Static test proof loads of 2065 N and ultimate loads of 3098 N were applied to the toe and heel sections of the prosthesis. Cyclic loads of 1158 N and 1173 N were applied to the toe and heel, respectively. Three unilateral amputees performed walking trials to collect gait parameters and quantitatively and qualitatively assess the prototype prosthetic foot. ^ Results: Less than $100 of carbon fiber was used to construct the prosthesis. Three nested toe layers and one heel layer with an overload spring withstood static loads with no visual damage. Stiffness could be altered by varying layer stiffness and exchanging layers. Heel components withstood 1,000,000 fatigue cycles with no visual damage. Toe components withstood 150,000 fatigue cycles before delamination caused stiffness to be reduced. Toe components were replaced at 450,000 cycles. Hysteresis measurements showed the Prototype Prosthetic foot’s toe returned 5% less energy than the targeted value and the heel returned 31% less energy than the targeted value. Experimental test subjects maintained temporal gait parameters within 10% of their standard prosthetic feet. Subjects’ braking and propulsive energies from their amputated leg decreased greatly compared to their standard prosthetic foot. Subjects’ qualitative assessments showed difficult transitions from heel strike to toe-off, an increased walking effort, and a need to improve energy return. ^ Conclusion: The study demonstrated the feasibility of fabricating a low-cost, adjustable, ESAR, repairable prosthetic foot manufactured from carbon fiber using methods and techniques that could be replicated in the Developing World and meet international test standards. Future work should focus on improving energy storage and return properties, increasing fatigue life, and conduct field tests.^

Subject Area

Mechanical engineering

Recommended Citation

Bowen, Joshua Scott, "Development of a variable stiffness locally adjustable and repairable low-cost energy storage and return carbon fiber prosthetic foot: A feasibility study" (2014). ETD Collection for University of Texas, El Paso. AAI10118134.
http://digitalcommons.utep.edu/dissertations/AAI10118134

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