An Investigation into composite additive manufacturing of dynamic response paediatric prosthetic ankle-foot devices.

Abstract

This PhD research explores the potential of composite additive manufacturing for producing dynamic response paediatric ankle-foot prosthetics. It addresses challenges faced by children with lower-limb absence, particularly in accessing prosthetics that support active lifestyles and sports participation. A systematic literature review identified major barriers, including the high cost and limited availability of advanced prosthetic devices. Technological limitations were also highlighted, with many existing prosthetics lacking sufficient energy return and durability for high-impact activities, leading to discomfort and reduced performance. To evaluate the feasibility of composite additive manufacturing in this context, the research investigated the tensile strength, repeatability, and precision of additive manufacturing carbon fibre materials. A parametric study examined how different printing parameters, such as fibre layers, layer distribution, wall layers, and fill patterns, affect mechanical performance. Results showed that increasing fibre reinforcement significantly improved stiffness and energy return, key characteristics for dynamic response prosthetics. Logarithmic equations were developed to predict these mechanical properties, providing a tool for optimising prosthetic designs based on specific user needs. In the final phase, an Ossur Vari-Flex Junior prosthetic foot was used as a benchmark to produce and test an additively manufactured equivalent. The additively manufactured prosthetic was assessed against American Orthotic Prosthetic Association (AOPA) classification standards. Findings confirmed that composite additive manufacturing can produce paediatric prosthetic feet that meet dynamic response criteria, demonstrating its potential as a viable alternative to traditional manufacturing. This PhD makes an original contribution to knowledge by advancing the understanding and application of composite additive manufacturing for paediatric prosthetic design and manufacture. It establishes a validated predictive modelling framework that enables precise control over mechanical properties, stiffness and energy efficiency, based on key printing parameters. The research demonstrates that additive manufacturing can produce dynamic response prosthetic feet, meeting established classification thresholds. This work paves the way for cost-effective, repeatable, and customisable prosthetic solutions, significantly enhancing accessibility for children with lower-limb absence.