Design and Simulation of Prosthetic Feet Manufactured by Continuous Filament Fabrication
Topic(s) : Industrial applications
Co-authors :
Abdel Rahman NEDAL IBRAHIM AL THAHABI (ITALY), Luca MICHELLE MARTULLI , Gennaro ROLLO (ITALY), Milutin KOSTOVIC , Jacopo ROMANÒ , Lorenzo GARAVAGLIA , Andrea SORRENTINO (ITALY), Simone PITTACCIO , Marino LAVORGNA , Emanuele GRUPPIONI , Andrea BERNASCONI (ITALY)Abstract :
Commercially available prosthetic feet have different categories and are prescribed based on the ambulation potential of the amputees [1]. Cost-effective prosthetic feet with limited performance, such as the Solid Ankle Cushioned Heel (SACH) foot, are available for amputees with low ambulation potential [2]. Otherwise, Energy Storage and Return (ESR) feet offer higher comfort for amputees with high ambulation potential thanks to their capacity to return significant elastic energy during walking [2]. ESR feet are often made of laminated composites, enabling a lightweight structure with excellent mechanical properties. However, this makes ESR feet expensive and difficult to customize for the end user.
Modern additive manufacturing technologies, namely Continuous Filament Fabrication (CFF), can potentially offer a cheaper and more versatile approach to making similar composite structures [3]. This work aims to utilize finite element (FE) simulations to enhance the framework for designing CFF 3D-printed ESR feet configured as sandwich composite structures.
Our previously developed stiffness-driven design framework relied on beam FE modeling, allowing an efficient iteration upon numerous ESR foot configurations [4]. However, the current work demonstrated the limited accuracy of beam FEs in predicting the bending stiffness of sandwich structures that have the complex shapes of ESR feet. This is because the core infill is prone to large deformations (see Figure 1a), which are unpredictable using beam FE modeling, as experimental tests and plane stress FE simulations suggested. These deformations also limit the ESR feet' biomechanical performance. Therefore, they were minimized by the replacement of the core infill with Continuous Carbon Fiber-Reinforced (CCFR) filaments in the form of rings, as illustrated in Figure 1b. The effect of the CCFR rings on the accuracy of beam FE modeling in predicting the stiffness of ESR feet was investigated. This was through comparative FE analyses between the plane stress FE modeling approach, which was experimentally validated, and the beam FE modeling approach. These analyses were used to assess the reliability of the beam FE design framework.
Moreover, the potential of topology optimization to improve the structural efficiency of the ESR feet developed was investigated. This is to utilize the design freedom allowed by CFF. Topology optimization was performed considering heel and forefoot loading conditions, and based on the results, the CCFR rings in the core were re-arranged. Plane stress FE simulations were performed to assess the structural efficiency of the ESR feet designs analyzed.
Modern additive manufacturing technologies, namely Continuous Filament Fabrication (CFF), can potentially offer a cheaper and more versatile approach to making similar composite structures [3]. This work aims to utilize finite element (FE) simulations to enhance the framework for designing CFF 3D-printed ESR feet configured as sandwich composite structures.
Our previously developed stiffness-driven design framework relied on beam FE modeling, allowing an efficient iteration upon numerous ESR foot configurations [4]. However, the current work demonstrated the limited accuracy of beam FEs in predicting the bending stiffness of sandwich structures that have the complex shapes of ESR feet. This is because the core infill is prone to large deformations (see Figure 1a), which are unpredictable using beam FE modeling, as experimental tests and plane stress FE simulations suggested. These deformations also limit the ESR feet' biomechanical performance. Therefore, they were minimized by the replacement of the core infill with Continuous Carbon Fiber-Reinforced (CCFR) filaments in the form of rings, as illustrated in Figure 1b. The effect of the CCFR rings on the accuracy of beam FE modeling in predicting the stiffness of ESR feet was investigated. This was through comparative FE analyses between the plane stress FE modeling approach, which was experimentally validated, and the beam FE modeling approach. These analyses were used to assess the reliability of the beam FE design framework.
Moreover, the potential of topology optimization to improve the structural efficiency of the ESR feet developed was investigated. This is to utilize the design freedom allowed by CFF. Topology optimization was performed considering heel and forefoot loading conditions, and based on the results, the CCFR rings in the core were re-arranged. Plane stress FE simulations were performed to assess the structural efficiency of the ESR feet designs analyzed.