PSI - Issue 77

Fang Liu et al. / Procedia Structural Integrity 77 (2026) 215–220 F. Liu/ Structural Integrity Procedia 00 (2026) 000–000

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Keywords: Mechanical performance; Prosthetic socket; Finite element analysis; Coefficient of friction; Poisson’s ratio

Nomenclature μ

coefficient of friction

ν

Poisson’s ratio finite-element polyethylene

FE PE

PETG polyethylene terephthalate glycol HCFRPs high performance carbon-fiber-reinforced polymers E Y oung’s modulus σ y yield stress FE finite element μ ₁ initial shear modulus α ₁ nonlinearity parameter D ₁ compressibility parameter

1. Introduction The prosthetic socket constitutes the principal load-transfer interface between the residual limb and the prosthesis, with its comfort and structural integrity being decisive for sustained prosthesis use. Clinical reports indicate that more than half of lower-limb prosthetic socket users experience pain or dissatisfaction (Berke et al., 2010; Dillingham et al., 2001) , with poor fit linked to dermatological complications in over 70% (H. E. J. Meulenbelt et al., 2011) and abandonment rates approaching 60% (H. E. Meulenbelt et al., 2009). These findings underscore the urgent need for socket design strategies that concurrently enhance user comfort and ensure structural safety. Biomechanical interactions at the limb–socket interface are influenced by several factors, among which the interface friction coefficient (μ) and the Poisson’s ratio (ν) of the socket material play major roles. The μ governs shear transfer and stick–slip behaviour at the limb–socket interface. Both abnormally low and excessively high values of μ have been associated with adverse mechanical environments, such as elevated shear or pressure concentrations, which may contribute to discomfort and soft-tissue damage (Dickinson et al., 2017a) . The ν of the socket material is another fundamental parameter that reflects material compressibility and governs lateral deformation under loading. Polymers and composites commonly employed in prosthetic socket fabrication exhibit inherent compressibility, with experimentally reported Poisson’s ratios covering a relatively wide interval (approximately 0. 10–0.49), contingent on factors such as molecular architecture, filler incorporation (Greaves et al., 2011a). Such variability highlights the critical role of ν as a design parameter, since modifications in material selection or formulation can directly alter its magnitude and thereby modulate stress redistribution within the socket wall. Although the independent roles of μ and ν have been investigated in studies of limb–socket biomechanics and material mechanics (Cagle et al., 2018; Matray et al., 2025; Safari, 2020; Steer et al., 2021), prior work has frequently relied on static modelling assumptions or treated these parameters in isolation, limiting systematic parametric evaluation across clinically relevant ranges. As a result, the biomechanical implications of variation in μ for residual limb soft tissue stress and of variation in ν for socket stress distribution remain insufficiently characterised. To address this limitation, the present study establishes a three-dimensional dynamic finite-element (FE) model of the transfemoral socket–limb system, in which μ and ν are independently varied across ranges relevant to clinical application. Three representative socket materials—polyethylene (PE), polyethylene terephthalate glycol (PETG), and high-performance carbon-fiber-reinforced polymers (HCFRPs) — were selected to encompass a broad stiffness spectrum. The model quantifies the influence of μ on the maximum soft -tissue stress in the residual limb and the role of ν in determining the maximum stress within the socket . Through a unified parametric framework, this study provides new biomechanical evidence and design guidelines for optimizing transfemoral socket design to balance user comfort and structural safety.