Stress analysis for design optimization of composite toe caps using openFOAM

INTRODUCTION The Portuguese Footwear industry, one of the most important internationalized sectors of the Portuguese economy, has been investing in research and development in order to maintain its reference in the footwear industry [1]. Safety footwear, a particular sector of this industry, fits into personal protective equipment (PPE) category and is intended to protect the user’s feet from hazards (e.g., falling objects) and prevent potential accidents (e.g., slippery floor). Toe caps are one of the most important components in this type of footwear, but the currently available ones have a significant contribution to the total part weight, mainly because they are made of steel due to its high mechanical properties. This limitation has been motivating efforts to replace steel toe caps by polymeric ones, since they are lighter, insulated and insensitive to magnetic fields. Nevertheless, polymeric toe caps require larger volumes when compared with their metallic counterparts, which has a negative impact in aesthetics and design. Therefore, the safety footwear industry needs to develop an easy, fast, low-cost and reliable solution to optimize the toe cap component. This work is part of a PhD project and aims the development of a new composite toe cap design with optimized mechanical behavior. The toe cap design should be defined with the support of the computational modelling open source library, OpenFOAM. In order to accomplish this goal, two different case studies that simulate the laboratory mechanical test conditions were simulated, one regarding compressive behavior up to 15 kN, and another a free-falling weight with an impact energy of 200 J [2]. The solid mechanics toolbox developed by P. Cardiff [3, 4] was the solver selected for modelling purposes. The numerical simulations will be validated with experimental results, helping to identify critical zones in the toecap structure, in order to help shape the design with the minimum possible amount of material.

ACKNOWLEDGEMENT The authors acknowledge the financial support by Portugal 2020, and Fundo Social Europeu (FSE) through Programa Operacional Regional do NORTE (NORTE-08-5369--FSE-000034), developed under the program “IMPULSE - Polímeros e Compósitos: Drivers da inovação tecnológica e da competitividade industrial”.

References [1] APICCAPS - Portuguese Footwear, Components, Leather Goods Manufacturers’ Association, “Statistical Report Portugal: Footwear, Components and Leather Goods,” 2017. [2] Personal protective equipment - Safety footwear, ISO 20345:2011(E), 2011. [3] P. Cardiff, Ž. Tuković, P. de Jaeger, M. Clancy, and A. Ivanković, “A Lagrangian cell-centred finite volume method for metal forming simulation,” Int. J. Numer. Meth. Engng, vol. 109, no. 13, pp. 1777–1803, 2017, doi: 10.1002/nme.5345. [4] P. Cardiff et al., “An open-source finite volume toolbox for solid mechanics and fluid-solid interaction simulations,” arXiv e-prints, arXiv:1808.10736, 2018.