Mechanical Parameters of Leather in Relation to Technological Processing of the Footwear Uppers

Abstract

This paper aimed to define two critical mechanical properties of leather—Young’s modulus and Poisson ratio—essential to the virtual simulation of the behaviour of the footwear uppers against the manufacturing operations of stitching and perforating. The following technological aspects were considered to analyse the materials from manufacturing conditions point of view: the number of layers (one layer and two layers), the nature of the materials used for uppers subgroups (calfskin-outer upper, sheep leather-lining, polyester knitted fabric-lining), the overlapping width in the stitching area, the number of parallel stitches (single stitch and double stitch), the punching interval and the type of perforations (simple and with eyelets), resulting in nine kinds of samples. Furthermore, the elasticity (Young’s modulus) and lateral contraction (Poisson’s ratio) were calculated during the tensile strength analysis performed on the SATRA STM 466 equipment. Both mechanical parameters are essential to simulate the behaviour of the virtual footwear prototypes in various conditions.

Innovative chitin-glucan based material obtained from mycelium of wood decay fungal strains

“…A comparison with the mechanical properties presented by similar materials as animal leather is quite difficult, considering the wide variability of thickness and properties presented by animal skins from different sources. However, in general terms, it can be observed that most of the tested materials present comparable strength, stiffness and ultimate elongation as animal skin, for cow/calf leather, reported values are in the range of 3–13 MPa for strength, 50–100 MPa for tensile modulus and 10–30 % for break elongation [ 45 , 46 ]. The data are reported as average ± 1 standard deviation, repetitions for each specimen is 5.…”

Examining the Impact of Stitch Density, Thread Size, and Direction on the Seam Strength of Cow Upper Leather

“…Depending on the target of the experiments, different S/N ratios can be selected. Under these different selections, S/N ratios quantify how the variation in the response happened relative to the target value [7]. Three different S/N characteristic formulations (conditions) are present in the following equations [13].…”

“…Different thread sizes may affect the tensile strength and overall integrity of the seam. Additionally, stitching direction, whether parallel or perpendicular to the leather grain, can influence the seam's resistance to stress and deformation [7]. The stitching direction, whether parallel or perpendicular to the grain of the leather, can influence seam strength.…”

The Influence of Materials on Footwear Behaviour: A Finite Element Simulation Study

“…The tensile curves (Figure 3) of materials used for footwear upper exhibit a nuanced response with characteristics encompassing non-elastic, elastic, and plastic-type behaviours [38]. Consequently, the tensile curve can be divided into distinct regions.…”