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Influence of leather stretching to gain area yield on its stress‐relaxation behavior
Author(s) -
Manich A. M.,
de Castellar M. D.,
González Berania,
Ussman M. H.,
Marsal A.
Publication year - 2006
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.25188
Subject(s) - stress relaxation , materials science , relaxation (psychology) , composite material , stress (linguistics) , hardening (computing) , yield (engineering) , residual stress , creep , psychology , social psychology , linguistics , philosophy , layer (electronics)
Four bovine leathers subjected to five stretching procedures in water at different temperatures between 60 and 80°C and drawing ratios between 1.20 and 1.40 were analyzed to demonstrate the suitability of the generalized Maxwell model to fit the different stress‐relaxation processes related to the structural hierarchy of leather. This consists of a set of three Maxwell units connected in parallel to represent the high‐rate, the medium‐rate, and the low‐rate stress‐relaxation processes, and a Hookean spring in parallel to represent the residual stress at the equilibrium. The high‐rate, the medium‐rate and the low‐rate relaxation times were approximately of 0.6, 10, and 200 s, respectively. Stretching of leather under different conditions to gain area yield in addition to a reduction in thickness also produces a decrease in leather density but not always induce hardening of leather. Leather stretching increases the initial stress when leather is strained 20% for stress‐relaxation tests. The effect of stretching on the residual stress depends on the level of stretching. The hardening effect of stretching measured by relative softness showed a good relationship with the medium‐rate relaxed stress. The harder the stretched leather the higher the decrease in the medium‐rate relaxed stress. Softness also showed a good relationship with the low‐rate relaxation time. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 6000–6008, 2006