Variation of Woven Fabric Length and Thickness with Regain

Abstract

A theory of the hygral expansion of simple woven fabrics is proposed, based on Olofsson's theory of woven fabric struc ture. Hygral expansion is seen as the result of the competing effects of yarn swelling, yarn compression, and yarn curvi linear length extension with regain. Early attempts by the author to reconcile theoretical predictions with experimental data showed that it was necessary to suppose a yarn curvilinear-length expansion with regain in excess of that expected from the straightforward contribution from the fiber longitudinal expansion with regain. Taking into account measured yarn curvilinear expansion, which was found to be of the order of 3-4% dry-to-wet, a fair qualitative agreement of theory and experiment is obtained for unset fabrics. There is disagreement in the case of set fabrics below normal regain, which could be attributed to separation of the cross yarns. The fabrics are set wet and, as the yarns dry out and are affected by hygral "contraction," they could separate.