Cyclic tearing of a woven fabric embedded in a soft matrix

Abstract

A composite of a woven fabric embedded in a soft matrix exhibits the attributes of both constituents. The fabric is strong in tension but flexible in bending. The soft matrix impedes fluid penetration. Applications of such composites include tents, rain coats, and wound closure patches. How such a composite tears under cyclic load remains unclear. Here we embed a woven fabric of ultrahigh molecular weight polyethylene in a soft matrix of thermoplastic polyurethane, and tear each specimen of the composite with cyclic energy release rate of a fixed amplitude, G. Two thresholds are identified, G_a and G_b. When G < G_a, the composite does not tear. When G_a < G < G_b, the composite tears by yarn slip without yarn break, and then tearing arrests after yarns jam. When G_b < G, the composite tears, without arrest, by a combination of yarn slip and yarn break. We then prepare a composite with strengthened fabric-matrix interface, and find that G_a increases but G_b decreases. We interpret these findings in terms of stress deconcentration along the yarns. It is hoped that this study will aid the development of fatigue-resistant composites.