A study has been conducted on the mechanisms of in-situ tensile failure of staple
yarns during uniaxial tensioning, as in a conventional ravel strip test. The yarns were
PET/cotton blends processed on ring, rotor, and airjet spinning systems, and then
woven into plain or twill weave fabrics. Load-extension behaviors of the yarns were
recorded for the in-fabric state as well as for the free state (out-of-fabric), and SEM
comparisons were made of the fractured yarn ends obtained in the two states. When
the tensioned yarns became jammed between cross yarns before straightening, the
fracture ends were abrupt, similar to those observed in near zero gauge length tests of
free-state yarns. However, when fabric structure was such that tensioned yams could
straighten without cross yam jamming, the resulting failure zones were considerably
longer, with a mixture of fiber fracture and slippage similar to that observed in long
gauge length tests of free-state yams. The interaction between yarn properties and
weave geometry had a strong influence on the local disturbance of cloth structure
resulting from isolated yam failure during fabric tensioning. The extent of such disturbance
permitted estimates of the stress recovery length of the failed yam and showed
its dependence on cloth tightness and yarn type.