A Stochastic Simulation of the Failure Process and Ultimate Strength of Blended Continuous Yarns

Abstract

The mechanics of the failure process and ultimate strength of a twisted yarn structure are studied using a newly proposed stochastic model of the failure process. The impor tance of the twist reinforcing mechanism to the strength of a twisted structure with continuous components, the interaction patterns between different component types dur ing yam extension, and the significance of multiple breaks along a component are demonstrated. Building on the three basic concepts of fragmentation and chain-of-sub- bundles, changing lateral constraint between components due to twist and its effect on component strength, and load sharing between broken and still surviving members during yam breakage, a new mechanistic approach is proposed and a stochastic computer model is developed to predict the behavior of blended yams. The approach is similar to that developed earlier by Boyce et al. [3] to study the failure process in woven fabrics. The model acts to predict the strength and fracture behavior of a blended yarn with continuous components. The predicted results are illustrated in comparison with the experiments of Monego et al. [20, 21, 22]. By means of this new model, fundamental features of blended yam behavior are simulated and elucidated, including the strength reinforcing mechanism of twist in a blended yam, the yarn break propagation pattern, and the effect of twist on yam fracture behavior as well as the shape effect of component stress-strain curves. Moreover, the relationship between the strength of a structure and that of its components is also investigated.