Study of parameters affecting the strength of yarns

Abstract

Woven fibres and yarns are generally used in the form of a laminate embedded into a matrix. However, these materials are increasingly being used in the pure and the woven form such as fabric for ballistic protection clothing and confinement chambers for jet engines. These applications have created a demand for numerical modelling of the fabrics and more in depth information about the behaviour of fibrous materials and yarns. Manufacturers of yarns usually provide some quasistatic material parameters for the single fibre form of the material. However, this information cannot be scaled up linearly for a yarn consisting of many fibres. Also, the strain rate at which this information is obtained is not in the same order of magnitude as the strain rates observed in ballistic applications.The purpose of this study is to gain an understanding of parameters that affect the strength of yarns. Quasistatic and dynamic strength of various yarns are obtained using hydraulic and Hopkinson bar testing methods respectively and the rate dependency of the failure strength of each yarn is quantified. Weibull models are applied to each set of tests to observe whether the parameters obtained can be used as size independent material properties. The scaling effect will also be studied experimentally in order to observe the effect of specimen size to the failure stress of yarn