In-situ synchrotron x-ray and micro-computed tomography of nonwoven aramids: Deformation mechanisms

Nonwoven materials have attracted much interest in the industry due to their high surface area, high porosity, and low cost. However due to the complexity of deformation mechanisms in these materials, controlling the mechanical properties has been challenging. Therefore, it is important to establish the fundamental understanding of the relationship between the microstructure and the macroscopic behavior. Motivated by this, mechanical properties and deformation mechanisms of aramid nonwovens as a function of areal weight were reported using several analytical tools. The initial fiber orientation alignment was found significantly different within the nonwoven types according to XRD patterns. Fiber orientation evolution under both monotonic tensile and stress relaxation tests was tracked using in-situ X-ray diffraction. As the strain increased, fiber alignment along the loading direction was observed in all three types of nonwovens. Results suggested that the areal weight is not necessarily a predictor of the mechanical properties of aramid nonwovens as the fiber alignment plays a vital role in the performance of these materials.