Wettability of a hybrid PTFE/Kevlar fabrics at micro-, meso-, and macroscales

Abstract

Hybrid PTFE/Kevlar fabric reinforced epoxy composites have widely been used as structural self-lubricating liners. To achieve the best working performance, the Kevlar rich side has to be well impregnated (good wettability), whereas the PTFE rich side must remain dry at the same time. Consequently, it is essential to study the wetting properties of both sides from the microscale (fibre) to the macroscale (fabric) via the mesoscale (tow). After characterization of the wetting properties of hybrid PTFE/Kevlar fabrics at each scale, a revised Cassie-Baxter model was developed, linking the three scales and taking into account the three phases, i.e. air, PTFE and Kevlar. Water contact angles served to characterize the wetting properties at every scale and to validate the predictions. This study aims at providing a better insight into the hierarchical wetting of fibrous materials, both from experimental and theoretical perspectives.