Wet Strength of Kevlar 29 Ribbon Parachute Fabrics

Abstract

The effect of moisture on the strength of Kevlar 29 ribbon parachute fabrics was investigated. Individual yarn samples and various fabrics were soaked in water for periods of 15-60 min. Yarn strength did not change; however, fabric strength was reduced. The reductions ranged 3-13% depending upon the fabric construction. Additional experiments eliminated factors such as the weaving process, yarn swelling, and increased abrasion in the presence of moisture as possible mechanisms. Other tests demonstrated that increased interyarn friction occurs when moisture is present. These results suggest that the moisture-enhanced friction restrains highly loaded filaments from adjusting their position and relieving stress concentrations. Specific construction parameters governing the amount of strength reduction were not defined in this study. However, it is evident that wet strength should be considered in parachute material selection and design.