Assessment of Adhesion in Woven Fabric-Reinforced Laminates (FRLs) Using Novel Yarn Pullout in Laminate Test

Abstract

Fiber-reinforced laminates with flexibility (FRLs) are becoming increasingly crucial across diverse sectors due to their adaptability and outstanding mechanical attributes. Their ability to deliver high performance relative to their weight makes them indispensable in lighter-than-air (LTA) applications, such as aerostats, inflatable antennas, surge bladders, gas storage balloons, life rafts, and other related uses. This research delved into employing woven fabrics as the reinforcement material and explored how their specific parameters, like fiber type, fabric count (warp thread density × weft thread density), fabric areal density, and fabric cover influence the bonding and mechanical properties of laminates. A thorough analysis encompassing standard T-peel (ASTM standard D1876) and a newly proposed yarn pullout in laminate test were conducted on laminates fabricated with various woven reinforcements, each with its unique specifications. The T-peel test was utilized to gauge the adhesive strength between FRL components, offering crucial insights into interfacial bonding within the laminates. Nevertheless, challenges exist with the T-peel test, including instances where the adherents lack the strength to withstand rupture, resulting in unsuccessful peel propagation and numerous outliers that necessitate costly additional trials. Thus, our research group introduced a novel yarn pullout in laminate test to accurately assess adhesion in FRLs. This study uncovered correlations between both adhesion tests (T-peel and yarn pullout in laminate), indicating that the innovative yarn pullout in laminate test could effectively substitute for characterizing adhesion in FRLs. Furthermore, the findings unveiled a complex relationship between woven fabric specifications and laminate properties. We noted that variations in fiber type, yarn linear density, and adhesive type significantly impacted adhesion strength. For instance, Kevlar exhibited markedly superior adhesion compared to Ultra-High Molecular Weight Polyethylene (UHMWPE) when paired with Thermoplastic Polyurethane (TPU) adhesive, whereas UHMWPE demonstrated better adhesion with Ethylene Vinyl Acetate (EVA). Moreover, the adhesion quality lessened as fabric count increased for the same adhesive quantity. These discoveries carry practical implications for material selection and design across industries, from automotive to aerospace, offering avenues to enhance FRL performance.