Development of bonding methods and energy absorption of sandwich panels for thermoplastic advanced composites

Given their high strength-to-weight and stiffness-to-weight ratios, sandwich composites continue to be considered for automotive applications. Thermoplastic materials, while difficult to bond, have an increased ease of manufacture and may be reprocessed, making them an attractive alternate to thermoset composites. This investigation focused on the evaluation of adhesives and surface treatments for both nylon and polypropylene thermoplastic composite adherends made from TowflexRTM pre-impregnated composite fabric. A manufacturing method was established for thermoplastic plates, which produced an acceptable surface finish without contaminating the bonding surface. Adhesives and surface treatments were evaluated using lap shear (ASTM D 3163) and cleavage (ASTM D 3433) test methods. The most promising adhesive/surface treatment combinations were selected for bonding of sandwich composites with two different core materials: balsa wood and polyurethane foam. Initial sandwich configuration testing consisted of flatwise tensile (ASTM C 297) and core shear (ASTM C 273) test methods. These tests provided insights into the sandwich properties and revealed any incompatibilities between the adhesive and the core. Follow on sandwich configuration evaluation consisted of edgewise compression testing, both statically (ASTM C 364) and dynamically. These tests determined the strength and ability of these sandwiches to absorb energy under two different types of loading.