Properties of Structural Sandwich Core Materials: Hand Lay-up vs. Vacuum-Infusion Processing

摘要

Vacuum-Assisted Resin Transfer Molding, or "vacuum- infusion," has grown significantly in popularity over the past decade or two in part due to advantages of a significantly reduced environmental footprint, lower weight per unit area, and debatably lower manufactured part cost. Suppliers of reinforcements and resins have undertaken considerable research on the physical properties of "single-skin" composites produced by vacuum-infusion in relation to contact molding. However, little has been presented on similar comparisons for structural sandwich composites. Thus, the objective of this study was to compare the properties of identical laminate builds comprising two plies of 1808 E-glass fabric on each side of nominal 0.5" (12.5 mm) thick core materials, produced by both vacuum-infusion and hand lay-up processing. Core materials investigated included pre-coated/decay-resistant end-grain balsa, two densities and two suppliers of cross-linked PVC foams, two extruded PET foam variants, an extruded polypropylene honeycomb core, one density of an SAN foam, three densities of polyurethane foam, and a special core comprised of an assembly of low-density polyurethane foam planks filament wound with E-glass rovings, bound on both sides with scrim. All core materials with the exception of the last two types were scrimmed and had either knife-cut or saw-cut kerfs. The polyurethane foam cores were not scrimmed, but instead were double-cut. Characterizations included initial core density, laminated weight per unit area, average thickness, and strength and stiffness for both flexural as well as "flat-wise" tensile testing. Significant among the findings of this study were a substantial reduction in overall panel thickness and areal weight, subtle differences in flexural strength, a significantly lower flexural stiffness, slightly greater flat-wise tensile strength, and significantly greater flat-wise tensile moduli, for vacuum-infusion processing in comparison to hand lay-up.