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Sandwich structures are comprised of two external faces/skins (usually made of synthetic fiber/resin) and a core, being lightweight and with high stiffness. These structures when based on a foam core are commonly processed using liquid molding techniques. In this study, the light resin transfer molding process is used to inject the polymeric resin (vinyl ester) into the porous cavity between the impermeable core and the mold walls. The main goal of the present work is to study the effect of different types of cores (polyvinyl chloride (PVC) and polyethylene terephthalate) and faces (glass fiber cloths or mats) on the mechanical characteristics of the sandwich structures. Specimens were subjected to flexural, flatwise and edgewise compression, and Shore-D hardness testing. General comparison between the different core materials indicated higher flatwise compressive, flatwise tensile and shear strength of the PVC. However, the effect of the core on the properties of the sandwich structure, e.g. flatwise compressive and edgewise compressive strength, was much less evident.

Resin Transfer Molding (RTM) is a manufacturing process in which a

The use of composite structures is ever-increasing due to the need of lightweight materials, and the combination of different reinforcements in a single matrix expands even further the range of processing and final characteristics compared to the use of a single-fiber type. This work investigates the effect of hybridization on in-plane permeability and mechanical properties of R-glass/aramid/epoxy composites manufactured by vacuum infusion. Five different fiber layups were studied, pure aramid, pure R-glass and three hybrids. The inclusion of R-glass fabrics increased permeability compared to aramid, and a synergistic effect was identified, i.e., one of the hybrids presented higher values than both single-fiber stacks. Inclusion of R-glass fabrics leads to greater strength and stiffness in tensile and flexural tests. The hybrids reached an increase of up to 50% in tensile modulus, and also higher compressive, flexural and short-beam strengths. In all, the results have shown that hybridization or aramid composites with R-glass may lead to enhanced processability by vacuum infusion and allow a range of improved mechanical properties, being an alternative in expanding the range of applications for rigid aramid composites.

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