In the present work, the mechanical performance of novel sandwich composite panels based on 3D-knitted spacer fabrics has been investigated. Composite panels were produced using three different types of spacer fabrics having different structural parameters. The sandwich panels were fabricated based on an unsaturated polyester resin using a modified vacuum-assisted resin transfer molding process which allowed the formation of low-density core structures. The produced sandwich composite panels were characterized for flexural, compressive, and impact properties. The effect of different fabric structural parameters (such as cross-thread density, linear density of yarn used in face and core, and structure of face) on the processability and mechanical behavior of composite panels has been thoroughly investigated. The results showed that the composite panels based on spacer fabrics having lesser cross-thread density and made of coarser yarns performed better with respect to compressive and impact properties, whereas the best flexural properties were obtained in case of spacer fabrics with high cross-thread density and made of finer yarns.

Today, the cost, excellence and availability of raw materials are of principal importance. Due to environmental concerns, a very large number of companies are currently developing manufacturing processes using alternative materials for their crop and in search of new markets for the sub-products of their first-line production. Textile industry is an example of the reality that the industry is living these days. With a significant production of waste fibrous materials, textile companies are now looking for applications where waste materials could be an added-value material. Composites reinforced by fibres are being considered for several uses when high performance is essential. The corrosion resistance, potentially high overall durability, light weight, tailor ability and high specific performance attributes enable the use of composite materials in areas in which the use of conventional material might be constrain due to durability, weight or lack of design flexibility. This paper describes the work that is being done at University of Minho concerning the development of waste fibers reinforced composite materials. Different waste fibers reinforced composite materials have been produced varying the density and the variation in ratio of resin and waste fibers. Waste fibers have been collected within some textile companies and processed in order to individualize the fibers and to allow subsequent processing. Composite panels have been produced by compression moulding technique, through the application of heat and pressure. Panel thicknesses of 5 mm using resin aminoplastic for urea-formaldehyde have been produced. Materials thus obtained have been tested in tensile, bending, compression test. The results obtained are presented and discussed.