Physical and Mechanical Evaluation of Sisal/Glass Fiber Hybrid Polyester Composites Obtained by the Vacuum Infusion Process (VARTM)

The research interest in developing alternative solutions to replace conventional synthetic fibers with natural fibers in composites is due to the several possible benefits of using these fibers, such as low cost, low density, high specific strength and high availability. The objective of this study was to produce hybrid composites from a commercial ortho-terephthalic unsaturated polyester resin obtained from the recycled PET (polyethylene terephthalate) glycolysis reinforced with sisal/glass fibers obtained by the vacuum infusion process. The composites were produced with 3 layers of fibers, the volume of each layer was fixed, and the amount of resin used was the same. For the results, the relative density decreased up to 23% and the moisture absorption reached up to 10.41%, being possible to observe the influence of the layer arrangement on the results. From the mechanical tests of tensile, flexural and impact strength it was observed that the properties decreased as sisal fibers were added, except in the results of maximum deflection in the flexural test of formulations. From the SEM (scanning electron microscope) analyses showed some defects in the direction of the thickness of all formulations produced, possibly from the process conditions adopted and the moisture present in the sisal fibers, which negatively affected the results of mechanical properties and moisture absorption. According to the results of this study, it was possible to obtain some proposed formulations of hybrid composites, such as the (F1), composed of glass, sisal and glass layers (|GSG), which reached properties close or equivalent to those of the reference composite (F0), composed of glass, glass and glass layers (|GGG) and which showed to be potential alternatives to replace conventional glass fiber composites.

Keywords:
Vacuum infusion; hybrid composites; unsaturated polyester resin; glass fiber; sisal fiber