Estudo termo-hídrico e caracterização mecânica de compósitos de matriz polimérica reforçados com fibra vegetal: simulação 3D e experimentação.

Abstract

Vegetables fibers are highly hygroscopic, and when used as reinforcement in polymeric composites can affect the mechanical properties of the composite. This study was carried out to evaluate the mechanical characterization and water sorption of polymeric matrix composites reinforced with sisal fibers in the dry and water saturated conditions at different temperatures (25, 50, 70°C). It was used an unsaturated polyester resin matrix (Resapol 10-316). Samples were made in rectangular cross section for tensile test (ASTM D 3039) and impact test (ASTM D256), and others samples with dimensions of 20 x 20 x 3 mm³ and 20 x 20 x 6 mm³ for water sorption tests (ASTM D570). With the aim of analyzing the tensile strength and the impact of the composite (dry conditions), samples were fabricated with fiber content (by weight): 20; 25.5; 37; 44.6 and 50%. The composites made with 44.6% sisal fibers presented the best mechanical properties, and new samples were subjected to water baths at different temperatures (25, 50 and 70°C), and their mechanical properties evaluated in the saturated condition. A mathematical model (Fick's Law) and its analytical solution were developed to predict the distribution of moisture inside the composite throughout the process and to estimate the mass diffusion coefficient. Results of the average moisture content and distribution of the moisture content in the solid are presented and analyzed. The results exhibited how higher water bath temperature the sample takes less time to reach maximum saturation, lowest value of the mechanical properties of tensile and impact, and larger is the mass diffusion coefficient inside the solid. The studies also indicated that the samples with larger area/volume ratio presented higher diffusion rates.