SANTOS, D. G.; SANTOS, Danielton Gomes dos.
Resumo:
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
D 256), and others samples with dimensions of 20 x 20 x 3 mm3 and 20 x 20 x 6 mm3 for water
sorption tests (ASTM D 570). 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.