Influence of Water Absorption and Pre-drying Conditions on the Tensile Mechanical Properties of Hybrid Lignocellulosic Fiber/Polyester Composites

It is well known that humidity can deleteriously affect composite mechanical properties. In the present study the tensile properties of hybrid jute/cotton and sisal/cotton fabrics— polyester matrix composites were analyzed as a function of fiber content, immersion time in distilled water and of fabric drying just prior to composite manufacture. The results indicate that, as expected, tensile properties increase with fiber content, and that sisal reinforced composites were slightly more affected by water exposure than jute reinforced ones. This behavior was attributed to the higher affinity of sisal fibers toward water absorption. Fabric drying immediately before their incorporation onto the composites was shown to play an important role on composite mechanical properties. Fabric pre-drying led to composites with lower water absorption and higher overall mechanical properties. These composites also displayed a smaller strain at rupture, evincing better fiber to polymer matrix interaction. The data obtained suggests that water acts as a plasticizer for the systems investigated and that plasticization occurred in the early stages of composite immersion in water.