Plant-derived thermosetting composites

water absorption and mechanical properties retention after weathering

Abstract

In order to widen the application fields of thermosetting composites, this research aims to identify the bioresins and biofibers more resistant to weathering, enabling their use outdoors. Data were collected from experimental scientific research on thermosetting composites made from synthetic or plant-derived matrix with plant or hybrid fibers, and using various molding processes, reinforcement geometries, alignment and treatment of plant fibers and fiber/matrix fractions. The investigation searched for researches that studied the composites tensile and flexural strengths; their water absorption in 24 hours of immersion and until saturation; and their retention of mechanical strength after accelerated or natural aging. The effect of matrix and fiber types and their fractions on these properties was investigated. The results indicate that composites with plant-derived matrix and with hybrid or sisal fibers are those that absorb less water in 24h, and that composites with flax have the lowest water absorption at saturation and the greater retention of tensile strength after aging. In other words, these composites are less prone to weathering and thus have the greatest potential for outdoor use. However, regardless of the fiber type, as its content increases, the retention of flexural strength of composites decreases, limiting their usage in some applications.