Gypsum/flax reinforced composites with enhanced strength, thermal conductivity, sound absorption and flame resistance

Abstract The development of hybrid composites that combine the advantages of both natural and synthetic fibers has gained momentum in the backdrop of increased focus on environmentally sustainable and economically viable materials. These composites offer the superior mechanical performance of synthetic fibers coupled with the environmental benignity and the low cost of natural fibers. In this respect, biobased renewable materials such as flax fiber, with their excellent mechanical properties, have emerged as potential alternatives to glass fibers for various engineering applications. In the present work, we have developed a hybrid composite composed of glass and flax fibers reinforced with varying proportions of gypsum powder (2–6%) by employing the hand-layup method. Epoxy resin was used as the thermoset matrix and the prepared composites were extensively characterized, and the effect of filler concentration on the mechanical performance, thermal, acoustic, and flame resistance properties of the composite was studied in detail. The prepared gypsum-reinforced glass/flax/epoxy composite demonstrated an improved tensile strength from 273 to 314.2 MPa and a flexural strength increase of 81%, which is greater than the value obtained for the bare composite. Morphological analysis showed efficient intercalation of the gypsum filler into the composite matrix, which resulted in enhanced mechanical performance. Increasing the filler content also significantly enhanced the mechanical performance as well as the thermal and noise absorption capacity by approximately 135%, especially at higher frequencies. Moreover, higher flame resistance was obtained for the composite reinforced with 4% gypsum as indicated by the (V0) rating as per the UL- 94 standard.