Manufacturing and characterization of hemp-reinforced epoxy composites

The adoption of natural-based fibers in place of inorganic reinforcements is an effective approach to reduce the environmental and economic impact of composite materials. In particular, hemp is an attractive solution due to its mechanical, physical, and growing properties. The present article deals with the manufacturing of thermoset hemp-reinforced composite materials. In particular, the investigation moves into the production by resin transfer molding and by resin powder molding with the use of epoxy polymeric material. To describe the effects of the technological cycle onto the characteristic of realized products, different manufacturing parameters have been combined during the braiding of reinforcement and the polymerization of the final composite. Computed tomography, microscopical analysis, and tensile tests have been used to observe the main effects of the manufacturing process and mechanical properties of the materials. Furthermore, elastic moduli of the materials have been estimated by means of modified rule of mixture and Halpin-Tsai models in order to verify their effectiveness in forecasting stiffness of the hemp-reinforced composites in the early design phase. The article extends the existing knowledge base on hemp-reinforced thermoset composites manufactured with different processes. Results also illustrate relations existing between error introduced by calculation models and the intrinsic variability in mechanical properties.