Polymer composites reinforced with natural fibers have been increasingly investigated and applied as engineering materials owing to their economical, technical, societal and environmental advantages. The malva fiber, particularly an important resource in the Amazon region in Brazil, only recently begin to be investigated as possible composite reinforcement for engineering application. However, the mechanical properties of composites reinforced with malva fiber are still unknown. In this paper, the flexural behavior of epoxy matrix composites reinforced with continuous malva fiber was for the first time investigated. Specimens of continuous malva fibers aligned along an epoxy matrix were press-molded. Three-points bending test were performed and the fractured specimens were analyzed by SEM. The results showed a marked improvement in the composites flexural properties with the increase in the amount of reinforced malva fiber. This improvement was found to match the Rule of Mixtures, which revealed the unique potential of malva composites for engineering applications.

The giant bamboo fiber is among the strongest in the Bambusa species with a potential for application as engineering material. Its properties have been evaluated but there is limited information on the impact resistance of epoxy composites incorporated with giant bamboo fibers. Therefore, this study evaluated the Charpy impact energy of epoxy matrix composites reinforced with up to 30 vol% of giant bamboo fibers. Specimens with Charpy configuration were press-molded with continuous and aligned giant bamboo fibers reinforcing a DGEBA-TETA epoxy as the composite matrix. The energy absorbed by the composites was obtained in standard impact tests and the fracture surface of ruptured specimens was analyzed by scanning electron microscopy, SEM. The impact energy was found to increase exponentially with the amount of incorporated fiber. SEM observations revealed the mechanism of crack propagation both in the brittle epoxy matrix and in the fiber interface of the composites.