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.

Natural fibers are attracting the interest of engineering sectors owing to specific advantages such as lightweight and lower cost as well as an inherent condition of being renewable, biodegradable, recyclable and environmentally correct with respect to CO2 emission. In addition, several natural fibers present mechanical and thermal properties appropriate for engineering applications. The fiber extracted from the stem of the banana plant is nowadays recognized by its mechanical properties. However, some thermal properties of the banana fibers have not yet been fully investigated. The present work investigated, by photoacoustic spectroscopy and photothermal techniques, the thermal diffusivity, specific heat capacity and thermal conductivity of the banana fiber. The results revealed that the banana fibers showed a promising thermal insulation capacity, comparable to those of conventional synthetic insulators.

The fiber extracted from pineapple leaf (PALF) displays relevant mechanical properties that are motivating investigations for possible engineering application as polymer composite reinforcement. As any natural lignocellulosic fiber, the PALF presents non-uniform dimensions and heterogeneous properties with a significant dispersion of values. In fact, a marked variation in the tensile strength has been reported, which represents a problem for the design of a PALF reinforced composite. In several other lignocellulosic fibers, the diameter dimension was found to affect the value of the tensile strength. This work investigated the precise diameter dependence of the PALF tensile strength using the Weibull statistic method. The results showed a mathematical hyperbolic type of inverse correlation between the PALF strength and its diameter, which was found to be similar to that commonly obtained in other lignocellulosic fibers.