Environmental aging effects on high-performance biocomposites reinforced by sisal fibers

Among the innovative materials, an important role is played by the so-called biocomposites, generally made by an eco-friendly matrix reinforced with natural fibers. Unfortunately, due to the degradability of the green matrixes as well as to hydrophilicity of the natural fibers, the resistance of such innovative materials to the environmental agents is, in general, relativity low, and it can significantly limit their use in outdoor conditions. To contribute to the knowledge of the effects of the leading environmental agents on the mechanical properties of high-performance biocomposites made of a green epoxy matrix reinforced by agave fibers, a systematic experimental testing campaign has been carried out by considering three types of biocomposite laminates (unidirectional, cross-ply and quasi-isotropic with a V-f = 70%). In detail, the different effects of aging on matrix and reinforcement have been highlighted by also considering samples consisting of simple epoxy matrix alone. The usual outdoor operating conditions associated with frequent exposure to sunlight (temperature and UV cycles) and humidity have been reproduced by subjecting the biocomposites to an accelerated aging process. Successive tensile and delamination tests have shown that aging leads to significant mechanical properties reductions, ranging from about 40% (tensile) to about 70% (delamination). A systematic analysis of the experimental results has allowed to develop reliable models that can be used to predict the degradation affecting the mechanical properties when these biocomposites are subjected to the actual aging related to the outdoor service conditions.