Hemp fiber biocomposites and fiberglass composites for structural application : a comparison

High interest towards biocomposite materials is especially due to their design flexibility and sustainable nature. They are nowadays largely employed in many fields of applications such as automotive, buildings, naval, electronic and even aeronautic, especially in substitution of glass fiber-epoxy composites, thanks to their lower costs and lower environmental impact. Although, due mainly to several problems related to natural fibers, which constitute the biocomposites reinforcement, they remain confined to non-structural applications. Based on the similar specific properties of glass fibers and hemp fibers, the aim of this thesis is to compare the mechanical characteristics of a bio composite spar, for small aeronautic structure, to those of a fiberglass-epoxy composite one, and to analyze the several issues related to the manufacture. After a brief study of the two types of woven fabric and of the two types of resins four spars were manufactured by hand lamination and vacuum bag curing, followed by suitable post-curing cycles. Static torsion and bending tests and a bending failure test were carried out. At last, an analysis by means of scanning electron microscopy (SEM) of the composite spars was performed in order to observe the fractured surfaces and fibers, the matrix-fiber adhesion and possible presence of voids in the matrices.