STUDY OF MECHANICAL BEHAVIOR OF NOVEL FIBER METAL LAMINATES

Abstract

FMLs are a class of advanced hybrid materials, constructed by alternately bonding layers of metal with layers of fiber-reinforced polymers, providing the enhanced mechanical properties of all components. The advantages of this composite material include high strength-to-weight ratio, fatigue, and damage resistance, making it well-suited for aircraft construction. However, one of the main challenges related to the FML structures is interfacial delamination, which becomes a reason for early failures. This research investigates the ways to improve the interfacial strength between the composite’s layers by studying: the effect of cellulose nanofibers on the tensile strength and Young’s modulus of polyurethane experimentally; the effect of nanomaterial on the shear strength of single-lap joints – both experimentally and numerically; the effect of mechanical and chemical treatment on the shear strength of single-lap joints; the synergetic effect of CNF and surface treatment on the shear strength. The study reveals that the addition of CNF can significantly enhance the tensile strength of the polymer and the shear strength of the adhesive joints but only up to a certain limit. 1 wt% of CNF increased the tensile strength and Young’s modulus of the polymer by 401% and 66.6% respectively, while for the single-lap joints, the highest shear strength was achieved with 0.5 wt% of CNF giving an 86% increase. It was also investigated that both mechanical and chemical treatment considerably improve the bonding strength in the single-lap joints, and the best result can be achieved by the synergy of chemical treatment and the addition of CNF, which improves the shear strength by 137%. The obtained numerical results for the single-lap shear test from the computer simulation are close to the experimental values and can be used for further investigation of single-lap joints’ mechanical behavior. The findings of this study may provide valuable insights into the development of next-generation FMLs with improved performance and durability.