Experimental Study on Mechanical Performance of Single-Side Bonded Carbon Fibre-Reinforced Plywood for Wood-Based Structures

In addition to the traditional uses of plywood, such as furniture and construction, it is also widely used in areas that benefit from its special combination of strength and lightness, particularly as a construction material for the production of finishing elements of campervans and yachts. In light of the current need to reduce emissions of climate-damaging gases such as CO2, the use of lightweight construction materials is very important. In recent years, hybrid structures made of carbon fibre-reinforced plastics (CFRPs) and metals have attracted much attention in many industries. In contrast to hybrid metal/carbon fibre composites, research relating to laminates consisting of CFRPs and wood-based materials shows less interest. This article analyses the hybrid laminate resulting from bonding a CFRP panel to plywood in terms of strength and performance using a three-point bending test, a static tensile test and a dynamic analysis. Knowledge of the dynamic characteristics of carbon fibre-reinforced plywood allows for the adoption of such cutting parameters that will help prevent the occurrence of self-excited vibrations in the cutting process. Therefore, in this work, it was decided to determine the effect of using CFRP laminate on both the static and dynamic stiffness of the structure. Most studies in this field concern improving the strength of the structure without analysing the dynamic properties. This article proposes a simple and user-friendly methodology for determining the damping of a sandwich-type system. The results of strength tests were used to determine the modulus of elasticity, modulus of rupture, the position of the neutral axis and the frequency domain characteristics of the laminate obtained. The results show that the use of a CFRP-reinforced plywood panel not only improves the visual aspect but also improves the strength properties of such a hybrid material. In the case of a CFRP-reinforced plywood panel, the value of tensile stresses decreased by sixteen-fold (from 1.95 N/mm2 to 0.12 N/mm2), and the value of compressive stresses decreased by more than seven-fold (from 1.95 N/mm2 to 0.27 N/mm2) compared to unreinforced plywood. Based on the stress occurring at the tensile and compressive sides of the CFRP-reinforced plywood sample surface during a cantilever bending text, it was found that the value of modulus of rupture decreased by three-fold and the value of the modulus of elasticity decreased by more than five-fold compared to the unreinforced plywood sample. A dynamic analysis allowed us to determine that the frequency of natural vibrations of the CFRP-reinforced plywood panel increased by about 33% (from 30 Hz to 40 Hz) compared to the beam made only of plywood.