Strengthening of Caucasian Fir and Anatolian Black Pine by using CFRP and investigating the effect of mechanical and microstructural properties on the strengthening process

Abstract

Wood, one of the oldest building materials, continues to thrive alongside other construction materials due to its unique properties. As an anisotropic, hygroscopic material, wood’s mechanical properties vary with direction, and it can lose strength over time due to structural defects, shrinkage cracks, and pest infestations. Increasing the use of wood as a sustainable and economical building material is possible thanks to various strengthening processes. This study evaluates the effectiveness of carbon fibre-reinforced polymers (CFRPs) in strengthening structural timber from Caucasian Fir and Anatolian Black Pine. Samples were subjected to axial compression and four-point bending tests. For each test, nine samples from each tree species were tested. Rather than providing merely an incremental mechanical assessment, this study introduces a novel multi-scale framework. The results established a direct quantitative correlation between specific microstructural architectures and the macroscopic efficiency of different CFRP wrapping orientations, explicitly demonstrating that localised cellular morphology dictates the optimal strengthening mechanism for each distinct wood species.