Experimental Study on the Bonding Performance Between Larix gmelinii in Northeast China and Carbon Fiber-Reinforced Polymer/Basalt Fiber-Reinforced Polymer Materials

To investigate the bonding performance between Northeast larch (Larix gmelinii) and carbon fiber-reinforced polymer (CFRP) as well as basalt fiber-reinforced polymer (BFRP), this paper systematically analyzes the effects of fiber-reinforced polymer (FRP) type, bonding length, and bonding width on the mechanical behavior of the interface through single shear pull-out tests. A total of 20 FRP-timber specimens were designed for the tests, and their ultimate bearing capacity, failure mode, strain distribution, and load-slip relationship were measured. The results indicate that BFRP exhibits greater ductility, averaging 35.04% higher than CFRP, while CFRP demonstrates significantly higher tensile strength, exceeding BFRP by 83.41%. The failure mode of CFRP specimens primarily involves debonding at the timber-adhesive interface, whereas BFRP specimens mainly exhibit debonding at the FRP-adhesive interface. An increase in bonding width leads to a larger bonding area, resulting in a higher ultimate load capacity. However, due to the limitations of effective bonding length, the ultimate load increases rapidly when bonding length is raised from 50 mm to 100 mm, but further increases in length yield diminish returns in load capacity. Strain distribution analysis reveals that the strain in FRP decreases linearly along the bonding length, with peak strain increasing as bonding width decreases. Based on the experimental data, a predictive model for interfacial debonding load capacity was developed, demonstrating good robustness with an average coefficient of determination (R2) of 0.65. This model provides a reliable theoretical reference for evaluating the ultimate load capacity of FRP-reinforced Northeast larch structures, while also offering essential experimental evidence and theoretical support for FRP reinforcement design in Northeast larch wood structures.