NSM Polyester-Reinforced Albizia chinensis Beams: Flexural Performance Evaluation

This study investigates the flexural performance of Albizia chinensis wood beams strengthened using Near Surface Mounted (NSM) polyester resin under four-point bending tests. The primary objective of this study is to evaluate the enhancement in flexural behavior due to the addition of NSM polyester reinforcement. Three beam configurations were tested: unreinforced (TO), single-groove reinforced (TPSE), and double-groove reinforced (TPR). The strengthening process involved embedding polyester resin into pre-cut grooves on the beam surface, where the resin served as both adhesive and filler for bonding the reinforcement with the wood substrate. The experimental results demonstrate that beams reinforced with NSM polyester exhibit higher load capacity and improved stiffness. Specifically, the TPR specimen achieved an increase in the ultimate load of more than 30% compared with the TO specimen. Furthermore, the use of polyester resin as an infill material in the grooves effectively bonded the reinforcement to the surrounding wood matrix. This not only contributed to improved mechanical performance but also showed promise due to its ease of application and cost-effectiveness. The strain distribution in the reinforced specimens suggested a more favorable deformation profile, especially in TPR. Additionally, cyclic testing on the reinforced beams revealed enhanced resilience against repeated loading, making the reinforcement system suitable for dynamic conditions. The results were validated using a theoretical flexural strength estimation based on section modulus and characteristic strength of Albizia chinensis wood. The findings further confirm the feasibility of using polyester as an effective shear reinforcement in structural timber applications, especially in low-cost rural construction. The study concludes that NSM polyester reinforcement is effective in improving the flexural performance of Albizia chinensis wood beams and offers a practical alternative for timber strengthening in engineering practice.