This paper presents a qualitative study on the compatibility of unsaturated polyester resin (UPR) bonding to Sengon wood ( Falcataria moluccana ) in a near ‑ surface mounted (NSM) system . Four configurations were tested: TO (control), TP (groove + UPR), TPR (groove + Ø10 mm threaded steel bar + UPR), and TPSE (TPR + end restraint). Four-point flexural testing was conducted on simply supported beams with a span of L = 900 mm and a load spacing of 400 mm . The evaluation focused on visual observations (crack initiation/development, delamination of the UPR–wood interface, indication of bar slippage) without reporting numerical data. The results indicate that a mixture of UPR + MEKP 1.5% (w/w) with fly ash and sand fillers is able to form good encapsulation and support stress transfer in the TPR configuration ; the crack pattern tends to surround the encapsulation and is not visible. The end restraints in TPSE suppress diagonal shear cracks so that failure remains flexurally dominated . Practical implications include the importance of groove cleanliness/roughness , balanced working viscosity , and curing discipline . These findings provide a basis for further quantitative research (load–deflection curves, MOR/MOE , pull ‑ out , and durability).

Index Terms- Falcataria moluccana, Sengon, Polymer, NSM, Beam