Effect of Freeze–Thaw Cycling on the Screw Direct Withdrawal Resistance of Beech, Ozigo, and Okoume Plywoods

Abstract

Wood has been used in the construction, furniture, and automotive industries since ancient times. In areas where wood material is used, it is combined with various fasteners. The durability of the products produced using wooden materials depends on the performance of the fasteners. Since wood is a hygroscopic and biodegradable material, various changes occur in its structure when exposed to external weather conditions. Wood materials used especially in the field of construction and urban furniture are exposed to effects such as extreme temperatures, freezing, moisture, or drying depending on the seasons. In this study, the effect of the freeze–thaw cycling (FTC) process on screw direct withdrawal resistance (SDWR) of plywood produced from beech, ozigo, and okoume species was investigated. In this context, the effects of screwing time (before or after), screw orientation (face or edge), the number of cycles (0 to 7) in the FTC process, and plywood type parameters on SDWR were investigated. As a result of the tests, when the mean SDWR values were examined according to the plywood type, the highest values were obtained in beech, ozigo, and okoume plywood, respectively. Considering the screwing time parameter, it was determined that there was no statistically significant difference between the mean SDWR values in other plywood types except beech plywood (p < 0.05). When the screw orientation parameter was examined, screwing in the face direction gave better results than screwing in the edge direction in all plywood types. There was a decrease in the mean SDWR values that was inversely proportional to the increase in the number of cycles in FTC-treated plywood.

Prediction of screw withdrawal resistance for plywood laminated panels and sandwich panels

“…Regarding panels for both laminated faces (sandwich panels), SWSs for PW-MDF-PW and PW-PB-PW were 73.03% and 139.39% greater compared to MDF and PB, respectively. Screws penetrate each of the plywood layers and core layer of MDF/PB in screwing in face orientation, so screw treads held in each layer in the panel, and SWS was enhanced by an increase in the number of layers (Birinci and Kaymakci, 2023). Besides, failure on specimens in the screw withdrawal test occurred on the top-face of the panels, so the top-face laminated specimens had higher SWS compared to those of the bottom face.…”

“…However, SWR increased with the use of reinforcement, but there were no statistical differences to reinforce LVL with either glass-fiber or carbon-fiber. Birinci and Kaymakci (2023) ascribed that external weather conditions negatively affected the SWR of the plywood (PW), and there is no statistically significant difference between screwing samples before and after Freeze-Thaw Cycling.…”