INVESTIGATION OF THE EFFECT OF EXTREME TEMPERATURE ON SCREW DIRECT WITHDRAWAL RESISTANCE OF WOOD PLASTIC COMPOSITE DECKING PROFILES

In this study, the effects of extreme temperatures on screw direct withdrawal resistance (SDWR) of wood plastic composite (WPC) decking profiles were systematically investigated. Commercially produced WPC decking profiles were tested at different temperature levels (-40°C, -20°C, 0°C, room temperature, +40°C and +60°C); their effects on SDWR were evaluated by controlling parameters such as screw diameter (3.0 mm and 3.5 mm) and pilot hole diameter (60%, 70% and 85%). Additionally, the relationships between Shore D hardness and SDWR measured at each temperature level were revealed through statistical analyses. The results show that as the temperature increases, Shore D hardness decreases and accordingly, significant decreases occur in SDWR. The highest SDWR was obtained at -40°C temperature, 60% pilot hole ratio and 3.5 mm screw diameter combination. This highlights the influence of material hardness and screw-material interaction on joint performance. According to Pearson correlation analysis, a strong and statistically significant (r=0.939, p=0.0055) positive relationship was determined between Shore D hardness and SDWR.