Evaluating the durability performance of wood-based panels by a non-destructive bending test

Abstract

We evaluated the durability of wood-based panels by comparing their dynamic modulus of elasticity (Ed) when subjected to repetitive humid and dry treatments. The panels experienced 1-year and 3-month outdoor exposure periods in Shizuoka City, Japan. As the temperature increased, decrements of Ed retention increased. For the same relative humidity, deterioration of the wood-based panels increased with increasing temperature. The highest modulus of rupture (MOR) retention for all the panels was for the 40 °C treatment. As temperature increased, MOR retention tended to decrease. At the 80 °C treatment, MOR retention for particle board (PB) was less than 10 %. Compared to plywood (PW), retention of mat-formed boards declined. One of reasons is due to the difference of bonding configuration. Bonding point of plywood is plain surface, however, that of mat formed board is small point. Thus, bonding points of board are easily collapsed by the ingress of water. Furthermore, mat-formed boards are likely to spring back by water because they are strongly compressed during hot pressing. Ed retention of all the panels decreased within 2 months. After 2 months, the Ed retention of two types of oriented strandboard (OSB) and PW did not decrease significantly. Ed retention of PB gradually decreased. The deterioration behaviour of the same sample during both humid and dry treatments and the outdoor exposure test could be tracked using the non-destructive bending test. Moreover, although the mechanism of deterioration differed between the humid and dry treatment and outdoor exposure test, Ed and MOR were strongly associated (R 2 = 0.77). These results suggest that it is feasible to estimate MOR from Ed using the non-destructive test.