Chun Won Kang

Sound absorption capability and mechanical properties of a composite rice hull and sawdust board

Rice hull–sawdust composite boards were manufactured for sound-absorbing boards in construction. The manufacturing parameters were target density (400, 500, 600, and 700xa0kg/m3) and rice hull content as percent weight of rice hull/sawdust/phenol resin (10/80/10, 20/70/10, 30/60/10, and 40/50/10). Commercial gypsum board and fiberboard were also used as comparative sound-absorbing materials. The average modulus of rupture (MOR) of the board with a density of 700xa0kg/m3 and rice hull mixing ratio of 10% was 8.6xa0MPa, and that of the board with a 400xa0kg/m3 board density and a rice hull mixing ratio of 40% was 2.2xa0MPa. The MOR increased with increasing board density or decreasing rice hull mixing ratio. The sound absorption coefficients of some boards (400xa0kg/m3 and 10%, 500xa0kg/m3 and 30%, and 500xa0kg/m3 and 40%) were better than those of the commercial 11-mm-thick gypsum board. Thus, it is concluded that rice hull–sawdust composite boards may be implemented as sound-absorbing barriers in construction due to their high sound absorption coefficients.

Effect of the knife-incising pretreatment on the surface checks occurrence of red pine heavy timber after drying

The aim of this study was to investigate the effect of the knife-incising pretreatment on the surface checks occurrence of red pine heavy timber after drying. The effect of knife-incising was evaluated by comparison with surface checks which occurred in the control and kerfed material. The results revealed that the knife-incising treatment was effective compared with control in the prevention of surface checks, and the effect is similar to that of the kerfing treatment. In addition, the combination of incising and kerfing was most effective in preventing surface checks.