Effects of Load Level, Core Density, and Shelling Ratio on Creep Behavior of Hardboard Composites

Sustained load bending tests were conducted on large size 3/4-inch-thick, 12-by 39-inch red oak veneered-hardboard composites, hardboards, and red oak lumber. A greater initial elastic deflection generally resulted in a greater total creep and irrecoverable creep deflections. Creep deflections of all composite panels were affected by the load level, core density, and shelling ratio in this study. The red oak lumber exhibited the most creep resistance. However, the composite panel with a shelling ratio of 0.262 was nearly as resistant to creep as red oak lumber. Creep deflections of all composite panels were very well described by a power-law function, based on two separate test models of 2 to 10 min and 10 to 100 min. The extrapolation of log-log regression for the approximation of creep appeared to give reasonable values for up to three weeks. Three multivariable regression models were developed to predict the initial, total, and irrecoverable creep deflections as a function of shelling ratio, load level, and hardboard core density. Their R2 values were 0.96, 0.87, and 0.85, respectively