Creep in chipboard. 8. The effect of steady-state moisture content, temperature and level of stressing on the relative creep behaviour and creep modulus of a range of boards

Deflection under 4-point bending of a range of board types was measured for up to six months. Results were obtained under steady-state conditions of stress level (30%, 45%, 60%, 67.5% and 75% of the short term breaking stress), relative humidity (30%, 65% and 90% rh) and temperature (10 degrees C, 20 degrees C and 30 degrees C). These results are presented in terms of relative creep and creep modulus. The relative creep for all board types increased with increasing stress level, increasing relative humidity and increasing temperature. An analysis of variance investigating variations between materials showed significant differences in relative creep. When the relative creep of all materials was compared over all conditions and all stress levels, plywood and waferboard had consistently low relative creep values. High alkaline cured PF chipboard and non-British Standard UF chipboard had consistently high relative creep values. The creep modulus of MUF bonded chipboard decreased with increasing log10 (time) under all conditions. Creep modulus also decreased with increasing stress level