ON HORIZONTAL DENSITY VARIATION IN RANDOMLY-FORMED SHORT-FIBER WOOD COMPOSITE HOARDS

A mathematical model for characterizing horizontal density variation o f a short-fibre wood composite panel is derived in terms of local poin t density variance V(D), point autocorrelation function eta(Z,lambda,o mega) and variance of density averages between finite sampling zones V (D). The point density variance is the upper-bound of zone density var iance as zone size become infinitely small. Assuming random mat format ion, the model predicts how the horizontal density variation changes w ith fibre dimensions and other processing parameters. The zone density variance V(D) as a monotonically decreasing function of zone size is determined by global panel density, compaction ratio (panel-to-wood de nsity ratio), thickness ratio (panel-to-element thickness ratio), and point-to-point density correlation function which, in turn, is a funct ion of element width and length. According to the model prediction, V( D) is affected by element width, length and zone size in a highly inte ractive manner. While increasing width and length and decreasing zone size generally cause an increase in V(D), the extent to which V(D) cha nges with one parameter depends on the magnitude of others. The predic tive results on how the zonal density variation is affected by the pro cessing parameters are graphically presented and discussed. Copyright (C) 1996 Elsevier Science Limited.