Predicting the short-term properties of chipboard using composite theory

Summary

The applicability of models for describing the short-term properties of chipboard were investigated using the results from experiments conducted on samples of a laboratory-made chipboard (comprised of Scots pine chips and urea formaldehyde resin), and sections of urea formaldehyde and Scots pine strips.

The “rule of mixtures” equations, modified for short fibre composites, were employed to predict the strength and stiffness of chipboard. They were found to provide a good estimate of both the chipboard strength and modulus of elasticity, with the assumptions being made that the chips were aligned parallel to the direction of applied stress and that the chips could be treated as having cylindrical geometry.

The results of this investigation revealed that chipboard is a highly unusual material. Compared to conventional fibre-reinforced composites, chipboard has a very high volume fraction of fibres, and the similar moduli of elasticity of the fibres and matrix can result in the concentration of stress in the matrix rather than in the fibres. However, these factors did not prevent the assessment and development of appropriate short fibre composite models to predict the strength and stiffness of chipboard.