THEORETICAL MODELING OF BONDING CHARACTERISTICS AND PERFORMANCE OF WOOD COMPOSITES. PART IV. INTERNAL BOND STRENGTH

摘要

A mechanistic model was developed to predict the internal bond (IB) strength of wood composites. Based on the earlier models reported in this series, the IB model integrates the mechanisms of inter-element contact, resin distribution, and localized bond development and debonding failure. Experimental tests were also conducted, and the results compare favorably with model predictions. It was discovered that a composite product having large horizontal density variations typically realizes less than 50%of the bond strength attainable between its constituent elements. The loss of bonding strength is attributed to the premature debonding of low-density regions, and the subsequent load concentration and failure-acceleration of the higher-density regions.The model predicts IB as a function of product density, wood density, resin content, and element dimensions. The IB improves with an increase of product density, resin content, and element thickness. The relationships are monotonic and nonlinear, resulting from their interactions on the contact development or/and the resin coverage. The relationship between IB and wood density is also nonlinear and dependent upon the product density. Implications of the predictive results on fundamental understanding and optimization of wood composite bonding are discussed.