A novel wood-strand composite laminate using small-diameter timber

by 1978- Weight, Shilo Willis

by Shilo Willis Weight, MS Washington State University May 2007 Chair: Vikram Yadama Our forest resources are changing due to fire prevention and depletion of increasing quantities of old growth forest. Applications for small-diameter juvenile timber, especially for low-value species such as ponderosa pine are needed. In this study, a novel thin wood strand composite 3.2 mm thick is introduced as a veneer substitute. In the first part of the study, optimization was performed for three processing parameters: PF resin content (3-6%), platen temperature (145-160º C), and strand length to thickness (L/t) aspect ratio (315, 430, and 750). Testing of the optimized formulation, consisting of 5.5% resin, platen temperature of 152º C, and a strand L/t aspect ratio of 430, yielded mean MOE and MOR values of 10.2 GPa and 79.1 MPa respectively. These values were approximately 2 to 2.5 times higher than the parent small-diameter ponderosa pine lumber. In the next phase of this study, Young’s modulus, Poisson’s ratio, and shear modulus of thin plies were obtained for use in predicting laminate properties using classical lamination theory (CLT). Three laminate configurations formed of thin plies and one oriented strand composite (OSC) were then tested to compare mechanical and physical properties. Results showed that laminated strand ply (LSP) composites had iv more uniform density throughout the ply, less thickness swell, and lower water absorption than the traditionally formed OSC. Elastic and strength properties of LSP composites compare favorably with plywood and LVL composites made of veneer, and exceeded those of OSB and particleboard. It was shown that the CLT model was useful in engineering composite lay-ups to give an approximation of LSP composites properties. Some of the observed advantages to using thin strand composites are high strength and stiffness, less variation in vertical and horizontal density distributions, continuous press manufacture, and utilization of low value small-diameter timber to form a value-added product. . v