Vikram Yadama

Manufacture of laminated strand veneer (LSV) composite. Part 1: Optimization and characterization of thin strand veneers.

Abstract The forest resources are changing due to fire prevention and depletion of old growth forest. Applications for small-diameter juvenile timber, especially for low-value species, such as ponderosa pine (Pinus ponderosa) are needed. In this study, a novel thin wood strand composite of P. ponderosa, 3.2 mm thick, is introduced as a veneer substitute. Optimization was performed for the processing parameters phenol formaldehyde resin content, platen temperature, and the aspect ratio strand length to thickness (L/t). Mean modulus of elasticity and modulus of rupture values of 10.2 GPa and 79.1 MPa, respectively, were obtained with the optimized formulation (5.5% resin, platen temperature 152°C, and aspect ratio of 430). These values were approximately 2–2.5 times higher than the parent small-diameter ponderosa pine lumber. The results indicate that fast-growing low-density species – such as hybrid poplars, or small-diameter timber with predominantly juvenile wood – could potentially be used to manufacture strand veneers of consistent quality with significantly higher strength and stiffness than parent material.

Experimental analysis of multiple staple joints in selected wood and wood-based materials

Effects of the number and spacing between staples on withdrawal and lateral resistance of stapled joints were investigated for selected wood and wood-based materials. Galvanized staples with legs that were 1.59 mm in diameter (16-gage wire) and 38 mm (1.5-in.) in length, and had chisel-end points, were used to construct the joints. Spacings between staples of 3.18 mm (1/8-in.) and 6.35 mm(1/4-in.) were tested. One, two, four, or eight staples were used to fasten the joint members that were of the following materials: Eastern cottonwood (Populus deltoides), red oak (Quercus falcata), yellow poplar (Liriodendron tulipifera), sweetgum (Liquidambar styraciflua), medium density fiberboard (MDF), and oriented strandboard (OSB). Direct withdrawal and lateral resistances of the joints were evaluated. Results indicated that, on the average, joints with higher density members provided the most resistance to withdrawal and lateral loads. Number of staples positively affected the joint resistance for all materials for both spacings, however, the relationship was not linear for most materials. General linear regression models, using material type and spacing as indicator variables, were developed to predict the withdrawal and lateral resistances.

Manufacture of laminated strand veneer (LSV) composite. Part 2: Elastic and strength properties of laminate of thin strand veneers

Abstract Laminated strand veneer (LSV) is a new engineered wood-strand composite consisting of laminated thin (3 mm) strand veneers (see Part 1 of this study). Advantages include utilization of low-density small-diameter timber, good mechanical properties for structural applications, and the ability to engineer the lay-up of laminates for specific end uses. In the present paper, the feasibility of the concept of engineering laminated composites made of thin strand veneers is scrutinized. Properties of individual strand plies and laminated products manufactured with strand plies were determined and compared with traditional wood composite panel properties and predictions based on the classical lamination theory (CLT). Elastic and strength properties of LSV composites compare favorably with plywood and laminated veneer lumber composites made of veneer, and exceeded those of oriented strand board and particleboard. It was shown that the CLT model was useful in engineering composite lay-ups to give an approximation of LSV composites properties. Strength and stiffness of LSV are 100–150% higher than that of the small-diameter parent wood from which it was formed.