A study was conducted with the primary objective of gathering information for the development of a protocol for evaluating the surface quality of cross-laminated timber (CLT) products. The secondary objectives were to examine the effect of moisture content (MC) reduction on the development of surface checks and gaps, and find ways of minimizing the checking problems in CLT panels. The wood materials used for the CLT samples were rough-sawn Select grade Hem-Fir boards 25 x 152 mm (1 x 6 inches). Polyurethane was the adhesive used. The development of checks and gaps were evaluated after drying at two temperature levels at ambient relative humidity (RH).
The checks and gaps, as a result of drying to 6% to 10% MC from an initial MC of 13%, occurred randomly depending upon the characteristics of the wood and the manner in which the outer laminas were laid up in the panel. Suggestions are made for minimizing checking and gap problems in CLT panels. The checks and gaps close when the panels are exposed to higher humidity.
Guidelines were proposed for the development of a protocol for classifying CLT panels into appearance grades in terms of the severity of checks and gaps. The grades can be based on the estimated dimensions of the checks and gaps, their frequency, and the number of laminas in which they appear.
A joint research project was carried out under the fund of Value to Wood Program. The project is to further develop the range of possible applications for hollow core panels (HCPs), to construct and test prototypes for more demanding applications and to create optimization tools through the development of finite element models (FEM) for these geometrically complex assemblies for minimized materials content and optimized panel structure. The experimental works that mostly involved with development of alternative low density core materials that can be used for light weight sandwich panels were conducted in FPInnovations Quebec lab while the research team from University of Toronto worked for FEM modeling and the research team from University of British Columbia investigated a range of different applications of the light weight sandwich panels.
This report documents the research project done at FPInnovations with detail description of research methodology, results, conclusions and recommendation. It consists six sub-reports:
1. Development of Two-Stage Thermo-Reforming Technology for the Manufacturing of Cup-Shape Fibreboard. Part I. Investigation of Effects of Different Resin Systems and Secondary Hot Pressing on Panel Properties.
2. Development of Two-Stage Thermo-Reforming Technology for the Manufacturing of Cup-Shape Fibreboard. Part II. Manufacture of the Cup-Shape Fibreboard Panels.
3. Low Density Particleboard Made with Speciality Isocyanate and Polyurethane Based Resins.
4. Manufacture of Low Density Particleboard Using Lab Made Polyurethane Based Resin.
5. Effect of Wood Particle Geometry on the Density and Strength of Low Density Particleboard.
6. Development of Low Density Particleboard Using Hemp Shives and MDI Resin.