Soy flour was partly substituted for urea-formaldehyde (UF) resin with different content to investigate its effect on formaldehyde emission in three-layer plywood panels. In each square meter of panels, 300 g of resin was used (wet weight basis of resin). Micron-sized wollastonite was added to the resin mixture at 5% and 10% consumption levels (wet weight basis of resin) to determine its potential effects as a reinforcing filler to mitigate the negative effects of addition of soy flour. Results showed a decreasing trend in formaldehyde emission as soy flour content increased to 20%. The highest shear-strength values were observed in panels with 10% and 15% soy flour content. The addition of wollastonite did not have a significant effect on formaldehyde emission, but it decreased the shear strength in soy-treated panels, although the values were still higher than those of control panels. Wollastonite significantly mitigated the negative effects of soy flour on the water absorption and thickness swelling of panels. It was concluded that 10% of soy flour and 5% of wollastonite provided the lowest formaldehyde emission and the most optimum physical and mechanical properties.

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A study was conducted to examine the effects of tenon geometry on the bending moment capacity of simple and haunched mortise and tenon joints under the action of both compressive and tensile loads. The effects of tenon width (25, 37.5, and 50 mm), tenon thickness (7.5, 10, and 15 mm), and tenon length (20, 25, and 30 mm) were examined. All of the joints were constructed of Turkish beech (Fagus orientalis Lipsky) and were assembled with a 40% solid-content polyvinyl acetate. Optimum results were obtained with joints constructed with 10-mm-thick tenons that were 37.5 mm wide by 30 mm long. Tenon length was found to have the greatest effect on joint capacity, whereas tenon width was found to have a much smaller effect. Joints constructed with 37.5-mm-wide haunched tenons had essentially the same moment capacity as joints constructed with 37.5-mm simple tenons. Optimum tenon width was 10 mm (1/3 of rail thickness); joints constructed with 10-mm-thick tenons had greater capacity than joints constructed with either 7.5-or 15-mm thick tenons.

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