Prediction for Bending Strength of Cedar Wooden-shingle Boards based on Colorimetric Values

: Cedar wooden-shingle boards used as the Japanese traditional roofing material are handmade by craftsmen, and there is a need for technology that stabilizes its product performance. Therefore, the purpose of this study is to establish a method for quantitatively selecting cedar wooden-shingle boards by non-destructive methods based on color of the board, as done by craftsmen. Hence, in this report, a relationship was analyzed to evaluate the boards’ strength from colorimetric values by using a “transverse direction 3-point bending test”. As a result of multiple regression analysis, CIE L*, a*, and b* were adopted as coefficients, and confirmed that the maximum bending stress of the test piece can be predicted with a high correlation based only on the color. Furthermore, data from different types of color measurement instruments were compared and similar findings were observed.