The bending performance of T&G joints subjected to concentrated loads

The stiffness, considered to be the slope of the linear region of the load-displacement chart has been calculated. Linear regression lines between failure load and stiffness were sought. Relatively good correlation (R²=0.88) was found for the unjointed samples, however, less good correlation (R²=0.63) was found for the glued jointed samples and even worse correlation (R²=0.53) was found for the unglued jointed ones. Generally, the stiffness can be considered as a useful indicator for the failure load and failure mode of the particleboard samples. For increased stiffness values the boards tend to fail at higher loads and in a more brittle mode, providing a sudden vertical drop in the load/displacement curves. At values over 456 N/mm `catastrophic' failure modes (instant total failures) were observed (span size of 450 mm and thickness of the boards of 18 mm). However, at values less than 420 N/mm the failure mode was more ductile, described by `smooth' post failure curves. By gluing the joints the stiffness of the structure increases significantly. The failure load also increases but not by an amount that is statistically significant. The failure mode of glued jointed structures seems to be more ductile when compared to unglued ones. This means that after the maximum failure load has been achieved, the boards continue to sustain the load for a longer period of time up to ultimate failure occurs.

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=0,88), schwache für verleimte Proben (R²=0,63) und noch schwächere für unverleimte Verbindungen (R²=0,53). Allgemein erwies sich die Steifigkeit der Spanplatten als guter Indikator für die zu erwartende Bruchlast und die Art des Bruchs. Bei erhöhter Steifigkeit erfolgte der Bruch bei höherer Belastung, war zunehmend spröder und zeigte als ein plötzlicher senkrechter Abfall in der Verformungskurve. Bei Werten oberhalb 456 N/mm erfolgte ein unmittelbares totales Versagen (Katastrophenfall). Bei Werten unterhalb 420 N/mm war der Bruchverlauf zäher mit “sanfterem” Kurvenverlauf nach dem Bruch.