Künstliche Alterung von Holzverklebungen und ihre Auswirkung auf die Querzugfestigkeit unter besonderer Berücksichtigung einer Längs-Hirnholzverklebung

Title
Künstliche Alterung von Holzverklebungen und ihre Auswirkung auf die Querzugfestigkeit unter besonderer Berücksichtigung einer Längs-Hirnholzverklebung

Author
Jürgen Follrich , Alfred Teischinger , Ulrich Müller

European Journal of Wood and Wood Products 2011 v.69 no.4 pp. 597-604

Abstract

The effect of ageing processes on internal bond strength of three-part specimens produced from Norway spruce wood (Picea abies Karst.) bonded with one-component polyurethane (PUR), two-component emulsion polymer isocyanate (EPI), melamine-urea-formaldehyde (MUF) or phenol-resorcinol-formaldehyde (PRF) adhesive was studied. By varying the grain angle of the middle part from 0° (parallel to grain of the surface layers) to 90° (perpendicular to grain of the surface layers) in incremental steps of 10° the effect of grain direction was investigated. The specimens were exposed to a three-step ageing cycle lasting for seven days (50°C/95% relative humidity (rH), −20°C/65–70% rH and 75°C/15% rH) which was repeated twelve and twenty-four times, respectively. In general, a decrease in internal bond strength of the exposed specimens was observed. For all tested adhesive systems, influence of ageing processes was more pronounced for flat-to-end grain joints compared to longitudinal joints. For samples bonded with PUR adhesive strength reduction was lower compared to the other adhesives used.

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