Load tests of adhesive assembly bonding under defined climatic conditions with beech and meranti

It could be proved that the four types of adhesives, all of them classified by the resp. manufacturer into group of stress D 4 according to EN 204, differ distinctly from each other in behaviour when exposed to load tests as stipulated in BS 3544 resp. DIN 53254, paragraph 8.2. Seven days of storage under normal climatic conditions (20/65) were not sufficient in most cases to reveal these differences. The same holds true for 10 days of storage as stipulated in the European draft for standardisation of the static load test. Longer periods of load and/or storage under different climatic conditions were necessary for the findings. In general, the KPVAC adhesive with Iso-linking and the KPUR adhesive showed better behaviour to static load than did the KPVAC adhesive with either aluminium or chromium hardener. Wet climatic conditions (20/65) lead to faster and more fracture, whereas dry climatic conditions (20/30) apparently increase elasticity of adhesion, thus improving strength against static load. Under alternating climatic conditions (dry- wet), fractures always occurred in the wet period. Quality of adhesion is considerably influenced by the species of wood employed. This could clearly be proved in the load tests conducted. Type of adhesive, species of wood and climate, therefore, are important parameters, which by all means have to be taken into account in order to get reliable data concerning static load capacity of adhesive assembly bonding.