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Gewählte Doctoral Thesis:

Doctoral Thesis, BOKU-Universität für Bodenkultur, pp 156. UB BOKU obvsg

Data Source: ZID Abstracts
The major part of the thesis deals with the mechanical characterisation of end grain joints. In general, wood experts and craftsman expect much lower mechanical stability for such joints than for flat grain joints. Mainly three-parted test specimens were prepared. By variation of the grain angle of the middle part from 0° to 90° the whole spectrum starting from flat grain joints (0°) to flat grain to end grain or end grain to end grain joints, respectively, (90°) was studied. By application of modern adhesives higher bond strength of end grain joints was observed than expected. Depending on the type of strain applied to the specimens, influence of the grain angle on the bond strength was more or less pronounced. Various models were developed for the description of the different bonding mechanisms. Further,the influence of the density on the bond strength of an end grain to end grain joint was studied. A significant effect of density on the mechanical stability of the joint strength was found. By the use of a chemical primer, the surface of end grain wood could be altered such that the bond strength of an end grain to end grain joint was significantly enhanced. Similarly, thermal treatment led to a modification of the wood surface so that thermoplastic foils could be applied as adhesives. Bonding of honeycombs and web sandwich constructions include the formation of adhesive fillets at the transition from the vertically oriented webs and paper sheets to the horizontally oriented surface layers. Based on t-shaped specimens, the structural influence of adhesive fillets on the bond strength of end grain to flat grain joints was investigated. Significant effects on both, bond strength as well as reduction of notch stress was found.

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