Block Shear, Cross-Lap Tension, and Glueline Cleavage Methods of Testing Glued Joints

The glueline cleavage test appeared to be the most suitable for distinguishing between glues on the basis of strength values, since percentages of wood failure in this test were much lower than in the tension and cleavage tests on both tawa and radiata pine. Both the cross-lap tension test and the block shear test consistently resulted in high percentages of wood failure in both species with resorcinol and urea-resin glues. Only polyvinyl emulsion glue were gave low wood failure in these two tests. Distinction between glues from the results of the shear and tension tests must then be based mainly on estimates of wood failure, rather than on actual joint strengths. Independent estimations of wood failure percentages by the two authors on the groups of broken specimens from all three tests showed close agreement. There was no consistent pattern of difference in the shcar tcsts on tangential and radial grain specimens with any of the glues or species, since percentages of wood failure were generally high, and strength values reflected the differences in the strengths of wood in the two orientations.

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