Shear strength parallel of the wood fiber stress by punching – proposed test

Abstract

This research aims to propose a method for testing the shear strength of wood parallel to fiber and compare with other proposed methods. The method proposed by NBR 7190/1997 Brazilian Standard, that is similar to ASTM D 143-09/2010, the uses a rectangular prismatic specimen with an indentation to prevent its rotation, which it is caused by the asymmetry in the application of force that promotes the shear. In order to eliminate this asymmetry, the proposed procedure applies shear stress by punching a simple prismatic test specimen without cuts, with the distribution of shear section symmetrically in relation to a point. There upon, it's developed a male and female tool adapted to a universal test press for force application. Once the consistency of the method is verified, it's been carried out a series of tests with three different wood species (Pinus sp, Erisma uncinatum and Mezilaurus itauba), distinguished by their mechanical strength, inspecting the method by Santos Neto (1999) under the NBR 7190/1997 Brazilian Standard, and comparing it with the proposed method - punching. The outcomes showed that the testing with NBR 7190/1997 Brazilian Standard methods and the proposed method displayed similar and close results between them.