Microtensile Testing of Wood – Overview of Practical Aspects of Methodology
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Microtensile testing is a specific and delicate variant of standard tensile testing and is performed on small samples. Often also referred to as “thin strip” method, the testing of thin veneers is described in this paper with particular aspects of its field and scope of application, along with comments on reliability and variability of results. Experimental guidelines of the precise technique are presented as well. The method consists of preparation of microtomed longitudinal wood sections, which may be treated or exposed to various conditions, agents or weathering, followed by tensile testing in a large number of replicas. Therefore, the reduction in size of samples shortens and/or facilitates the testing. Testing at zero span (the jaws of testing instrument being initially in contact) reflects to a greater extent the mechanical properties of the cellulose component, while the finite (usually 10 mm) span test yields more information about matrix properties i.e. lignin intercellular material and the degree of fibre bonding. This method has some shortcomings related to the fact that practical applicability is restricted to a small number of species, and that great skill is required to prepare the material, execute the testing and interpret the results. The method may be time consuming and technically demanding, depending on species and type of experiment.