The influence of fracture energy on wooden structural members due to contact explosion

Abstract

In military operations, sappers must often breach wooden structures. The formulas for determining the destructive explosive loads available in instructions and manuals used by sappers are simplified because they consider only a few variables, such as structure member diameter, whether the wood is dry or damp, or the wood species of the structure. In this study, the destructive explosive loads needed to breach pine, birch and oak members were computed via the finite element method. Static compression tests in three directions were conducted to define the orthotropic constitutive models of those wood species, and the results were used as an input to the numerical models. The damage model for wood considered different levels of energy criteria. The finite element analyses of contact explosion of TNT charges against cylindrical log beams were conducted for selected wood species, and destructive explosive loads were computed for different log diameters. Assuming different energy criteria, the results showed that the traditional approach in military instructions and manuals is higher than the values obtained from the numerical approach, i.e., standard manuals suggest using more explosive than may be needed.