Optimized test design for identification of the variation of elastic stiffness properties of loblolly pine (Pinus taeda) pith to bark

Abstract

This article presents the design optimization of an un-notched Iosipescu test specimen whose goal is the characterization of the material elastic stiffnesses of a Loblolly (Pinus taeda) or Lodgepole pine (Pinus contorta) sample in one single test. A series of finite element (FE) and grid simulations were conducted to determine displacement and strain fields for various ring angles, ring spaces, and proportions of latewood per ring. These displacement and strain fields were utilized to determine the constitutive parameters for the woody material using VFM. Using an error function based on a comparison of the input stiffnesses and those identified by grid simulation information it was possible to narrow the optimum ring angle at which test specimens should be tested. The results of this work suggest that the starting angles for the unnotched Iosipescu test specimens should be approximately 45º to produce the smallest identification error.