Experimental and Numerical Determination of the Mechanical Properties of Spruce Wood

Gorazd Fajdiga,Denis Rajh,Branko Nečemer,Matjaž Šraml,Srečko Glodež

doi:10.3390/f10121140

Abstract

The objective of this paper is the computational and experimental study of the fracture behavior of spruce wood under quasi-static loading conditions during a three-point bending test. The experimental tests were performed on the electronic testing machine Zwick Z100 (Zwick-Roell GmbH & Co. KG, Ulm, Germany) with displacement control, according to the standard International Standard Organisation (ISO) 13061-4: 2014. The specimens were made of Norway spruce (Picea abies) wood, with dimensions of 25 mm × 25 mm in cross-section and 549 mm in length. Six tests were performed for each orientation (radial and tangential) of the wood fibres. Based on the experimental results, the computational model was created and validated by considering the mechanical responses in two different directions due to the orientation of the wood fibres. An orthotropic material model with damage evolution was selected as the computational model. The computational model was validated using the inverse procedure for the determination of the constitutive material parameters, including the damage parameters of three-point bending test specimens. A finite element method (FEM) in the framework of program package ABAQUS was used for the computational simulation, while the open code Optimax was used for the optimization procedure. Comparison between the experimental and computational force vs. the displacement response showed a very good correlation in the results for the spruce wood specimens under three-point bending tests, with Pearson′s correlation coefficient of r = 0.994 for the tangential and r = 0.988 for the radial orientation. Therefore, validation of the proposed computational model was confirmed, and can be used further in numerical simulations of the fatigue behavior of wood specimens.

Highlights

Wood is a material with mechanical properties that vary markedly, both within a tree and among trees
An orthotropic material model with damage evolution was selected as the computational model
The computational model was validated using the inverse procedure for the determination of the constitutive material parameters, including the damage parameters of three-point bending test specimens

Summary

Introduction

Wood is a material with mechanical properties that vary markedly, both within a tree and among trees. Products made from biological materials such as wood often have complex mechanical behavior. Such materials have been utilized for thousands of years, full knowledge of their mechanical behavior has yet to be achieved. They often vary in their properties from sample to sample, and exhibit a nonlinear mechanical behavior at higher loading. Wood is a typical heterogeneous material, it has recently been increasingly used as a construction material, which in practice is most often subjected to cyclic loading

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