Determination of Shearing Properties for Tubular Pinewood under Torsion

In this study, tubular pinewood (Pinus sylvestris L.) specimens are tested and shear strain measurements are performed by applying torsion in z direction in the consideration of light weight aircraft engineering. The objective of this paper is to contribute and generate the nonlinear material model in terms of shear modulus presented with power functions under the consideration of nonlinear behavior of wood under torque. Strain gauge measurements are performed for the maximum shear stresses which develop on the tubular specimen, along the radial r(rin, rout), circumferential Φ(Φin, Φout) and z directions, in a point-wise manner. The data is gathered and examined for the determination of the local variations of empirical shear modulus functions on transversely isotropic surfaces of the specimens. The coordinate dependent shear modulus functions of GzΦ(r), GzΦ(Φ), GzΦ(z) are derived for GzΦ(r, Φ, z)as the function of r, Φ and z, respectively, by analyzing the gathered data. It is proposed to represent the shear modulus functions, GzΦ(Φ) and GzΦ(z) with the parabolic polynomials, and, to represent the shear modulus function GzΦ(r) with a linear equation.

Microscopic Characterisation of Pinus sylvestris Cell Structures under Compression Loading

This study is mainly focused on the 3D mechanical cell deformations of 20 × 20 × 60 mm sized softwood specimens under 35 - 40 MPa compression loading at room temperature of 20?C. The moisture content of the specimens was 6% - 7%. The data of microscopic images were measured and compared in terms of the permanently degenerated individual cell structures each in micro-scale . 3D cell deformations of tissues were observed with a magnification of (×100) - (×1500) and in the range of 3.0 - 5.0 kV voltage under the SEM microscope. The specimens were examined under magnification and photographed before and after the compression loading applied parallel to the grain angles to the wood samples. Specimens were painted with gold liquid (12 × 12 × 12 mm sized specimens) in obtaining the SEM images. Under the SEM, these specimens were photographed and lengths between the cell walls ranged between 15 to 40 micrometers. In this study, relative deformations of pinewood cells were determined statistically considering the percentage permanent deformation under the compression loading. It was performed by using knowledge of structural mechanics, considering the measurement of permanent deformation in honeycomb-pinewood structure material.