Microscopic investigation of defects in thermally compressed poplar wood panels

Dilek Dogu,Oner Unsal,Kamile Tirak Hizal,Davut Bakir,F Digdem Tuncer,Zeki Candan

doi:10.4067/s0718-221x2016005000031

Dilek Dogu, Oner Unsal + Show 4 more

Open Access

https://doi.org/10.4067/s0718-221x2016005000031

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Abstract

The combined effects of temperature and compression on the microstructure of solid-wood panels produced by Aspen (Populus tremula) wood were evaluated. Thermal compression was applied on aspen wood to increase the density for improving its physical and mechanical properties. The solid wood panels with dimensions of 100 mm by 500 mm by 25 mm were hot-pressed by using a laboratory hot press at a temperature of either 150 °C or 170 °C and pressure of either 1MPa or 2 MPa, respectively, for 45 min. Changes in the microstructure were detected by using a light microscope. The microscopic investigations revealed that the wood exhibited much defects in the process conditions of 170 oC / 2 MPa, and the distribution of defects were not uniform in the growth rings of the wood specimens in the two treatment groups. All defects in cell structure were quite distinct in the beginning and the last parts of the growth rings and the largest damages occurred in the fibers and vessels for the two process conditions. The results indicate that growth ring structure, vessel porosity, and cell wall thickness have a strong effect on wood behavior in various process conditions.

Highlights

In comparison to many other materials, wood is unique
This study was performed on wood samples, which exposed to two different thermal compression process, were taken from the materials examined by Candan et al (2013b)
Light Microscopy (LM) was employed to reveal deformations in the anatomical structure of the panels subjected to varying thermal compression conditions

Summary

Introduction

In comparison to many other materials, wood is unique. It has been used throughout the history mostly because of its low cost, renewability, strength properties, and low processing energy requirements. It is thought that timber production may not be able to meet the needs of forest products industry in the future. To overcome this phenomenon, the plantation forests and the fast growing tree species have received great attention during the last years (Hill 2006). Wood formation with low density restricts the industrial usage of timber from fast-grown tree species. Most of the mechanical and physical properties of wood are clearly correlated with its density (Blomberg 2006)

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