Open Access

ARTICLE

The Characteristics of Glued Tensile Shear Strength Constituted of Wood Cut by CO₂ Laser

by Fatemeh Rezaei^1,2,*, Milan Gaff^1,3,4,*, Róbert Nemeth⁵, Jerzy Smardzewski⁶, Peter Niemz⁷, Haitao Li^8,9, Anil Kumar Sethy^1,10, Luigi Todaro¹¹, Gourav Kamboj¹, Sumanta Das¹, Roberto Corleto¹, Gianluca Ditommaso¹, Miklós Bak⁵

1 Department of Wood Processing, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Prague, 16521, Czech Republic
2 Department of Wood Science and Engineering, Oregon State University, Corvallis, OR, USA
3 Department of Furniture, Design and Habitat Brno, Mendel University in Brno, Brno, 61300, Czech Republic
4 Experimental Centre, Faculty of Civil Engineering, Czech Technical University in Prague, Prague, 16629, Czech Republic
5 Institute of Wood Technology and Technical Sciences, University of Sopron, Sopron, 9400, Hungary
6 Department of Furniture Design, Faculty of Forestry and Wood Technology, Poznan University of Life Sciences, Poznan, 60637, Poland
7 ETH Zurich, Institute for Building Materials, Lulea University of Technology, Zurich, CH, 8093, Switzerland
8 School of Civil Engineering, Nanjing Forestry University, Nanjing, China
9 Joint International Research Laboratory of Bio-Composite Building Materials and Structures, Nanjing Forestry University, Nanjing, China
10 Wood Properties and Processing, Institute of Wood Science and Technology, Bangalore, 560003, India
11 School of Agricultural Forestry, Food, and Environmental Science, University of Basilicata, Potenza, 85100, Italy

* Corresponding Authors: Fatemeh Rezaei. Email: ; Milan Gaff. Email:

Journal of Renewable Materials 2023, 11(8), 3277-3296. https://doi.org/10.32604/jrm.2023.028352

Received 14 December 2022; Accepted 01 March 2023; Issue published 26 June 2023

Abstract

The performance of engineered wood products is highly associated with proper bonding and an efficient cutting method. This paper investigates the influence of CO₂ laser cutting on the wetting properties, the modified chemical component of the laser-cut surface, and the strength and adhesive penetration near the bondline. Beechwood is cut by the laser with varying processing parameters, cutting speeds, gas pressures, and focal point positions. The laser-cut samples were divided into two groups, sanded and non-sanded samples. Polyvinyl acetate adhesive (PVAc) was used to bond the groups of laser-cut samples. After assembly with cold pressing, the tensile shear test was carried out. Numerical modelling was carried out to determine the partial elongation and shear strain of the glue line. Based on this, the shear modulus and linear elasticity of the glue line were estimated. Scanning electron microscopy was used to assess the adhesive penetration into the porosity structure of the laser-cut samples, and the depth of the heat-affected zone. The laser-cut surface was analysed by Fourier transform infrared spectroscopy. The wetting properties of the laser-cut surface were investigated by using a contact angle goniometer. The numerical model of the strain-stress curve confirmed the experimental model. The highest modulus of the linear elasticity of the glue in the numerical calculation belongs to the joint containing laser-cut samples at a gas pressure of 21 (bar). The penetration depth of PVAc adhesive into the porosity structure of the laser-cut samples was similar to that of sawn samples. The deepest heat-affected zone in the laser-cut samples was 150 µm. A PVAc drop disappeared immediately on the laser-cut surface without sanding, but gradually on the sanded surface. In contrast, the drop on the sawn surface remained with an angle of 32°–48°. The degradation of hemicellulose and lignin was proven by the lower intensity of the C=O and C-O Bonds, compared to the sawn surface.

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