Analysis of glue line and correlations between density and anatomical characteristics of Eucalyptus grandis × Eucalyptus urophylla glulam

Rafael G E De Oliveira,Pedro G De A Segundinho,Izabella L S Chaves,Fabricio G Gonçalves,Juarez B Paes,José T Da S Oliveira,Alice S Brito

doi:10.4067/s0718-221x2020005000408

Abstract

This study aimed to analyze the glue line thickness effect and its relation with the density and anatomical characteristics of eucalyptus wood. Thus, the thickness of main and secondary glue lines was measured as well as their interaction with the apparent density of elements glued with resorcinol-formaldehyde (RF) and castor oil polyurethane (CP) adhesives. Anatomical wood characterization of Eucalyptus grandis × Eucalyptus urophylla was performed by correlating glue line thickness. According to normative instruction, specimens were produced for delamination tests. The experiment was conducted in a completely random 2 × 2 design factorial scheme (two classes of wood apparent density and two adhesives). Pearson correlation (t < 0,01) was performed among variables. It was found that there was adhesive penetration into vessels and rays of wood. Glue line thickness was higher in woods with density higher than to 580 kg/m3 glued with RF adhesive. There was a low correlation between wood density and vessel diameter to main and secondary glue lines (t < 0,01)

Highlights

Glued laminated timber (Glulam) is a structural product obtained by gluing pieces of timber with fibers parallel to each other (Bodig and Jayne 1993)
The market still needs to know more information about the mechanical resistance of this product; to understand how Glulam will work it is important to evaluate the behavior of some variables, such as apparent density and timber glued with adhesive
Physical and anatomical characteristics of wood. These characteristics have an influence on adhesive penetration (Marra 1992), pressure need, pressing time and adhesive cure, making its determination an indispensable factor to produce Glulam elements (Segundinho et al 2015)

Summary

Introduction

Glued laminated timber (Glulam) is a structural product obtained by gluing pieces of timber with fibers parallel to each other (Bodig and Jayne 1993). The market still needs to know more information about the mechanical resistance of this product; to understand how Glulam will work it is important to evaluate the behavior of some variables, such as apparent density and timber glued with adhesive. Proportion of empty spaces combined with dimensions and arrangement of cellular elements have influence on adhesive mobility and penetration into timber structure as in the resistance of glue line to delamination (Albuquerque and Latorraca 2000, Konnerth et al 2008, Lopes 2008, Singh et al 2008, Stoeckel et al 2013, Gonçalves et al 2019). When low density (higher frequency and diameters of vessel, with high and wide rays), it may allow excessive penetration of adhesive, if the adhesive does not present an ideal viscosity and formation of good glue line (Albuquerque et al 2005, Albino et al 2010)

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Conclusion