Methodology and device to obtain torsional shear strength of glued joints

Abstract

This paper presents a methodology to obtain the shear strength of glued joints, at the torsion moment. In the current standards this strength is measured by compression tests. The device designed for this purpose are also presented. The motivation for this test is related to the possibility of execution of glued wooden structures with joints under bending moment, shear force and normal force simultaneously. It was admitted the hypothesis that the joint strength can be different depending on the test type. The methodology is relatively simple and in order to obtain the results classic equations from Mechanics of Materials were used. The strength results of 198 test specimens, tested by standard methodology, were compared, with an equal number of specimens made and tested with the proposed methodology, resulting in 396 tests. 208 specimens were glued with resorcinol-formaldehyde and 188 with castor oil-based adhesive. The wood used was Eucalyptus sp. The specimens were made according to seven series involving gluing with the following angles between the fibers: 0°, 15°, 30°, 45°, 60°, 75° and 90°. Regardless of the adhesive type, there was a significant difference for the strengths presented by the two methods. From the seven angles studied, it was noticed a difference in six of them, except for the 30° series. The compression shear strength was severely affected by the gluing angle, with increasing losses towards higher angles. On the contrary, the strength offered by the joints tested by torsion did not seem affected by the gluing angle.Keywords: wood; adhesive; characterization; procedure.

Avaliação da fórmula de Hankinson como estimadora da resistência de juntas coladas sob compressão e desempenho mecânico de juntas coladas sob torção

“…Em todos os experimentos os corpos de prova rompidos à compressão foram confeccionados e ensaiados adotando-se a metodologia proposta pela American Society for Testing and Material -ASTM D-905 (2013). No caso dos corpos rompidos à torção, adotou-se a metodologia proposta por Petrauski et al (2020).…”

“…Contudo, para os Trabalhos 2 e 3, isto já foi feito por Petrauski et al (2020). Os autores propuseram uma metodologia para ensaio de juntas coladas sob torção ou momento de torção.…”

“…Na Tabela 5 apresenta-se o resumo das evidências obtidas por Petrauski et al (2020). Observa-se que tanto para o adesivo à base de óleo de mamona quanto para o adesivo Resorcinol Formaldeído, há diferença na resistência apresentada em seis das sete séries estudadas.…”

“…Consideradas as condições de desenvolvimento das pesquisas aqui exploradas, sugere-se a condução de pesquisas complementares, na perspectiva de usar outras espécies de madeira, tais como coníferas de reflorestamento, na condução da caracterização da resistência de juntas coladas em ângulos, incluindo o ensaio normatizado e o proposto por Petrauski et al (2020). Sugere-se, também, utilizar adesivos poliuretanos comerciais, para além do óleo de mamona, na caracterização de juntas coladas em ângulos.…”

Shear Strength of Pine Wood Bonded Joints With Different Angles Obtained Using Compression and Torsional Testing Methods

“…Concerning the origin of the shear stresses, structural connections may be subject to both shear stresses due to normal loads, such as in compression, and shear stresses due to torsional loads. The shear stresses with both origins can act at the same time on the connection, both being relevant for the design of structural connections (Petrauski et al, 2020;Stringari et al, 2020;Possa et al, 2022). In this regard is relevant to point that these diff erent loads lead to diff erent orientations of the stress in relation to the wood fi bers in the connection.…”