Static and dynamic tensile shear test of glued lap wooden joint with four different types of adhesives

Abstract

Investigations of quasi-static and fatigue failure in glued wooden joints subjected to tensile shear loading are presented. Lap joints of beech wood (Fagus sylvatica L.) connected with four different types of adhesives, i.e. polyurethane (PUR), melamine urea formaldehyde (MUF), bone glue and fish glue, were experimentally tested until the specimens failed. The average shear strengths obtained from the quasi-static test ranged from 12.2 to 13.4 MPa. These results do not indicate any influence of the different adhesive types. The influence of the adhesives is only visible from the results of the fatigue tests, which were carried out under different stress excitation levels between 45% and 75% of the shear strength. Specimens bound with ductile adhesive (PUR) showed a slightly higher number of cycles to failure (Nf) at low-stress levels and lower Nf at high-stress levels in comparison to more brittle adhesives (MUF, fish glue). In general, the performances of animal glues and MUF were similar in both quasi-static and fatigue loading under dry conditions.

Reaction kinetics investigation in relation to the influence of humidity on fatigue behavior of wood lap joints

“…It seems, therefore, that the use of a probabilistic model to determine the endurance limit gives satisfactory results compared to literature values. The endurance limit of the data presented by Bachtiar et al (2017) for MUF and the 1C-PUR adhesive tested at 23°C, 50% RH was estimated to be 19% and 26% of the ultimate strength, respectively, which is in the same range as the data presented here.…”

“…For a RH of 35% and 50%, both 1C-PUR adhesives can run a higher number of cycles for the same relative strength than the PRF adhesive. Even though the differences were small between the HB 110 and PRF adhesives at a RH = 35%, the higher endurance limit of the HB 110 seems to confirm the hypothesis of Bachtiar et al (2017) that ductile adhesives such as both the 1C-PUR perform better under low cyclic fatigue. This hypothesis should, however, be confirmed with additional samples especially at a RH of 35%.…”

“…Even though the influence of the adhesive properties on the quasi-static (QS) properties of wood-glued joints is a field that has already been well studied (Stoeckel et al 2013), few recent papers have specifically investigated the influence of different types of adhesives on the fatigue performance of bonded wood. Recently, Bachtiar et al 2017 showed that adhesives with different elastic moduli have led to different fatigue performances, which were not obvious under QS loading conditions. The brittle adhesive systems [melamine-ureaformaldehyde (MUF), fish and bone glue] seem to perform well under high-intensity, low-cycle fatigue (LCF), while the more ductile adhesive one-component polyurethane (1C-PUR) system performs better under low-intensity, highcycle fatigue (HCF).…”

“…It is possible that the ductile 1C-PUR dissipate a higher amount of strain energy into heat, which is consequently not available for damage accumulation (Künniger et al 2019). Even though different adhesion phenomena are observed depending on the chemicals nature of the adhesive systems, it remains generally valid that brittle-tested adhesives possess a denser interconnected polymer network, responsible for the high elastic modulus and providing also basically more connecting points to the wood, resulting in better adhesion and a higher wood fracture percentage (WFP) (Bachtiar et al 2017). It remains, however, unclear how the wood moisture content, type of loading and the type of adhesive influence the shape of the stress-cycle number curve (S-N curve) especially for HCF.…”

The Strength of the Adhesive Joints of the Medium-Density Fireboards and Particle Boards with the PVC Film

“…A minimum contraction occurs at the bond during the bonding process. As a result, the adhesive is distributed evenly in the adhesive-bonded joint and does not cause any stresses, which enables to obtain a specified dynamic strength [7,8].…”