Experimental investigation of the effects of adhesive thickness on the fracture behavior of structural acrylic adhesive joints under various loading rates

Sekiguchi, Yu; Sato, Chiaki

doi:10.1016/j.ijadhadh.2020.102782

Cited by 23 publications

(9 citation statements)

References 32 publications

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“…To achieve better performances avoiding too large mismatch in terms of thermo-elastic properties, structural adhesives and adherents have, in some cases, an equivalent stiffness. Some examples can be cited: acrylic adhesives, whose Young's modulus (E) is around 2-3 GPa [1], are used in manufacture of plywood (E = 5 − 8 GPa); phenolic and epoxy adhesives with E = 3−5 GPa [2] are used to bond structures of GFRP (polyester-glass composites) with E = 15 − 28 GPa; orthodontic adhesives with E = 18 − 22 GPa [3] are usually used for cementation of brackets on enamel (E 65 GPa).…”

Section: Introductionmentioning

confidence: 99%

A micromechanical model of a hard interface with micro-cracking damage

Raffa

Lebon

Rizzo

2022

International Journal of Mechanical Sciences

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Bonding techniques are increasingly used in many industrial fields. Modelling the under-load damaging behavior of hard structural adhesives is still an open challenge. This work proposes a new hard interface analytical model with evolutive micro-cracking damage. The model is obtained within a rigorous theoretical framework combining asymptotic theory and micromechanical homogenization. Main new features are: (i) the adoption of two dual homogenization approaches; (ii) the formulation of a thermodynamically-based damage evolution law for hard interfaces. The interface model is able to describe both ductile and brittle damage behavior of hard structural adhesives. Provided examples on the structural behavior, under several loads, suggest the suitability of the proposed interface model as a modelling strategy for hard structural adhesives with micro-cracking damage.

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Section: Introductionmentioning

confidence: 99%

A micromechanical model of a hard interface with micro-cracking damage

Raffa

Lebon

Rizzo

2022

International Journal of Mechanical Sciences

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“…In many cases of toughened epoxy adhesives, the fracture energy stopped increasing at a certain thickness, generally less than 1 mm [ 44 , 55 ]. However, with some types of structural acrylic and structural polyurethane adhesives, the fracture energy continued to increase even after the thickness exceeded 1 mm [ 49 , 56 ]. The experimental results revealed that this tendency was maintained even during the fatigue tests.…”

Section: Resultsmentioning

confidence: 99%

“…The adhesive bond-line thickness,

, was varied holding other parameters in a fixed state, as shown in Table 1 , and the effect of thickness on fatigue characteristics was investigated. According to a previous study [ 49 ], a linear increase in fracture toughness with respect to adhesive thickness was predicted for the SGA adhesive used when

mm. Therefore, the adhesive thickness was gradually changed within a range of

mm.…”

Section: Methodsmentioning

confidence: 99%

“…Under the quasi-static loading, not only the adhesive thickness but also the surface micro-patterns change the fracture process zone area that leads to an increase in the fracture energy [ 48 ]. In the case of structural acrylic adhesives, it has been reported that the fracture toughness becomes larger with larger bond-line thickness under a quasi-static condition and it approached the intrinsic work of the fracture

with the decrease in the plastic zone size under impact loading [ 49 ]. Further understanding of fracture behavior through experiments under cyclic loading is crucial for increasing the reliability of the joints bonded with structural acrylic adhesives.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Bond-Line Thickness on Fatigue Crack Growth of Structural Acrylic Adhesive Joints

Sekiguchi

Sato

2021

Materials

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With an increasing demand for adhesives, the durability of joints has become highly important. The fatigue resistance of adhesives has been investigated mainly for epoxies, but in recent years many other resins have been adopted for structural adhesives. Therefore, understanding the fatigue characteristics of these resins is also important. In this study, the cyclic fatigue behavior of a two-part acrylic-based adhesive used for structural bonding was investigated using a fracture-mechanics approach. Fatigue tests for mode I loading were conducted under displacement control using double cantilever beam specimens with varying bond-line thicknesses. When the fatigue crack growth rate per cycle, da/dN, reached 10−5 mm/cycle, the fatigue toughness reduced to 1/10 of the critical fracture energy. In addition, significant changes in the characteristics of fatigue crack growth were observed varying the bond-line thickness and loading conditions. However, the predominance of the adhesive thickness on the fatigue crack growth resistance was confirmed regardless of the initial loading conditions. The thicker the adhesive bond line, the greater the fatigue toughness.

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“…There are structural adhesives that are based on epoxy, urethane, and acrylic materials [ 19 , 26 , 27 , 28 , 29 ]. Among them, epoxy-based structural adhesives are commonly adopted because of their excellent mechanical strength, chemical resistance, and environmental resistance.…”

Section: Introductionmentioning

confidence: 99%

Mechanical Characterization of Core-Shell Rubber/Epoxy Polymers for Automotive Structural Adhesives as a Function of Operating Temperature

2021

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Automotive structural adhesives must show a steady toughness performance in the temperature range of −40 °C to 80 °C, considering their actual usage environments. Core-shell rubber (CSR) nanoparticles are known to enhance the toughness of epoxy systems. In this study, a CSR, pre-dispersed, diglycidyl epoxy of bisphenol A (DGEBA) mixture at 35 wt % (KDAD-7101, Kukdo Chemical, Seoul, Korea) was used as a toughener for an automotive structural epoxy adhesive system. A simple, single-component, epoxy system of DGEBA/dicyandiamide with a latent accelerator was adopted, where the CSR content of the system was controlled from 0 to 50 phr by the CSR mixture. To determine the curing conditions, we studied the curing behavior of the system by differential scanning calorimetry (DSC). Modulus variations of the cured bulk epoxies were studied using a dynamic mechanical analyzer (DMA) in the dual cantilever mode. The flexural modulus of the cured epoxies at various temperatures (−40, −10, 20, 50, and 80 °C) showed the same tendency as the DMA results, and as the flexural strength, except at 0 phr. On the other hand, the strain at break exhibited the opposite tendency to the flexural modulus. To study the adhesion behavior, we performed single-lap joint (SLJ) and impact wedge-peel (IWP) tests. As the CSR content increased, the strength of the SLJ and dynamic resistance to the cleavage of the IWP improved. In particular, the SLJ showed excellent strength at low temperatures (32.74 MPa at 50 phr @ −40 °C (i.e., an 190% improvement compared to 17.2 MPa at 0 phr @ −40 °C)), and the IWP showed excellent energy absorption at high temperatures (21.73 J at 50 phr @ 80 °C (i.e., a 976% improvement compared to 2.07 J at 0 phr @ 80 °C)). The results were discussed in relation to the changes in the properties of the bulk epoxy depending on the temperature and CSR content. The morphology of the fracture surface was also provided, which offered useful information for composition studies using the CSR/epoxy system.

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Experimental investigation of the effects of adhesive thickness on the fracture behavior of structural acrylic adhesive joints under various loading rates

Cited by 23 publications

References 32 publications

A micromechanical model of a hard interface with micro-cracking damage

A micromechanical model of a hard interface with micro-cracking damage

Effect of Bond-Line Thickness on Fatigue Crack Growth of Structural Acrylic Adhesive Joints

Mechanical Characterization of Core-Shell Rubber/Epoxy Polymers for Automotive Structural Adhesives as a Function of Operating Temperature

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