Fracture toughness of structural adhesives for the automotive industry

Alfano, Marco; Morano, Chiara; Moroni, F.; Musiari, F.; Spennacchio, Giuseppe Danilo; Lonardo, Donato Di

doi:10.1016/j.prostr.2017.12.055

Cited by 10 publications

(9 citation statements)

References 2 publications

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“…The toughness of the mono-component adhesive was found to be in the range (1.45 ± 0.26) kJ/m 2 . It is emphasized that previous related work by the authors 28 indicated that the quoted toughness does not display substantial variations with the bondline thickness. After conditioning, the T-joints still failed in steady-state fashion and the toughness, which was once again estimated using the ESIS protocol, was reduced of about 29%.…”

Section: Resultsmentioning

confidence: 65%

“…The results pertaining to the bi-component adhesive displayed a similar pattern, even if the fracture toughness of the pristine joints was higher than that of the mono-component adhesive and was equal to (1.74 ± 0.52) kJ/m 2 ; once again, the results did not show significant dependency on the bondline thickness. 28 After aging, the toughness was lowered by 11%. An overall account on the obtained results is reported in Table 3.…”

Section: Resultsmentioning

confidence: 99%

“…The arrows point to the glass beads that are embedded in the adhesive, as also highlighted in the authors' previous study. 28 (b) Mono-component epoxy adhesive.…”

Section: Resultsmentioning

confidence: 99%

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Experimental analysis of steel joints bonded with automotive grade hot setting structural adhesives

Morano

Musiari

Moroni

et al. 2018

Proceedings of the IMechE

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Recent trends in car body manufacturing indicate that the use of a consistent mix of lightweight materials in conjunction with adhesive bonding, not only allows substantial weight reduction, but can also drive down costs and potentially enables more intelligent designs. Yet, presently, it is highly desirable that the introduction of structural adhesives is made with minimum impact on the automotive body framing systems. Adhesives commonly deployed in car body production (i.e. body-in-white) are applied without any prior surface preparation and final curing is carried out during the baking process that follows the electrophoretic coating. Several structural adhesives have been tailored to the conditions dictated by the automotive production process. The aim of this work is to assess the mechanical properties of adhesive joints bonded with automotive grade hot setting epoxy adhesives employed for the assembly of frame and panels. Single-lap and T-joints were fabricated and adhesive hardening was carried out following the typical curing cycle employed in the process chain of automobile production. The resulting mechanical properties were assessed before and after exposure to a standard accelerated thermal cycling under controlled humidity. The evaluation of the mechanical behavior was done through a combination of testing and analysis, which included the assessment of fracture surfaces using optical microscopy to resolve the locus of failure.

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Section: Resultsmentioning

confidence: 65%

Section: Resultsmentioning

confidence: 99%

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Experimental analysis of steel joints bonded with automotive grade hot setting structural adhesives

Morano

Musiari

Moroni

et al. 2018

Proceedings of the IMechE

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“…Simultaneously, automobile and adhesive manufacturers have carefully considered and studied the reliability of adhesives in automobiles, where human safety must be guaranteed. The essential basic requirements for automotive structural adhesives are as follows: an elongation performance, in addition to the adhesive strength (i.e., the toughness) [ 19 , 20 , 21 ]; an impact resistance [ 22 , 23 , 24 ]; and a stable performance in the specified operating temperature range [ 25 , 26 , 27 ]. The toughness is required because a vehicle in the driving state experiences various external forces.…”

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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“…However, due to their high density of three-dimensional molecular structure, hardly can they resist toward growing of crack. This serious drawback limits their applications in many critical elds where a notable fracture strength or low-temperature toughness is required, such as aerospace and automotive industries [2] [3]. To deplete the severity of this issue, a plethora of different ingredients such as liquid rubbers, core-shell particles (CSIMPs), and rigid organic and inorganic ingredients were used as impact modi ers particles (IMPs) of epoxy resin [4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Synergistic effects of multiwalled carbon nanotubes and core-shell particles on the toughness and physico-mechanical properties of epoxy resin: a systematic study

Gharieh

Dorraji

2021

Preprint

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Here, core-shell impact modifier particles (CSIMPs) and multiwalled carbon nanotubes (MWCNs) were used as reinforcing agents for improving toughness and tensile properties of epoxy resin. For this purpose, emulsion polymerization technique was exploited to fabricate poly(butyl acrylate-allyl methacrylate) core- poly(methyl methacrylate-glycidyl methacrylate) shell impact modifier particles with average particle size of 407 nm. It was revealed that using a combination of the prepared CSIMPs and MWCNTs could significantly enhance toughness and tensile properties of epoxy resin. Also, it was observed that the dominant factors in enhancing the fracture toughness of the ternary composites are crack deflection/arresting as well as enlarged plastic deformation around the growing crack tip induced by the combination of rigid and soft particles. The Response Surface Methodology (RSM) with central composite design (CCD) was utilized to study the effects of the amounts of core-shell particles and multiwalled carbon nanotubes on the toughness and tensile properties of epoxy resin. The proposed quadratic models were in accordance with the experimental results with correlation coefficient more than 98%. The optimum condition for maximum toughness, elastic modulus, and tensile strength were 3 % wt. MWCNT and 1.03 % wt. CSIMPs. The sample fabricated in optimal condition indicated toughness, elastic modulus, and tensile strength equal to 2.2 MPa. m1/2, 3014.5 MPa and 40.6 MPa, respectively.

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Fracture toughness of structural adhesives for the automotive industry

Cited by 10 publications

References 2 publications

Experimental analysis of steel joints bonded with automotive grade hot setting structural adhesives

Experimental analysis of steel joints bonded with automotive grade hot setting structural adhesives

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

Synergistic effects of multiwalled carbon nanotubes and core-shell particles on the toughness and physico-mechanical properties of epoxy resin: a systematic study

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