Development of a fracture-mechanics based fatigue testing method for epoxy/electrical steel laminates with thin adhesive layer

Pugstaller, Robert; Wallner, Gernot M.

doi:10.1016/j.engfracmech.2021.108045

Cited by 9 publications

(5 citation statements)

References 17 publications

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“…The adhesive strength of the laminates was assessed by roll peel testing at 23, 100 and 140 • C. Laminates based on adhesives of higher EEW values exhibited better adherence performance below, and above, glass transition. A maximum strength of about 9 N/mm at 23 • C was obtained, which was in good agreement with data from the literature [3]. At 100 and 140 • C, roll peel strength dropped by 50 and 75%, respectively.…”

Section: Discussionsupporting

confidence: 91%

“…The debonding energy or strain energy release rate was calculated considering a simple beam theory approach. Specific details are given in [3].…”

Section: Characterization Of Raw Materials Coatings and Laminatesmentioning

confidence: 99%

“…Electrical steel laminates based on epoxy adhesive layers are of high relevance for the transformation of electric energy [1][2][3][4]. By the stacking and bonding of thin electrical steel sheets, eddy current losses are reduced and the efficiency of electric machines is raised [3]. Epoxy plies act as multifunctional separation layers providing electrical isolation and full-surface bonding.…”

Section: Introduction ¨υmentioning

confidence: 99%

“…Lamination and isolation of electrical steel with epoxy-based adhesives offers many advantages, but also a few drawbacks. Compared to classical joining methods like welding or interlocking, the high temperature performance of adhesively bonded laminates is limited [3].…”

Section: Introduction ¨υmentioning

confidence: 99%

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Effect of Epoxy Structure on Properties of Waterborne Coatings and Electrical Steel Laminates

et al. 2022

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Epoxy varnishes are of high relevance to advanced steel laminates for the transformation of electric energy. Structure–property correlations of epoxy varnishes, coil coatings and electrical steel laminates are poorly described. Hence, the main objective of this paper was to develop, implement and evaluate well-defined waterborne model epoxy varnishes for electrical steel laminates, and to elucidate structure–property correlations. Adhesives with systematically varied equivalent epoxy weight (EEW) based on bisphenol‑A‑diglycidyl ether (DGEBA) were investigated and used to formulate waterborne varnishes. Crosslinking agent dicyandiamide (DICY) was added in an over-stoichiometric ratio. The waterborne model varnishes were prepared by shear emulsification at elevated temperatures. The model varnishes in the A-stage were applied to electrical steel using a doctoral blade. At a peak metal temperature of 210 °C, the coatings were cured to the partly crosslinked B-stage. Coated steel sheets were stacked, laminated and fully cured to C-stage at 180 °C for 2 h. For laminates with an epoxy adhesive layer in the C-stage, glass transition temperatures (TG) in the range of 81 to 102 °C were obtained by dynamic mechanical analysis in torsional mode. Within the investigated EEW range, a negative linear correlation of EEW and TG was ascertained. Presumably, higher EEW of the varnish is associated with a less densely crosslinked network in the fully cured state. Roll peel testing of laminates at ambient and elevated temperatures up to 140 °C confirmed the effect of EEW. However, no clear correlation of roll peel strength and glass transition temperature was discernible. In contrast, fatigue fracture mechanics investigations revealed that hydroxyl functionality and crosslinking density were affecting the crack growth resistance of laminates in a contrary manner. The energy-based fracture mechanics approach was much more sensitive than monotonic peel testing.

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Section: Discussionsupporting

confidence: 91%

“…The debonding energy or strain energy release rate was calculated considering a simple beam theory approach. Specific details are given in [3].…”

Section: Characterization Of Raw Materials Coatings and Laminatesmentioning

confidence: 99%

Section: Introduction ¨υmentioning

confidence: 99%

Section: Introduction ¨υmentioning

confidence: 99%

See 2 more Smart Citations

Effect of Epoxy Structure on Properties of Waterborne Coatings and Electrical Steel Laminates

et al. 2022

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“…A group of AM techniques like stereolithography are based on curing of liquid resins [149]. Another group like laminated object manufacturing fabricates parts by joining sheet feedstock [150,151]. Yet other group melt powdered materials like selective laser sintering to obtain 3D parts [152].…”

Section: Raw Materials State For Am Processmentioning

confidence: 99%