The influence of curing conditions on the strength of adhesive joints

Frigione

2021

Materials

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The effects of aging exposures to three non-saline aqueous environments on the compressive mechanical properties of a calcium carbonate-filled bisphenolic epoxy adhesive, cold-cured with the addition of two curing agents suitable for the cure at ambient temperature (i.e., Mannich base and triethylenetetramine), were assessed. The amount of the added filler (CaCO3) varied from 1 to 3 g per 100 g of resin; the immersion times in each of the selected medium varied from 1 to 10 months. It was found that the mechanical properties measured in compression mode on cylindrical specimens of unfilled and CaCO3-loaded epoxy were scarcely influenced by the kind of curing agent employed; only the compressive modulus was limitedly affected by this parameter. Referring to the behavior when aged in water, the CaCO3-filled epoxies displayed noticeable growths in modulus, small reductions in strength, and limited variations in strain, with a certain influence of the exposure time, especially when comparing the properties at the lowest time with those at medium–long times. On the basis of the results of statistical MANOVA analysis, it can be concluded that among the compositional factors (i.e., the type of curing agent employed to cure the epoxy compounds and the micro-filler content), only the amount of CaCO3 filler significantly affects the compressive modulus.

Section: Methodsmentioning

confidence: 99%

Cold-Cured Bisphenolic Epoxy Adhesive Filled with Low Amounts of CaCO3: Effect of the Filler on the Durability to Aqueous Environments

Frigione

2021

Materials

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“…The different formulations placed in the moulds were subjected to a single-stage cure process carried out at an ambient temperature of 22 ± 1 • C, with relative humidity of 24 ± 4%. The curing time was 7 days, as suggested by suppliers and experienced in previous studies [5,8,14]. After this period, the specimens were demoulded and milled, in order to rectify the bases of cylindrical specimens.…”

Section: Characteristic Propertiesmentioning

confidence: 99%

Aging Effects of Aqueous Environment on Mechanical Properties of Calcium Carbonate-Modified Epoxy Resin

Frigione

2020

Polymers

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The purpose of this study was to assess the effects of different aqueous environments (i.e., demineralised, distilled and spring water) on the mechanical properties of a cold-cured bisphenolic epoxy resin modified with the addition of calcium carbonate filler, typically employed as structural adhesive. The parameters selected for the analysis have been; the kind of curing agent employed to cure the epoxy resin at ambient temperature (i.e., Mannich base and triethylenetetramine); the load of calcium carbonate added to liquid epoxy (i.e., from 1 to 3 g per 100 g of resin) and; the duration of the exposure to the different aging conditions (i.e., from 1 to 10 months). Cylindrical specimens of calcium carbonate-modified epoxy systems were tested in compression mode, before and after each of the aging regimes. The effect of the selected curing agents is very small, and they are both suitable for a cure at ambient temperature, on the unfilled epoxy on compressive maximum strength and strain at break; the choice of the hardener affects instead the compressive modulus. The CaCO3 amount was demonstrated to have a significant effect on the mechanical characteristics of un-aged epoxy systems, leading to growth in compressive modulus and maximum strength with reductions in strain at break. Generally speaking, the aging time noticeably affects the compressive properties of calcium carbonate-modified epoxies while almost negligible is the kind of water employed in each exposure regime. Notwithstanding the adverse effects of an aqueous environment on compressive mechanical properties of CaCO3-filled epoxies, these systems keep compressive modulus and maximum strength greater than, and close to, respectively, the same characteristics measured on unaged unfilled control epoxies, demonstrating the positive effect of the addition of this kind of filler to epoxy-based structural adhesives, especially with the addition of 2 and 3 g of CaCO3 per 100 g resin. The results obtained in this study demonstrated that it is possible to contrast the detrimental effects observed in cold-cured epoxy-based structural adhesives due to their aging in water upon the addition of limited amounts (particularly at 2 and 3 g per 100 g resin) of a cheap CaCO3 filler.

“…The properties of the cured epoxy adhesive compositions have been determined in accordance with DIN EN ISO 527-1 standard, using a Zwick/ Roell Z150 testing machine. These properties were obtained during the tests presented in works [37,38].…”

Section: Surface Preparationmentioning

confidence: 99%

Comparison of the adhesive joints’ strength of the similar and dissimilar systems of metal alloy/polymer composite

2019

Appl Adhes Sci

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Bonding technology is one of the most popular methods of joining various constructional materials [1-3]. It plays a vital role in production of different types of machines and tools [2]. This fact results from numerous advantages of the adhesive joints. The most important ones include the capacity of joining construction materials of different physical and chemical properties [4-6], as well as of significantly different sizes (e.g. thickness) [4, 7-9]. A lot of advantages of the adhesive joints have contributed to the fact that they are widely used in aviation [8, 10-12], aeronautics [13] and automotive [14, 15]. One of the most important advantages is the ability to make dissimilar joints [5, 16-18]. He and Ge [4] tested the effect of similar versus dissimilar assembled adherends of adhesively bonded composite joints, on the dynamic strength of single-lap. Pinto et al. [16] investigated the tensile strength of single-lap joints between similar and dissimilar adherends (included polyethylene (PE), polypropylene (PP), carbon-epoxy (CFRP), and glass-polyester (GFRP) composites) bonded with an acrylic adhesive.