Research

16 pages, 4745 KiB

Open AccessArticle

A Novel Technique for Substrate Toughening in Wood Single Lap Joints Using a Zero-Thickness Bio-Adhesive

by Shahin Jalali, Catarina da Silva Pereira Borges, Ricardo João Camilo Carbas, Eduardo André de Sousa Marques, Alireza Akhavan-Safar, Ana Sofia Oliveira Ferreira Barbosa, João Carlos Moura Bordado and Lucas Filipe Martins da Silva

Materials 2024, 17(2), 448; https://0-doi-org.brum.beds.ac.uk/10.3390/ma17020448 - 17 Jan 2024

Viewed by 549

Abstract

In contemporary engineering practices, the utilization of sustainable materials and eco-friendly techniques has gained significant importance. Wooden joints, particularly those created with polyurethan-based bio-adhesives, have garnered significant attention owing to their intrinsic environmental advantages and desirable mechanical properties. In comparison to conventional joining [...] Read more.

In contemporary engineering practices, the utilization of sustainable materials and eco-friendly techniques has gained significant importance. Wooden joints, particularly those created with polyurethan-based bio-adhesives, have garnered significant attention owing to their intrinsic environmental advantages and desirable mechanical properties. In comparison to conventional joining methods, adhesive joints offer distinct benefits such as an enhanced load distribution, reduced stress concentration, and improved aesthetic appeal. In this study, reference and toughened single-lap joint samples were investigated experimentally and numerically under quasi-static loading conditions. The proposed research methodology involves the infusion of a bio-adhesive into the wooden substrate, reinforcing the matrix of its surfaces. This innovative approach was developed to explore a synergetic effect of both wood and bio-adhesive. The experimentally validated results showcase a significant enhancement in joint strength, demonstrating an 85% increase when compared to joints with regular pine substrates. Moreover, the increased delamination thickness observed in toughened joints was found to increase the energy absorption of the joint. Full article

(This article belongs to the Special Issue Mechanical Properties and Application of Adhesive Materials)

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19 pages, 6080 KiB

Open AccessArticle

Mechanical Performance of Adhesive Connections in Structural Applications

by Marco Lamberti, Aurélien Maurel-Pantel and Frédéric Lebon

Materials 2023, 16(22), 7066; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16227066 - 07 Nov 2023

Cited by 2 | Viewed by 747

Abstract

Adhesive bonding is an excellent candidate for realising connections for secondary structures in structural applications such as offshore wind turbines and installations, avoiding the risk and associated welding problems. The strength of the adhesive layer is an important parameter to consider in the [...] Read more.

Adhesive bonding is an excellent candidate for realising connections for secondary structures in structural applications such as offshore wind turbines and installations, avoiding the risk and associated welding problems. The strength of the adhesive layer is an important parameter to consider in the design process it being lower than the strength capacity of the bonding material. The presence of defects in the adhesive materials undoubtedly influences the mechanical behaviour of bonded composite structures. More specifically, the reduction in strength is more pronounced as the presence of defects (voids) increases. For this reason, a correct evaluation of the presence of defects, which can be translated into damage parameters, has become essential in predicting the actual behaviour of the bonded joints under different external loading conditions. In this paper, an extensive experimental programme has been carried out on adhesively bonded connections subjected to Mode I and Mode II loading conditions in order to characterise the mechanical properties of a commercial epoxy resin and to define the damage parameters. The initial damage parameters of the adhesive layer have been identified according to the Kachanov–Sevostianov material definition, which is able to take into account the presence of diffuse initial cracking. Full article

(This article belongs to the Special Issue Mechanical Properties and Application of Adhesive Materials)

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16 pages, 3980 KiB

Open AccessEditor’s ChoiceArticle

A Numerical Model for Understanding the Development of Adhesion during Drying of Cellulose Model Surfaces

by Magdalena Kaplan and Sören Östlund

Materials 2023, 16(4), 1327; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16041327 - 04 Feb 2023

Viewed by 1113

Abstract

Adhesion is crucial for the development of mechanical properties in fibre-network materials, such as paper or other cellulose fibre biocomposites. The stress transfer within the network is possible through the fibre–fibre joints, which develop their strength during drying. Model surfaces are useful for [...] Read more.

Adhesion is crucial for the development of mechanical properties in fibre-network materials, such as paper or other cellulose fibre biocomposites. The stress transfer within the network is possible through the fibre–fibre joints, which develop their strength during drying. Model surfaces are useful for studying the adhesive strength of joints by excluding other parameters influencing global performance, such as geometry, fibre fibrillation, or surface roughness. Here, a numerical model describes the development of adhesion between a cellulose bead and a rigid surface using an axisymmetric formulation, including moisture diffusion, hygroexpansion, and cohesive surfaces. It is useful for studying the development of stresses during drying. A calibration of model parameters against previously published contact and geometry measurements shows that the model can replicate the observed behaviour. A parameter study shows the influence of cohesive and material parameters on the contact area. The developed model opens possibilities for further studies on model surfaces, with quantification of the adhesion during pull-off measurements. Full article

(This article belongs to the Special Issue Mechanical Properties and Application of Adhesive Materials)

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16 pages, 8358 KiB

Open AccessEditor’s ChoiceArticle

Creep Crack Growth Behavior during Hot Water Immersion of an Epoxy Adhesive Using a Spring-Loaded Double Cantilever Beam Test Method

by Kota Nakamura, Yu Sekiguchi, Kazumasa Shimamoto, Keiji Houjou, Haruhisa Akiyama and Chiaki Sato

Materials 2023, 16(2), 607; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16020607 - 08 Jan 2023

Cited by 2 | Viewed by 2339

Abstract

Double cantilever beam (DCB) tests were conducted by immersing the specimens in temperature-controlled water while applying a creep load using a spring. By introducing a data reduction scheme to the spring-loaded DCB test method, it was confirmed that only a single parameter measurement [...] Read more.

Double cantilever beam (DCB) tests were conducted by immersing the specimens in temperature-controlled water while applying a creep load using a spring. By introducing a data reduction scheme to the spring-loaded DCB test method, it was confirmed that only a single parameter measurement was sufficient to calculate the energy release rate (ERR). Aluminum alloy substrates bonded with an epoxy adhesive were used, and DCB tests were performed by changing the initial load values, spring constants, and immersion temperatures for two types of surface treatment. The initial applied load and spring constant had no effect on the ERR threshold. In contrast, the threshold decreased with the increasing immersion temperature, but even in the worst case, it was 15% of the critical ERR in the static tests. Using the creep crack growth relationship, it was revealed that there were three phases of creep immersion crack growth in the adhesive joints, and each phase was affected by the temperature. The spring-loaded DCB test method has great potential for investigating the combined effects of creep, moisture, and temperature, and this study has demonstrated the validity of the test method. The long-term durability of adhesive joints becomes increasingly important, and this test method is expected to become widespread. Full article

(This article belongs to the Special Issue Mechanical Properties and Application of Adhesive Materials)

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15 pages, 2747 KiB

Open AccessArticle

Self-Crosslinkable Pressure-Sensitive Adhesives from Silicone-(Meth)acrylate Telomer Syrups

by Mateusz Weisbrodt and Agnieszka Kowalczyk

Materials 2022, 15(24), 8924; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15248924 - 14 Dec 2022

Cited by 3 | Viewed by 1457

Abstract

In this study, a novel and environmentally friendly method for the preparation of photoreactive pressure-sensitive adhesives (PSAs) was demonstrated. Adhesive binders based on n-butyl acrylate, methyl methacrylate, acrylic acid, and 4-acryloyloxy benzophenone were prepared with a UV-induced telomerization process in the presence of [...] Read more.

In this study, a novel and environmentally friendly method for the preparation of photoreactive pressure-sensitive adhesives (PSAs) was demonstrated. Adhesive binders based on n-butyl acrylate, methyl methacrylate, acrylic acid, and 4-acryloyloxy benzophenone were prepared with a UV-induced telomerization process in the presence of triethylsilane (TES) as a telogen and acylphosphine oxide (APO) as a radical photoinitiator. The influence of TES (0–10 wt. parts) and APO (0.05–0.1 wt. parts/100 wt. parts of monomer mixtures) concentrations on the UV telomerization process kinetics was investigated using a photodifferential scanning calorimetry method and selected physicochemical features of the obtained silicone-(met)acrylate telomeric syrups (K-value, solid content, glass-transition temperature, and dynamic viscosity), as well as properties of the obtained PSAs (T_g, adhesion, tack, and cohesion), were studied. An increase in TES content caused a significant decrease in the T_g values (approx. 10 °C) and K-value (up to approximately 25 a.u.) of the dry telomers, as well as the dynamic viscosity of the telomeric syrups. PSAs were obtained through UV irradiation of thin polymer films consisting only of silicone-(meth)acrylate telomer solutions (without the use of additional chemical modifiers or of a protective gas atmosphere and protective layers). PSAs were characterized by very good adhesion (12.4 N/25 mm), cohesion at 20 °C (>72 h) and 70 °C (>72 h), and low glass-transition temperature (−25 °C). Full article

(This article belongs to the Special Issue Mechanical Properties and Application of Adhesive Materials)

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25 pages, 5700 KiB

Open AccessEditor’s ChoiceArticle

Nonlinear Analytical Procedure for Predicting Debonding of Laminate from Substrate Subjected to Monotonic or Cyclic Load

by Marco Lamberti, Francesco Ascione, Annalisa Napoli, Ghani Razaqpur and Roberto Realfonzo

Materials 2022, 15(23), 8690; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15238690 - 06 Dec 2022

Cited by 5 | Viewed by 1407

Abstract

The bonding of steel/fiber-reinforced polymer (SRP/FRP) laminate strips to concrete/masonry elements has been found to be an effective and efficient technology for improving the elements’ strength and stiffness. However, premature laminate–substrate debonding is commonly observed in laboratory tests, which prevents the laminate from [...] Read more.

The bonding of steel/fiber-reinforced polymer (SRP/FRP) laminate strips to concrete/masonry elements has been found to be an effective and efficient technology for improving the elements’ strength and stiffness. However, premature laminate–substrate debonding is commonly observed in laboratory tests, which prevents the laminate from reaching its ultimate strength, and this creates uncertainty with respect to the level of strengthening that can be achieved. Therefore, for the safe and effective application of this technology, a close estimate of the debonding load is necessary. Towards this end, in this paper, a new, relatively simple, semi-analytic model is presented to determine the debonding load and the laminate stress and deformation, as well as the interfacial slip, for concrete substrates bonded to SRP/FRP and subjected to monotonic or cyclic loading. In the model, a bond-slip law with a linearly softening branch is combined with an elasto-plastic stress-strain relationship for SRP. The model results are compared with available experimental data from single-lap shear tests, with good agreement between them. Full article

(This article belongs to the Special Issue Mechanical Properties and Application of Adhesive Materials)

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27 pages, 4917 KiB

Open AccessArticle

Influence of Physical Modification of the Adhesive Composition on the Strength Properties of Aerospace Aluminum Alloy Sheet Adhesive Joints

by Izabela Miturska-Barańska, Anna Rudawska and Elżbieta Doluk

Materials 2022, 15(21), 7799; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15217799 - 04 Nov 2022

Cited by 3 | Viewed by 1653

Abstract

One of the most important design factors in the constitution of adhesive joints is the correct choice of adhesive. Currently, there is a full range of options on the commercial market in this regard, but there is increasing research into modifying adhesives for [...] Read more.

One of the most important design factors in the constitution of adhesive joints is the correct choice of adhesive. Currently, there is a full range of options on the commercial market in this regard, but there is increasing research into modifying adhesives for specific engineering applications. The aim of this study was to analyze the effect of physical modification with fillers on the properties of the adhesive composition and the adhesive joints. The adhesives used in the study were a composition of Epidian 5 epoxy resin and PAC curing agent modified with 1% montmorillonite, 5% calcium carbonate and 20% activated carbon. The adhesive compositions in the cured state were subjected to strength tests and SEM and DSC analyses. Using these compositions, adhesive joints of EN AW 2024 T3 aluminum alloy sheets were also made. The tests carried out showed that, due to the use of different fillers, their effects on certain properties of the adhesive compositions are different types. It was shown that physical modification of the adhesive composition does not always result in positive effects. The study also attempted to determine the correlation between the properties of the adhesive compositions in the cured state and the strength of the adhesive joints. Full article

(This article belongs to the Special Issue Mechanical Properties and Application of Adhesive Materials)

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18 pages, 2784 KiB

Open AccessArticle

Adhesive Joint Degradation Due to Hardener-to-Epoxy Ratio Inaccuracy under Varying Curing and Thermal Operating Conditions

by Jakub Szabelski, Robert Karpiński, Józef Jonak and Mariaenrica Frigione

Materials 2022, 15(21), 7765; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15217765 - 03 Nov 2022

Cited by 4 | Viewed by 1212

Abstract

This paper presents the results of an experimental study of adhesive joint strength with consideration of the inaccuracy of the hardener dosage, in the context of evaluating the degradation of joints when used either at ambient or elevated temperatures. The butt joint strength [...] Read more.

This paper presents the results of an experimental study of adhesive joint strength with consideration of the inaccuracy of the hardener dosage, in the context of evaluating the degradation of joints when used either at ambient or elevated temperatures. The butt joint strength characteristics were assessed for two types of adhesives—rigid and flexible—and two curing scenarios—with and without heat curing. An excess hardener was shown to be significantly more unfavourable than its deficiency, which can ultimately be considered as a recommendation for forming epoxy adhesive joint assemblies. In order to fully understand the relationship between the analysed mechanical properties of the material and the influence of component ratio excesses and heating, a process of fitting basic mathematical models to the obtained experimental data was also performed. Full article

(This article belongs to the Special Issue Mechanical Properties and Application of Adhesive Materials)

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