Application of High Frequency Dielectric Spectroscopy for the Assessment of Durability of Adhesively Bonded Composite Structures

1999 ◽  
Author(s):  
P. Boinard ◽  
R. A. Pethrick ◽  
W. M. Banks
Keyword(s):  
Mechanical Properties ◽  
Carbon Fibre ◽  
High Frequency ◽  
Composite Structures ◽  
Adhesive Layer ◽  
Dielectric Study ◽  
Adhesively Bonded ◽  
Wide Range ◽  
The Matrix ◽  
Bonded Composite

Abstract Composites materials, especially adhesively bonded structures are being used in a wide range of applications, including situations where they become exposed to high levels of moisture. Ingress of moisture into a polymeric material will in general lead to changes in its mechanical properties usually associated with plasticisation effects. In bonded composite structures, water ingress can influence not only the mechanical properties of the matrix but also those of the matrix-fibre and adhesive-adherent interfaces. Over the last ten years, the application of high-frequency dielectric techniques to the characterisation of the integrity and durability of adhesively bonded metallic structures has been extensively investigated by the coauthors. In general, a bonded structure resembles a wave-guide in which the adhesive layer is the dielectric. Changes in the characteristics as a function of time of exposure to the environment can be used to monitor the ageing of such structures. This paper discusses the application of the principles to the study of carbon fibre reinforced plastics (CFRP) adhesively bonded composite structures. Carbon fibre is in general less conductive than aluminium material. However, it is sufficiently conductive to sustain the propagation of high-frequency dielectric signals. The effect of changes in the surface alignment and subsequent bulk orientation of carbon fibres on the dielectric propagation has been investigated. The ingress of moisture in the raw materials and in the joint structure is presented. The high-frequency time domain response (TDR) analysis allows the integrity of the structure to be explored and a good correlation is shown between TDR analysis and gravimetric results. This study indicates that the success obtained in the application of high frequency dielectric measurements to adhesively bonded aluminium structures is also applicable to CFRP bonded structures. The dielectric study not only indicates a new way to assess the state of such a structure but is also producing new insights into the application of TDR measurement to non-isotropic materials.

scholarly journals Defects and uncertainties of adhesively bonded composite joints

2021 ◽  
Vol 3 (9) ◽  
Author(s):  
Sadik Omairey ◽  
Nithin Jayasree ◽  
Mihalis Kazilas
Keyword(s):  
Composite Materials ◽  
Composite Structures ◽  
Production Efficiency ◽  
Adhesive Bonding ◽  
Detection Methods ◽  
Bonded Joints ◽  
Adhesively Bonded ◽  
Adhesively Bonded Joints ◽  
Wide Range ◽  
Bonded Composite

AbstractThe increasing use of fibre reinforced polymer composite materials in a wide range of applications increases the use of similar and dissimilar joints. Traditional joining methods such as welding, mechanical fastening and riveting are challenging in composites due to their material properties, heterogeneous nature, and layup configuration. Adhesive bonding allows flexibility in materials selection and offers improved production efficiency from product design and manufacture to final assembly, enabling cost reduction. However, the performance of adhesively bonded composite structures cannot be fully verified by inspection and testing due to the unforeseen nature of defects and manufacturing uncertainties presented in this joining method. These uncertainties can manifest as kissing bonds, porosity and voids in the adhesive. As a result, the use of adhesively bonded joints is often constrained by conservative certification requirements, limiting the potential of composite materials in weight reduction, cost-saving, and performance. There is a need to identify these uncertainties and understand their effect when designing these adhesively bonded joints. This article aims to report and categorise these uncertainties, offering the reader a reliable and inclusive source to conduct further research, such as the development of probabilistic reliability-based design optimisation, sensitivity analysis, defect detection methods and process development.

scholarly journals Influence of Alumina Nanofibers Sintered by the Spark Plasma Method on Nickel Mechanical Properties

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 548 ◽  
Author(s):  
Leonid Agureev ◽  
Valeriy Kostikov ◽  
Zhanna Eremeeva ◽  
Svetlana Savushkina ◽  
Boris Ivanov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Elastic Modulus ◽  
Strength Properties ◽  
Alumina Nanoparticles ◽  
Metal Powders ◽  
Wide Range ◽  
The Matrix ◽  
Spark Plasma ◽  
Average Size

The article presents the study of alumina nanoparticles’ (nanofibers) concentration effect on the strength properties of pure nickel. The samples were obtained by spark plasma sintering of previously mechanically activated metal powders. The dependence of the grain size and the relative density of compacts on the number of nanofibers was investigated. It was found that with an increase in the concentration of nanofibers, the average size of the matrix particles decreased. The effects of the nanoparticle concentration (0.01–0.1 wt.%) on the elastic modulus and tensile strength were determined for materials at 25 °C, 400 °C, and 750 °C. It was shown that with an increase in the concentration of nanofibers, a 10–40% increase in the elastic modulus and ultimate tensile strength occurred. A comparison of the mechanical properties of nickel in a wide range of temperatures, obtained in this work with materials made by various technologies, is carried out. A description of nanofibers’ mechanisms of influence on the structure and mechanical properties of nickel is given. The possible impact of impurity phases on the properties of nickel is estimated. The tendency of changes in the mechanical properties of nickel, depending on the concentration of nanofibers, is shown.

An experimental–numerical investigation of hydrothermal response in adhesively bonded composite structures

2015 ◽  
Vol 73 ◽  
pp. 176-185 ◽  
Author(s):  
Roohollah Sarfaraz ◽  
Luis P. Canal ◽  
Georgios Violakis ◽  
John Botsis ◽  
Véronique Michaud ◽  
...  
Keyword(s):  
Numerical Investigation ◽  
Composite Structures ◽  
Adhesively Bonded ◽  
Bonded Composite

scholarly journals Quasi-Static Tests of Hybrid Adhesive Bonds Based on Biological Reinforcement in the Form of Eggshell Microparticles

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1391 ◽  
Author(s):  
Viktor Kolář ◽  
Miroslav Müller ◽  
Rajesh Mishra ◽  
Anna Rudawska ◽  
Vladimír Šleger ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cyclic Loading ◽  
Service Life ◽  
Adhesive Layer ◽  
Maximum Load ◽  
Adhesive Bonds ◽  
Static Tests ◽  
Static Test ◽  
The Matrix ◽  
Positive Effect

The paper is focused on the research of the cyclic loading of hybrid adhesive bonds based on eggshell microparticles in polymer composite. The aim of the research was to characterize the behavior of hybrid adhesive bonds with composite adhesive layer in quasi-static tests. An epoxy resin was used as the matrix and microparticles of eggshells were used as the filler. The adhesive bonds were exposed to cyclic loading and their service life and mechanical properties were evaluated. Testing was performed by 1000 cycles at 5–30% (165–989 N) and 5–70% (165–2307 N) of the maximum load of the filler-free bond in the static test. The results of the research show the importance of cyclic loading on the service life and mechanical properties of adhesive bonds. Quasi-static tests demonstrated significant differences between measured intervals of cyclic loading. All adhesive bonds resisted 1000 cycles of the quasi-static test with an interval loading 5–30%. The number of completed quasi-static tests with the interval loading 5–70% was significantly lower. The filler positively influenced the service life of adhesive bonds at a higher amount of quasi-static tests, i.e., the safety of adhesive bonds increased. The filler had a positive effect on adhesive bonds ABF2, where the strength significantly increased up to 20.26% at the loading of 5–30% against adhesive bonds ABF0. A viscoelasticity characteristic (creep) of the adhesive layer occurred at higher values of loading, i.e., between loading 5–70%. The viscoelasticity behavior did not occur at lower values of loading, i.e., between loading 5–30%.

Effect of Adhesive Layer Thickness on the Shear Strength of Adhesively Bonded Steel Joints in Wet Environment

2016 ◽  
Vol 836 ◽  
pp. 78-82 ◽  
Author(s):  
Sugiman ◽  
Ilham Akbar ◽  
Emmy Dyah Sulistyowati ◽  
Paryanto Dwi Setyawan
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Adhesive Layer ◽  
Static Strength ◽  
Adhesive Joints ◽  
Deionized Water ◽  
Adhesively Bonded ◽  
Moist Environment ◽  
Adhesive Thickness ◽  
Steel Joints

The paper presents the static strength of adhesively bonded steel joints aged in deionized water at a temperature of 60°C for 15 days at various adhesive thicknesses from 0.1 mm to 0.5 mm. Water uptake and the bulk adhesive tensile properties after aged in the same environment as the joints were also presented. It has been shown that water diffusion into the adhesive is non Fickian. The absorbed water in the adhesive significantly decreases the mechanical properties and it affects the static strength of the bonded steel joints. The effect of water is shown to be significant when the adhesive thickness is thicker than 0.2 mm as the static strength decreases sharply. This information is useful when designing the adhesive joints using thick adhesive layer exposed in moist environment.

Progress in the Development of a Mechanical Properties Microprobe

MRS Bulletin ◽  
1986 ◽  
Vol 11 (5) ◽  
pp. 15-21 ◽  
Author(s):  
W. C. Oliver
Keyword(s):  
Mechanical Properties ◽  
Mechanical Response ◽  
Quantitative Information ◽  
General Term ◽  
Strength Properties ◽  
Physical Measurements ◽  
Wide Range ◽  
The Matrix ◽  
Recent Developments ◽  
Skilled Practitioner

A mechanical properties microprobe is an exciting concept. A system with the ability to evaluate the mechanical response of a sample with submicron spacial resolution would have an extremely wide range of applications. Recent developments in hardware and understanding have placed this goal within our grasp.In 1971, J.J.Gilman wrote the following in his article, “Hardness—A Strength Microprobe”:“Hardness measurements are at once among the most maligned and the most magnificent of physical measurements. Maligned because they are often misinterpreted by the uninitiated, and magnificent because they are so efficient in generating information for the skilled practitioner. They can quickly yield quantitative information about the elastic, anelastic, plastic, viscous, and fracture properties of a great variety of both isotropic and anisotropic solids. The tools that are used are simple and the sample sizes that are needed are typically small, sometimes submicroscopic. This makes it unnecessary to have large specimens in order to measure strength properties and makes it possible to measure the properties of various microscopic particles within the matrix phase of a polyphase metal, mineral, or ceramic material. This is why hardness may be considered to be a strength microprobe.”These statements are worth repeating for two reasons. First, they point out the largely untapped potential for microin-dentation tests to improve our understanding of the mechanical properties of materials. Second, it is the first mention of hardness tests in the context of a strength microprobe. In this article the more general term of microindentation tests will be used, since hardness is only one of many properties that can be measured with such tests. In addition, the term mechanical properties microprobe (MPM) will be used rather than strength microprobe-again, to note the wide variety of properties that can be measured.

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