Browsing by Author "Gharavian, Somayeh"

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    Carbon nanotube embedded adhesives for real-time monitoring of adhesion failure in high performance adhesively bonded joints
    (Springer Nature, 2020-10-08) Bregar, Tadej; An, Donglan; Gharavian, Somayeh; Burda, Marek; Durazo-Cardenas, Isidro; Thakur, Vijay Kumar; Ayre, David; Słoma, Marcin; Hardiman, Mark; McCarthy, Conor; Nezhad, Hamed Yazdani
    Carbon nanotubes (CNTs) embedded polymers are of increasing interest to scientific and industrial communities for multi-functional applications. In this article, CNTs have been introduced to high-strength epoxy adhesive for enabling in-situ strain sensing in adhesively bonded aluminium-to-aluminium single-lap joints to accurately indicate the onset and propagation of adhesion failure to the evolution of piezo-resistivity in varying mechanical loads. The CNT modified adhesive in bonded joints and the CNT modified adhesive alone have been tested under monothonic and cyclic tensile loads up to ultimate failure. The changes in the piezo-resistivity induced by the CNTs have been monitored in situ with respect to loading. A novel interpretation method has been developed for progressive, instantaneous adhesion failure estimation under cyclic tensile stresses from a resistivity baseline. The method indicates that the in-situ resistivity changes and the rate of the changes with strain, i.e. sensitivity, strongly correlate with the adhesion failure progression, irrespective of the CNT dispersion quality. Moreover, the effect of bond thickness on the evolution of piezo-resistivity and adhesion failure have been studied. It was observed that relatively thin adhesive bonds (0.18mm thickness), possessing higher CNT contact points than thick bonds (0.43mm thicknes), provide 100 times higher sensitivity to varying cyclic loads
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    Data underpinning the paper: 'Development and testing of carbonaceous tin-based solder achieving unprecedented joint performance Item'
    (Cranfield University, 2021-06-21 12:53) Hawi, Sara; Gharavian, Somayeh; Burda, Marek; Goel, Saurav; Lotfian, Saeid; Khaleque, Tasnuva; Yazdani Nezhad, Hamed
    The paper shows that the suitable addition of carbon nanomaterials to a tin-based solder material matrix results in two fold strength of soldered joints.
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    Development of carbonaceous tin-based solder composite achieving unprecedented joint performance
    (Springer, 2021-12-30) Hawi, Sara; Gharavian, Somayeh; Burda, Marek; Goel, Saurav; Lotfan, Saeid; Khaleque, Tasnuva; Yazdani Nezhad, Hamed
    Weight reduction and improved strength are two common engineering goals in the joining sector to benefit transport, aerospace, and nuclear industries amongst others. Here, in this paper, we show that the suitable addition of carbon nanomaterials to a tin-based solder material matrix (C-Solder® supplied by Cametics Ltd.) results in two-fold strength of soldered composite joints. Single-lap shear joint experiments were conducted on soldered aluminium alloy (6082 T6) substrates. The soldering material was reinforced in different mix ratios by carbon black, graphene, and single-walled carbon nanotubes (SWCNT) and benchmarked against the pristine C-solder®. The material characterisation was performed using Vickers micro-indentation, differential scanning calorimetry and nano-indentation, whereas functional testing involved mechanical shear tests using single-lap aluminium soldered joints and creep tests. The hardness was observed to improve in all cases except for the 0.01 wt.% graphene reinforced solders, with 5% and 4% improvements in 0.05 carbon black and SWCNT reinforced solders, respectively. The maximum creep indentation was noted to improve for all solder categories with maximum 11% and 8% improvements in 0.05 wt.% carbon black and SWCNT reinforced ones. In general, the 0.05 wt.% nanomaterial reinforced solders promoted progressive cohesion failure in the joints as opposed to instantaneous fully de-bonded failure observed in pristine soldered joints, which suggests potential application in high-performance structures where no service load induced adhesion failure is permissible (e.g. aerospace assemblies). The novel innovation developed here will pave the way to achieving high-performance solder joining without carrying out extensive surface preparations.
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    Strain self-sensing tailoring in functionalised carbon nanotubes/epoxy nanocomposites in response to electrical resistance change measurement
    (SSRN, 2020-10-26) An, Donglan; Nourry, Jim; Gharavian, Somayeh; Thakur, Vijay Kumar; Aria, Adrianus Indrat; Durazo-Cardenas, Isidro; Khaleque, Tasnuva; Nezhad, Hamed Yazdani
    Carbon nanotubes (CNTs) are inherently multifunctional, conductive and possess piezo-resistive characteristics. Aiming at the multi-functionality of materials, nanocomposites made of epoxy resin with embedded CNTs are a promising solution for strain self-sensing applications. A critical parameter to achieve repeatable and reliable measure is the CNTs dispersion state in the resin. This study investigated the effect of CNTs concentration (0.01 wt% and 0.1 wt%), with different loading of surfactant Triton X-100, (0.0%, 0.2%, 0.5% and 1.0%) on strain sensing in terms of sensitivity and linearity based on electrical resistance data. The CNTs were synthesised directly using an injection floating catalyst chemical vapor deposition (ICCVD) process and their quality was characterised by Raman spectroscopy and scanning electron microscopy. Only the epoxy modified with 0.1 wt% CNTs exhibited sufficient piezo-resistivity for the resistance measurements, and those with 0.01 wt% CNTs did not show sufficiently measurable conductivity so were excluded in our study, since their CNTs were highly entangled, and conductive network failed to be established. It was observed that, with 0.1 wt% CNTs, adding 0.5% content of the surfactant improved gauge factor. With more content of the surfactant (1.0 %), surprisingly, we observed a drop of gauge factor by the order of two. Therefore, by comparing the conductivity change between 1.0% and 0.5% surfactant, we postulated that the relatively high content surfactant has reached critical micelle concentration, and negatively affects CNTs dispersion state. The research presented in this article shows that moderate content of surfactant could improve piezo-resistivity gauge factor while excessive surfactant could cause adverse effect.
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    Underpinning Data for Article: Carbon nanotube embedded adhesives for real-time monitoring of adhesion failure in high performance adhesively bonded joints
    (Cranfield University, 2020-09-25 19:16) Yazdani Nezhad, Hamed; Bregar, Tadej; An, Donglan; Gharavian, Somayeh; Burda, Marek; Durazo-Cardenas, Isidro; Kumar, Vijay; Ayre, David; Sloma, Marcin; Hardiman, Mark; McCarthy, Conor
    The underpinning data for Research Article on Carbon nanotube embedded adhesives for real-time monitoring of adhesion failure in high performance adhesively bonded joints