PSI - Issue 26

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ScienceDirect

Procedia Structural Integrity 26 (2020) 187–198 Structural Integrity Procedia 00 (2019) 000–000 Structural Integrity Procedia 00 ( 19) 000–000

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© 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of MedFract1 organizers Abstract Flexible graphite (FG) is the last stage of compression of expanded graphite. Natural and highly crystalline graphite flakes are expanded and rolled together without any binder in order to shape foils of di ff erent thicknesses and densities. The result is an anisotropic but highly conductive material, with low strength and sti ff ness compared to common graphite, but gathering a collection of di ff erent peculiar properties. About mechanical field, FG is mostly used in sealing and gasketing applications due to its resilience and capability of dissipate energy during vibration. It also shows high resistance against chemical agents and can retain its struc tural integrity at temperature up to 2500 ◦ C in inert atmosphere. All the mechanical, electrical and thermal properties are strongly a ff ected by the inherent anisotropy that make it exploitable in thermal cooling, interface insulation, electromagnetic shielding and in electrical conduction components such as fuel cell electrodes. In this work the manufacturing process is summarized together with the e ff ect of density on strength and modulus and the experimental results found in literature among anisotropy, sti ff ness, thermal and electrical conductivity, specific heat and thermal expansion are reviewed together with some modeling approaches. 2020 The Authors. Published by Elsevier B.V. is is an open access article under the CC BY- C-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) r re ie unde responsibility of MedFract1 organizers. Keywords: Thermal conductivity;Thermal exspansion;Specific heat capacity The 1 st Mediterranean Conference on Fracture and Structural Integrity, MedFract1 A review on thermophysical properties of flexible graphite E. Solfiti a , F. Berto a a Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology, Richard Birkelands vei 2B, Trondheim, 7491, Norway Abstract Flexible graphite (FG) is the last stage of compression of expanded graphite. Natural and highly crystalline graphite flakes are expanded and rolled together without any binder in order to shape foils of di ff erent thicknesses and densities. The result is an anisotropic but highly conductive material, with low strength and sti ff ness compared to common graphite, but gathering a collection of di ff erent peculiar properties. About mechanical field, FG is mostly used in sealing and gasketing applications due to its resilience and capability of dissipate energy during vibration. It also shows high resistance against chemical agents and can retain its struc tural integrity at temperature up to 2500 ◦ C in inert atmosphere. All the mechanical, electrical and thermal properties are strongly a ff ected by the inherent anisotropy that make it exploitable in thermal cooling, interface insulation, electromagnetic shielding and in electrical conduction components such as fuel cell electrodes. In this work the manufacturing process is summarized together with the e ff ect of density on strength and modulus and the experimental results found in literature among anisotropy, sti ff ness, thermal and electrical conductivity, specific heat and thermal expansion are reviewed together with some modeling approaches. © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of MedFract1 organizers. Keywords: Thermal conductivity;Thermal exspansion;Specific heat capacity The 1 st Mediterranean Conference on Fracture and Structural Integrity, MedFract1 A review on thermophysical properties of flexible graphite E. Solfiti a , F. Berto a a Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology, Richard Birkelands vei 2B, Trondheim, 7491, Norway

1. Introduction 1. Introduction

Flexible graphite (FG) is a porous anisotropic material which substantially di ff ers from graphite from various aspects including ore origin place, manufacturing process and microstructure. As it will be shown hereafter, in some cases its properties resemble those of regular graphite but in others they can remarkably deviate. FG development dates back to the end of the 60’s [Shane et al. (1968)] and it results from a rolling compression of expanded graphite (EG) particles without any additive binder. Commercial FG commonly appears in the form of sheets (or foils, at lower thicknesses) ranging from 0.076 to 3 mm thickness and from 0.5 to 1.8 g / cm 3 in density; other shapes are available such as yarns and composite stacked arrangements. In some cases, mostly for scientific purposes, simple uniaxial Flexible graphite (FG) is a porous anisotropic material which substantially di ff ers from graphite from various aspects including ore origin place, manufacturing process and microstructure. As it will be shown hereafter, in some cases its properties resemble those of regular graphite but in others they can remarkably deviate. FG development dates back to the end of the 60’s [Shane et al. (1968)] and it results from a rolling compression of expanded graphite (EG) particles without any additive binder. Commercial FG commonly appears in the form of sheets (or foils, at lower thicknesses) ranging from 0.076 to 3 mm thickness and from 0.5 to 1.8 g / cm 3 in density; other shapes are available such as yarns and composite stacked arrangements. In some cases, mostly for scientific purposes, simple uniaxial

∗ Corresponding author. E.Solfiti Tel.: + 39-3405863109 E-mail address: emanuele.solfiti@ntnu.no (E. Solfiti) ∗ Corresponding author. E.Solfiti Tel.: + 39-3405863109 E-mail address: emanuele.solfiti@ntnu.no (E. Solfiti)

2452-3216 © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of MedFract1 organizers 10.1016/j.prostr.2020.06.022 2210-7843 © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of MedFract1 organizers. 2210-7843 © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of MedFract1 organizers.