PSI - Issue 25

E. Solfiti et al. / Procedia Structural Integrity 25 (2020) 420 – 429 E. Solfiti and F. Berto / Structural Integrity Procedia 00 (2019) 000–000

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(a)

(b)

(c)

Fig. 7: An example of the e ff ect of solid content on (a) loss tangent, (b) storage modulus and (c) loss modulus during flexural test. All the values are normalized by the solid content itself. Pictures by Chen and Chung (2013)

• tensile behavior is both elastic and plastic. Stress-strain curves are available but not easily fitted with known models. Tensile modulus and strength depend strongly on the density and the natural flake sizes. Their values are to be still well-investigated; • fracture behavior is due to crack and slippage among boundaries of the interlocked units. The strength is only due to the friction forces at the edges. The crack does not grow from a localized spot but in multiple locations close to the notch contemporaneously; • visco-elastic properties depend on the density. Higher the solid content and higher the sti ff ness contribution to the overall behavior. FG retain good loss tangent values and the dissipative sliding is provided by the relative displacement among the cell walls; • about the modeling Khelifa et al. (2018) showed the first attempt available in literature but it has to be supported by further testing. What is known from a mechanical point of view about FG is very partial and mostly related to the current needs of industrial applications. Thermal and electrical properties are of outstanding interest and have been better investigated, whereas some lacks have been noticed about stress and deformation e ff ects even in standard condition. No data are available except Dowell and Howard (1986) about high temperature tests. Fatigue damage is not investigated and only partial hysteresis cycles were observed in static compression. The only fractographs available are from Gu et al. (2002) and no crack growth observation have been developed yet.

References

Balima, F., Le Floch, S., San-Miguel, A., Lindner, P., Bruˆ let, A., Duclaux, L., Pischedda, V., 2014. Shear e ff ects on expanded graphite under uniaxial pressure: An in situ small angle neutron scattering study. Carbon 74, 54–62. doi: 10.1016/j.carbon.2014.03.002 .