PSI - Issue 26

E. Solfiti et al. / Procedia Structural Integrity 26 (2020) 187–198 E. Solfiti and F. Berto / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 6: Temperature dependence of FG specific heat capacity c p : 1. Butland and Maddison (1973), 2. Picard et al. (2006), 3. Lutcov et al. (1970), 4. Bonnissel et al. (2001), 5. Brooks and Bingham (1968), 6. Davis et al. (2001), 7. Grafoil ® , 8. Sigraflex ® .

stressed in a large extent. α T along the out-of-plane direction instead reaches values beyond 30 · 10 − 6 K − 1 . In Grafoil ® is suggested that in a first range of temperature up to 1000 ◦ C the foil shrinks (negative α T ) due to relaxation of residual stresses of compression and then slightly expands when the temperature e ff ect dominates. α T of both polycrystalline graphite and PG has a stable plateau approximately from room temperature up to beyond 1000 ◦ C and this might be resembled by FG in the same range. The similarities already shown among FG and other graphites induce to think about a monotonic increase of FG thermal expansion along with temperature. Copper and aluminum are isotropic and their thermal expansion is markedly higher than that of FG in the in-plane direction. Indeed, it has been shown in comparison with α T in the out-of-plane direction in figure 7b. The trend is more similar to that of graphite with a fast increase at low temperatures followed by a relatively lower slope in the region where graphite (and apparently FG) shows the plateau.

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Fig. 7: Temperature dependence of coe ffi cient of thermal expansion α T : 1. Kellett and Richards (1964), 2. Harrison (1977), 3. Bailey and Yates (1970), 4. Papyex ® , 5. Sigraflex ® , 6. Grafoil ® , 7. Morgan (1972), 8. Hahn (1970), 9. Otte et al. (1963). For polycrystalline graphite the symbol ⊥ is intended as perpendicular to extrusion direction.