Thermal cycling of cold-pressed PTFE compacts: Reversible and irreversible behavior

Gabriel Guenoun (1, 2, 3) , Jean-Yvon Faou (1) , Gilles Regnier (2) , Nicolas Schmitt (3) , Stéphane Roux (3)

1 SGR - Saint-Gobain Recherche
2 PIMM - Laboratoire Procédés et Ingénierie en Mécanique et Matériaux
3 LMT - Laboratoire de Mécanique et Technologie

Cold uniaxial pressed PTFE compacts were subjected to thermal cycles of increasing maximum temperature below melting temperature, and thermal expansion was followed in both the compaction and transverse directions. The measurements reveal that thermal expansion consists of two distinct contributions: i) an irreversible part that is controlled only by the maximum temperature experienced by the sample, and ii) a reversible, or thermo-elastic, part that is observed while cycling below the maximum temperature. Moreover, both of these thermal strains exhibit marked anisotropy, resulting from the cold oedometric compaction of the sample. A quantitative analysis of these eigenstrains is proposed, following a formal analogy with elasto-plasticity. Finally, it is shown that such behavior is specific to cold-pressed compacts as sintered samples exhibit isotropic and purely reversible thermo-elastic behavior.

Mots clés: Residual stresses; Irreversible behavior; Anisotropy; PTFE; Dilatometry; Thermal cycle

Domaines: Matériaux

Gabriel Guenoun, Jean-Yvon Faou, Gilles Regnier, Nicolas Schmitt, Stéphane Roux. Thermal cycling of cold-pressed PTFE compacts: Reversible and irreversible behavior. Polymer Testing, 2019, 75, pp.99-106. ⟨10.1016/j.polymertesting.2019.01.018⟩. ⟨hal-02058007⟩