Mechanical properties of thermosets |
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Authors: | A. Tcharkhtchi S. Faivre L. E. Roy J. P. Trotignon J. Verdu |
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Affiliation: | (1) ENSAM, 151, Boulevard de l'Hopital, 75013 Paris, France |
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Abstract: | The tensile properties of a DGEBA (diglycidylether of bisphenol A)-norbornene anhydride network (Tg130±5 °C), were studied in the range (220 K-Tg); 4×10–4 to 14×10–3S–1. The viscoelastic spectrum (1 Hz) reveals a low transition at 220 K. The bulk modulus is practically constant between 200 K andTg — 20 K. The Poisson's ratio increases very slowly untilTg — 30 K. Then it increases rapidly to reach its asymptotic value (0.5) near toTg. The tensile (E) and shear (G) moduli display the classical behaviour linked to viscoelasticity. Plastic yielding occurs atT 80 °C, the elongation at yield is almost temperature and strain rate independent (G3y = 0.035), whereas the yield stress obeys Kambour's relationship: y = 1.1 (Tg —T) and Eyring's law (activation volume = 914cm3mol–1). Physical ageing at 120 °C strongly affects the yield stress and the ductility. The maximum draw ratio, obtained atT Tg, is RC = 1.35, which seems to be consistent with the network's crosslink density. |
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