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Etude du vieillissement thermique d’un jonc pultrudé en matériau composite

Abstract : This thesis is devoted to the study of thermal ageing and lifetime prediction of a composite rod used to stiffen electrical overhead power lines. The operating temperature of the wire is usually ranged between 80 and 90°C and, during maintenance, temperature can rise up to 220°C for short durations. Microstructural analysis of radial composite cross-sections after ageing between 160 and 220°C in air evidences its damage. When the epoxy matrix is under-crosslinked, the damage consists in a spontaneous cracking (due to stresses induced by the chemical shrinkage of the matrix) followed by the thermal oxidation of the rod core. However, when the matrix is better crosslinked, this damage is replaced by the formation and accumulation of microcavities of gases in the rod core, resulting from the matrix thermolysis. Eventually, these microcavities get connected to form wide apparent cracks. This degradation leads to the progressive decrease of the elastic modulus and, beyond a critical damage (porosities, cracks) fraction, a catastrophic fall of fracture properties. Based on these results, microstructure/properties relationships are established. Complementary tests by thermogravimetry coupled with high resolution mass spectrometry are carried on neat matrix films between 160 and 240°C under inert atmosphere to elucidate the thermolysis mechanism and the origin of the cavitation. The decomposition of unstable linkages in the epoxy network leads to the formation of three major volatile organic compounds including water. When the concentration of this later exceeds its solubility threshold in the matrix, the first microcavities appear. Based on these results, a mechanistic scheme and a kinetic model of thermolysis are proposed and successfully checked by gravimetry.
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Submitted on : Tuesday, May 19, 2020 - 4:01:35 AM
Last modification on : Wednesday, September 28, 2022 - 5:56:28 AM


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  • HAL Id : tel-02612214, version 1


Maéva Serror. Etude du vieillissement thermique d’un jonc pultrudé en matériau composite. Autre. Ecole nationale supérieure d'arts et métiers - ENSAM, 2013. Français. ⟨NNT : 2013ENAM0042⟩. ⟨tel-02612214⟩



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