The heat build-up and stress heterogeneity effects on PE

Lili Wan (1) , Lucien Laiarinandrasana (1) , C Ovalle (1)

1 CDM - Centre des Matériaux

Semi-crystalline polymers are attractive for various applications because they have a good compromise between weight, mechanical properties and recyclability. When submitted to static or cyclic loading, semicrystalline polymers exhibit deformation and damage mechanisms generally accompanied by temperature evolution, related with the conversion of plastic work into dissipative heat [1, 2]. Several mechanical models has been developed but commonly, for simplification reasons, thermomechanically uncoupled. An over-estimation of components lifetime is expected as the heat build-up is ignored. In order to study the heat build-up mechanisms in quasi-static and dynamic loading and their effects on the mechanical response, monotonic tensile and fatigue tests were carried out on both flat and axisymmetric tensile samples with two notch radii, i.e. with various initial stress triaxiality ratios. Sample images were recorded during mechanical loading for re-necking and notch opening measurement after image post-processing, whereas the temperature rise was measured by an Infrared camera. A significant dependence of the temperature field with the notch root radius was observed. Under the same loading condition, samples with smaller notch root radius showed more brittle failure. The elastic compliance, the maximum net stress and failure characteristics were all influenced by the stress triaxiality ratio and crosshead speed. For instance, the higher the crosshead speed, the higher the maximum net stress. A good correlation was obtained between the heat build-up temperature evolution and the region of the re-necking as well as that of the initiation of final failure; moreover, a significant heat build-up was observed during the crack propagation [2]. [1] G.I. Taylor and H. Quinney. The latent energy remaining in a metal after cold working. Proc. R. Soc. Lond. A, 143, 1934. [2] D. Rittel. An investigation of the heat generated during cyclic loading of two glassy polymers. part i : Experimental. Mechanics of Materials, 32(3) :131 – 147, 2000.

Mots clés: Polymers; Thermo-mechanical coupling; Stress heterogeneity; Heat build-up

Domaines: Matériaux; Matériaux et structures en mécanique [physics.class-ph]

Lili Wan, Lucien Laiarinandrasana, C Ovalle. The heat build-up and stress heterogeneity effects on PE. 30ème Colloque national sur la DEformation des Polymères Solides - DEPOS30, Sep 2021, La Napoule, Alpes-Maritimes, France. ⟨hal-03510860⟩