A coupled experimental/numerical approach for the modelling of the local mechanical behaviour of epoxy polymer materials

Effect of Thermo-oxidation on the local mechanical behaviour of epoxy polymer materials for high temperature applications

“…The print relaxes progressively as time increases; it can be proved (not illustrated in Fig. 15 , for more details see Minervino et al, 2014) that almost complete relaxation of the print is achieved after long times.…”

“…5 ). The black zones in the optical microscopy images indicate slope changes induced by thermo-oxidation and related to thermo-oxidative induced resin shrinkage ( Minervino et al, 2013;Minervino et al, 2014;Gigliotti et al, 2016 ). It can be noted that measurement scatter is everywhere small, less than 1% (like virgin samples) in zones not affected by thermal-oxidation, and higher in thermo-oxidized layers, in particular close to the external edges.…”

“…11-15 (similar curves for all several samples not illustrated for brevity) give an exhaustive description of the material behaviour during the indentation phase and after load removal, through print relaxation. This information -together with results presented in a precedent paper, focusing on the virgin resin ( Minervino et al, 2014 ), will be exploited for the development and the identification of an ageing dependent constitutive law.…”

“…The constitutive law is modeled within the framework of Prigogine's fluctuation theory and is based on the thermodynamics of irreversible processes (TIP): it represents an enhanced version of the behaviour model presented by the same authors ( Gigliotti et al, 2011;Minervino et al, 2014 ).…”

“…-Section 2 presents the tested material, specimen preparation and the experimental technique, -Section 3 presents experimental results illustrating the evolution of the polymer mechanical behaviour during isothermal ageing observed by local indentation tests, -Section 4 presents the definition of a dedicated variable for the description of the thermo-oxidation phenomena, -Section 5 presents the ageing dependent polymer constitutive law, integrating the introduced variable as an internal variable for the developed material model, and the fundamental of the numerical/experimental approach, recalling the information given in Minervino et al, 2014 , -Section 6 presents parameters identification for several ageing levels by inverse analysis of the experimental results, -finally, Section 8 collects final remarks and conclusions.…”