Experimental characterization and numerical modeling of a viscoelastic expandable epoxy foam: Time–temperature transformation and time–temperature equivalence diagrams

Abstract

AbstractAn expandable and Fire, Smoke, and Toxicity (FST) compliant epoxy foam is proposed as an interesting alternative to Nomex® honeycomb cores for the development of Multi‐Functional Structures (MFS). The paper first analyzes the processing conditions using several experimental techniques as differential scanning calorimetry (DSC), rheology, and expansion in a closed volume in order to evaluate the reaction kinetics, the chemorheological behavior, and the expansion kinetics of the material. The experimental data are used to identify several empirical models describing the material processing behavior and finally plotting the isothermal time–temperature transformation (TTT) diagram. A typical curing cycle for the foam is used to describe the evolution of the material parameters during the curing process. The fully cured foam is then characterized using optical and laser microscopy in order to identify its cell size distribution and density. Quasi‐static and dynamic machines are used to evaluate its mechanical and dynamical properties. The time–temperature equivalence is finally used to plot the master's curves of the material, representing the evolution of the material viscoelastic properties as a function of the frequency.