Heat transfer and thermal stress analysis in electrified CFRP composites

Abstract

Our recent studies 1,2 demonstrate that application of an electric current to carbon fiber reinforced polymer (CFRP) matrix composites may lead to an increase in the maximum impact load and reduction of the impact damage, whereas a prolonged application of the current has a rather detrimental effect due to current induced heating. In this paper we discuss thermal effects in electrified composites due to applied electric current. In particular, electric induced heating and thermoelastic deformation of electrified carbon fiber polymer matrix composite plates are investigated. I. Composites with coupled electrical, thermal, and mechanical response Carbon fiber polymer matrix composites that constitute the focus of this work consist of electrically conductive fibers and dielectric polymer matrix, and are electrically anisotropic and conductive at the macroscale. Their mechanical behavior in the presence of an electromagnetic field is characterized by a complex array of factors, among which are coupling of the mechanical and electromagnetic fields when both mechanical and electromagnetic loads are applied; Joule heating produced in conductive phases and its effects; changes in the failure mechanisms induced by the electromagnetic field. Some of these factors are either uniquely attributed to the carbon fiber polymer matrix composites, or have distinct characteristics in the composites. For instance, it is well known that the properties of polymer matrix composites are adversely affected by the heating. At temperatures above glass transition, a rapid degradation of the matrix occurs, which leads to deterioration in composite strength and elastic moduli. Thus, thermal effects cannot be ignored in evaluation of the mechanical behavior of composites subjected to even moderate electromagnetic fields and the corresponding problems need to be formulated considering interaction of mechanical, electromagnetic, and thermal fields. Mathematically speaking, in the most general case the problem of electro-thermo-mechanical coupling reduces to solving of equations of motion, Maxwell’s electrodynamic equations, and heat transfer equations. Here we discuss briefly the field equations for mechanically and electrically anisotropic composites subject to the mechanical and electromagnetic loads, which will provide theoretical background for the experimental studies and analysis presented in the following sections. Some of the details of the current discussion and derivations may be found in 3 . Equations of motion for conductive solids in the presence of an electromagnetic field have the form