Micro-Mechanics Based Modeling of Joule Heating Induced Damage Propagation in Carbon Composite Laminates

Abstract

Recent experimental studies on electrical conduction behavior of carbon fiber reinforced polymers (CFRP) laminates under various current densities have revealed that even when a composite is subjected to a relatively small current, for example five Ampere current applied to a 2.5cm by 2.5 cm specimen, it results in irreversible change in electric resistance of the CFRP laminates in the through-thickness direction, indicating internal structural damage. The understanding of damage initiation and propagation in CFRP under electric current application is of great significance in design and development of applications that utilize the electric properties of CFRP. In this study, a model is formulated with special attention to address the stochastic nature of composite microstructure and material properties. A localized Joule theory is developed to demonstrate the current concentration effects at multiple levels. A micro-structure based resistor network framework from previous studies has been modified to integrate thermal degradation and failure analysis. The model includes: (i) statistical description of composite microstructure including fiber arrangement and distance between fiber contacts; (ii) description of resin rich layer; and (iii) thermal and dielectric breakdown of the material system. By iteratively assessing damage states based on degradation analysis and updating material properties based on damage severity, the damage propagation of laminated carbon composite materials is established. The model is capable of predicting the electric resistivity in multiple directions, and damage states of composite laminates with arbitrary stacking sequence under variable current applications. The research is intended to raise awareness of internal structural damages induced by localized Joule heating. In addition, the quantitative relation between composite microstructure, internal damage state, and electric resistance established from the numerical model can be utilized for designing damage monitoring systems for CFRP laminates.