Mechanics of Fibre Debonding in Structural Battery Composites

The concept of providing power in the form of structural energy storage devices, for example structural supercapacitors and structural batteries, are a potentially viable strategy to achieve both high energy density and a load bearing structure. Structural battery composites, a subclass of composite materials, can provide mechanical integrity and energy storage capability simultaneously. A candidate architecture of a structural battery composite are carbon fibres embedded in an electrolyte matrix material. Mechanical failure mechanisms in structural battery composites are not yet well understood, especially when external mechanical loads are applied. We present modelling results for fibre debonding, a key failure mechanism in a structural battery composite made from carbon fibres and polyethylene oxide (PEO) matrix. We derive the energy release rate for fibre debonding under both electrochemical and mechanical loadings using the solution to the Eshelby's inclusion problem. We discuss the coupling effects of Li content in carbon fibres and external mechanical loads on fibre debonding and provide guidelines for reliable operation of the composite structure.