Composite structure failure analysis post Lithium-Ion battery fire

• A mature modeling framework predicts thermal runaway damage in a FE model. • Heat flux loading representative of cell behaviour is developed. • Single cell runaway damage can potentially reduce the strength of the specimen by 20% • Multi cell runaway damage can potentially reduce the strength of the specimen by 56% The use of composite materials has expanded significantly in a variety of sectors. In road transport, lithium-ion batteries (LIB) are the most commonly used. It is standard practice for batteries to be housed within a metal enclosure, which protects and enables extinguishment in the event of Thermal Runaway (TR). Composite materials have been shown to contribute to lightweighting in many vehicle structures and their use in battery enclosures has been growing in recent years - with the aim of reducing the weight of the battery assembly and positively impacting vehicle range. This work develops Finite Element (FE) models to assess thermal and mechanical damage and failure mechanisms during a TR event considering a section of a composite battery enclosure. Experimental data for a cylindrical 18650 lithium-ion battery fire is studied and used to define representative thermal loading. This validated loading profile is applied to a composite specimen and material temperature data is used to appraise damage. Finally, the predicted damage is used to predict and quantify the residual failure mechanism and strength of the specimen post battery fire. Results have shown the presence of damage from a single cell runaway can potentially reduce the strength of the specimen by 20% while multi-cell runaway can potentially reduce the strength by 56%. The predictive simulation capability herein could be used as a design tool for battery fire protection of composite enclosures, potentially reducing the need for corrective action, minimising the number of physical tests to support design and certification, as well as aiding in the interpretation of physical test results.