Hickson, RoslynBarry, StevenMercer, Geoffry2015-12-100017-9310http://hdl.handle.net/1885/58680Traditional averaging methods for multilayer diffusion give inaccurate approximations of critical time behaviour, such as the heating time of a material. In particular, they fail to capture the importance of layer order. We use a perturbation expansion of an exact solution to find a simple approximate solution which accurately describes the critical time for transport across multiple layers. This approximate solution is then used to find a correction for the averaging method which captures the key critical time behaviour.Keywords: Approximate solution; Averaging method; Critical time; Exact solution; Heating time; Multilayer diffusions; Multiple layers; Perturbation expansions; Time lag; Composite materials; Diffusion; Laminates; Multilayers Composite materials; Critical time; Diffusion; Laminates; Multilayer; Time lag200910.1016/j.ijheatmasstransfer.2009.08.0122016-02-24