Exploring the role of fibre sizing to the fatigue of glass fibre composites using a novel, reliable micro-fatigue test

Single fibre micro-composite tests are among the most reliable methods for characterising the fibre–matrix interphase. To improve their versatility, this study utilises a well-characterised microbond setup in a cyclic loading case to create a so-called micro-fatigue test. The surface of the fibres is controlled to create two distinctive interphase types: a clean glass fibre surface, and a model sizing. The sizing improved the average interfacial performance in all tested cases, but the role of the sizing was most prominent in the fatigue lifetime of the microdroplet samples. Finite element analysis was used to evaluate the strain-rate dependency and heating related to the plastic deformation of the microdroplet samples in cyclic loading and predicted a well behaving experimental setup. The method offers a promising pathway for further studies on interfacial fatigue and the role of sizing in it.