The forensic study of single fibre pull-out specimens using ToF-SIMS

The single fibre pull-out (SFPO) test has been used to investigate the interfacial interaction between a glass fibre and a polyester matrix system. However, mechanical data alone cannot explain fully the mechanisms of failure, and time-of-flight secondary-ion mass spectrometry (ToF-SIMS) has been utilised to gain insight into the interfacial chemistry of adhesion. The present work employs ToF-SIMS imaging for the forensic examination of fibre surfaces following a SFPO test. Regions of interest have been selected for retrospective spectral analysis. Principle component analysis (PCA) has been utilised to assist the identification of regions of chemical similarity, enabling better image segmentation and the removal of topographic effects. Results are presented which lead to the description of a failure model based upon these complementary analytical techniques. ToF-SIMS has revealed a difference in the surface chemistry at the fibre tip compared to the bulk of the pulled-out region, which correlates with finite element models in the literature that show higher stress states existing at the embedded fibre tip region.