Factors which influence the reliability of the assessment of interfacial bonding in fibrous composites using the pull-out test

Recent developments in the single fibre pull-out technique has made it poss ible to determine the interfacial shear strength tau (i) (IFSS), the toughn ess of the interface G(i) and the matrix shrinkage pressure on the fibre P- o utilizing this test. In contrast, other techniques only allow the determi nation of the IFSS. However, scatter in the values of the IFSS and the othe r interfacial parameters has been reported by different researchers working on a given fibre-matrix composite system using this technique. This brings into question the reliability of results from such analyses. Careful exami nation indicates that such scatter can probably be attributed to factors su ch as the testing configuration and specimen geometry which were previously ignored. The governing equations for analysis of experimental data have be en shown to depend on the loading configuration. It will also be demonstrat ed that different fibre-matrix systems require modified assessment methodol ogy since the range of experimental pull-out data which can be gathered wou ld differ. This is due to the fact that the maximum embedded length specime n which can be pulled-out successfully during testing is dependent on the p hysical properties of the fibre and matrix, and the interfacial bond streng th. Analysis methodology developed based on a recognition of these factors allows reliable assessment of interfacial bonding in fibrous composites. (C ) 2001 Elsevier Science Ltd. All rights reserved.