Single fibre pull-out test versus short beam shear test: comparing different methods to assess the interfacial shear strength

Mechanical characteristics of fibre-reinforced composites are decisively influenced by the fibre/matrix interactions. This work is focused on the comparison of the single fibre pull-out test and the short beam shear test to assess the main advantages of both methods in terms of resource requirements and reliability. Lyocell fibres are used raw and enzymatic modified in thermoplastic (PLA and PP, both methods) as well as thermoset (PTP and Biresin, only short beam shear test) matrices. The IFSS values of the pull-out test are all in the range from 10.93 ± 3.63 to 14.87 ± 5.22 N/mm². The results of the short beam shear test provide significant differences in apparent ILSS for the analysed fibre/matrix combinations. The results of the single fibre pull-out test show no significant differences in IFSS and have a higher variance, but enable a better estimation of the potential of the examined fibre–matrix combination.