Acoustic emission of debonding between fibre and matrix to evaluate local adhesion

The paper applies a recently developed test method to discover weak adhesion areas between a fibre and polymer matrix. The basis of the test is the use of a necked sample with an embedded single fibre under tension. An optimised sample geometry guarantees high enough normal tensile stresses at the interface that cause debonding with subsequent fibre fracture and friction. Optimised geometric dimensions and the corresponding transverse stresses are given. While for transparent polymers the moment of debonding can be observed by optical means, the acoustic emission method is practicable also for opaque polymers. The experimentally measured instantaneous load corresponding to an acoustic debonding event is used as input to a combined analytical/numerical data reduction scheme. It calculates the maximum radial stress at the interface corresponding to the instantaneous load.