Measuring the delamination length in static and fatigue mode I tests using video image processing

In order to measure the delamination length in mode I static and fatigue tests, different systems such as the visual methods, embedded fibre Bragg grating sensors and crack gauges are available. These methods have various disadvantages in terms of reproducibility, measurement range, fatigue sensitivity, and cost. The aim of this work is to describe a technique for measuring the delamination length in mode I tests, based on video image processing. Video image processing allows non-contact continuous crack length monitoring in static tests and for the entire fatigue crack propagation curve. A set of static and fatigue tests carried out with the developed method is included in the present work. The static fracture toughness GIC, the G–N fatigue onset curve and the fracture energy rate versus the crack growth rate da/dN for epoxy glass fibre reinforced composites are reported. Results show that visual image processing is a stable technique for facilitating the post-processing of static and fatigue mode I tests.