A first approach to the experimental study of fracture parameters in opening and mixed mode by caustics

Among the experimental methodologies used to determine the fracture parameters, considering the up-and-comingpossibility of the caustics technique, the authors have started a search path to provide a setup and reliable testprocedures for determining the K parameter in mode I and mixed mode. This work shows the set-up used and the firstresults. Firstly, the caustics for KI were obtained using a specific loading system to be used on an optical bench; then,the measurement system was transferred on a material testing machine in order to apply loads of greater magnitude.The results obtained are in agreement with the theoretical estimates in the opening mode and they may be consideredpromising for the analysis of mixed mode, although still substantially different from the values observed in theliterature.