An experimental method for determining the crack resistance of composite materials based on a comparison of the results of applying the digital image correlation method and the analysis of deformation diagrams has been developed and tested. To determine local load drops (the “pop-in” effect) that occur during the formation of splitting cracks in fiber composites, the window function technique was used. The use of this technique made it possible to clarify the moment of occurrence of the “pop-in” effect and determine the load level used to calculate the critical value of the stress intensity factor at the top of the transverse notch on the composite specimen. Verification of the results obtained from processing the experimental diagrams was carried out by interpolating the distribution of normalized strains recorded at the notch apex using the digital image correlation method. The proposed method of processing experimental data made it possible to obtain correct results of the critical stress intensity factor during bending of composite beams with a transverse notch.
Matvienko et al. (Fri,) studied this question.