Early Diagnostics of Damage and Fracture Zones in Composite Materials Using Brittle Strain Gauges and Acoustic Emission

Abstract

The integrated use of the acoustic emission technique and brittle oxide strain gauges for testing the deformation of damage and fracture zones in samples of polymer composite materials (PCM) at the early phases is considered. For the realization of the proposed technique, integrated parameters were used and software including the cluster analysis and the classification of registered AE pulses was developed, which made it possible to differentiate crack formation signals in the brittle layer of a strain gauge from all the other signals that occur at the early phase of the deformation of PCM samples in the online mode. The use of acoustic emission testing and control video recording for the registration of cracks in a brittle oxide strain gauge with the threshold deformation value of 1000 μm/m provided the precise diagnostics of the forthcoming fracture zone in a sample at the early loading phase under the load level of 10–15% of the limiting one long before the beginning of the active PCM structural degradation phase and made it possible to determine the distribution fields of the highest main deformations in the region of a strain gauge and to perform their quantitative evaluation.