Infrared thermography of carbon fiber reinforced plastics (CFRP) with a hybrid matrix

Abstract

The expansion of the fields of application of polymer composite materials (PCM), the emergence of their new compositions and structures is the reason for the development of new and improvement of existing methods for their non-destructive testing. One of the most important tasks in the performance of non-destructive testing of PCM is the development or selection of control modes. The complexity of solving this problem is related to the anisotropy of PCM properties (thermophysical, acoustical, etc.). The article describes the methods and results of infrared thermography of carbon fiber reinforced plastics with a hybrid matrix formed by an epoxy binder and a silicone elastomer. Silicone elastomer is an independent "liquid" phase in the matrix structure (from the standpoint of relaxation properties). The silicone elastomer has high heat resistance, therefore, the choice of modes for performing active infrared thermography of PCM with a hybrid matrix, in which the "liquid" phase is this material, is a rather complex scientific and practical task. The excess temperatures reported to the control object should be in the range of values at which an informative temperature diagnostic signal is observed, but at the same time the destruction of the PCM components does not occur. The values of temperature diagnostic signals from the location zone of the "liquid" phase in the structure of carbon fiber reinforced plastics are presented. It has been established that in order to perform infrared thermography, the temperature of the diagnostic signal from the location zone of the silicone elastomer must be ~3 ± 0.5°C higher than the temperature of the carbon fiber reinforced plastics. The optimal observation time of the temperature diagnostic signal is the period from the end of heating to 0.5 minutes after heating. A model for determining the modes of infrared thermography based on the phonon theory of heat conduction is presented. The temperature corresponding the appearance of a diagnostic signal from the location zone of the "liquid" phase component of the hybrid matrix of the PCM can be considered the Debye temperature of the test material