Comprehensive analysis of mechanical behavior and fracture processes of specimens of three-dimensional reinforced carbon fiber in tensile tests

The aim of the work is to develop a procedure of an experimental study related to the inelastic behavior and failure process of a 3D reinforced composite material taking into account the influence of interweaving schemes based on a combined use of optical methods analyzing strain and temperature fields, as well as a method for recording acoustic emission signals. Uniaxial tension tests were conducted for six groups of specimens which preforms were made with the 3D weaving technology in six different ways of weaving. It is noted that the CFRP-samples with the orthogonal and orthogonal conjoint weave scheme are characterized by high values of maximum load compared to the samples with the interlayer reinforcement and layered samples. The choice of the optimal parameters (subset and step) of the correlation processing of digital images in the study of the PEP samples is illustrated taking into account the structural features of the material. We carried out the analysis of changes in the cumulative energy of AE-signals obtained by summing the values of the energy parameter and reflecting the intensity of the accumulation of defects in the material during loading. It was found that the samples with the orthogonal, orthogonal-combined weave scheme, as well as with pairwise interlayer reinforcement, are characterized by a low damage accumulation rate in the material, the process of defect initiation and propagation proceed uniformly. The samples with the pairwise interlayer combined reinforcement with through interlayer reinforcement and layered samples are characterized by the intensity of the crack formation in the material during loading. The results of the analysis and quantitative comparison of parameters (maximum load, ultimate elongation of samples, intensity of local heating of the material at the time of macrodestruction, the maximum value of the cumulative energy achieved at the time of failure, the number of recorded emissions of the AE signal) were obtained for groups of the samples with different weave patterns. It is shown that the multiparameter analysis of the experimental data allows selection of a composite optimal properties during its development in accordance with the required operating conditions.