EXPERIMENTAL FINDING OF FRACTURE TOUGHNESS CHARACTERISTICS AND THEORETICAL MODELING OF CRACK PROPAGATION PROCESSES IN CARBON FIBER SAMPLES UNDER CONDITIONS OF ADDITIVE PRODUCTION

Abstract

The relevance of the problem stated in this article is that the development of aerospace technology increased the demand for good quality materials. An important issue is ensuring durability in conditions of longterm loads and in conditions of damage development. One of the criteria that ensure the toughness of the material is crack resistance. The aim of the work is to study the interlayer crack resistance (fracture toughness) under loading under conditions of separation and transverse shear, interlayer strength, as well as the effect of temperature on interlayer strength, mechanical tensile properties. A comparison of the values of interlayer crack resistance GIС (separation) and GIIС (shear) and of mechanical tensile properties and interlayer strength of carbon fiber samples is made. The main methods for studying this problem were the short-beam method, the DCB method, the ENF method. The results of the experimental data were compared with modeling the processes of the appearance and development of cracks in the finite element complexes ABAQUS and Ansys based on the VVCT models, cohesive elements. Deviations from the experiment were found and conclusions were drawn that the point of application of the load had to be shifted from the edge of the sample, which will reduce the initial separation and increase the stiffness of the sample. Due to the fact that the cohesion zone model is very sensitive to input parameters, it is necessary to know many parameters and take into account a large number of factors. The practical importance of this work is to show how to use the VCCT model to obtain the critical load of the germination of the first crack. The research technique can be used for further experiments, including simulation further stratification with low inaccuracy.