Issue 38

G. S. Serovaev et alii, Frattura ed Integrità Strutturale, 38 (2016) 392-398; DOI: 10.3221/IGF-ESIS.38.48 392 Numerical study of the response of dynamic parameters to defects in composite structures Grigorii S. Serovaev, Valery P. Matveenko Perm National Research Polytechnic University, Department of Applied Mathematics and Mechanics, 29 Komsomolsky prospekt, Perm, 614990, Russia serovaev@icmm.ru, mvp@icmm.ru A BSTRACT . The purpose of this work is to study three different models of delamination in composite plate (the free mode model, the constrained model and the contact model) and applicability of this models to the vibrational method of damage detection based on frequency shifts. The results of numerical simulation have shown that the free mode model leads to abrupt changes in natural frequencies due to non-physical condition of mutual penetration of adjacent volumes in the defect zone. The constrained and the contact models yield qualitative agreement in shifts of natural frequencies with a change of the defect size. All models have shown the necessity of analyzing shifts of high frequencies to detect small size delamination. K EYWORDS . Natural frequencies; Vibrational methods of damage detection; Delamination. Citation: Serovaev, G.S., Matveenko, V. P., Numerical study of the response of dynamic parameters to defects in composite structures, Frattura ed Integrità Strutturale, 38 (2016) 392-398. Received: 28.08.2016 Accepted: 15.09.2016 Published: 01.10.2016 Copyright: © 2016 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION he estimation of the mechanical state of a structure during its operation based on detection of internal damages has gained a great importance for such rapidly developing fields of production as mechanical engineering, aerospace industry, etc., whose recent trends are toward an increased use of new types of materials. The most widely spread type of defects in composite constructions is delamination, which leads to a separation of the object in the defect zone into several parts, which begin to respond to loads independently of each other [1] while the stiffness of each part is significantly lower than the stiffness of the whole object. The appearance of delamination may be the cause of the deprivation of bearing capacity of the structure, its breakage and decommissioning which indicates the relevance of the problem of damage detection at an early stage of development. The application of visual methods of damage detection is difficult due to internal location of delamination. It is well known that the appearance of defects in a particular place of the structure influences the local stiffness in this zone, which leads to a shift of natural frequencies. This specific feature of structure response is behind the global vibrational methods of damage detection. These methods use different dynamic parameters (eigenfrequencies, mode shapes, curvatures of mode shapes, etc.) to evaluate the state of the investigated structure [2-5].