International Journal for Research in Applied Science & Engineering Technology (IJRASET) ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor: 7.177 Volume 7 Issue XII, Dec 2019- Available at www.ijraset.com © IJRASET: All Rights are Reserved 68 Damage Detection and Severity Assessment of Composite Rotor Blade Materials using Modal Analysis for SHM Rashmi Maharaj 1 , Dr. P. Prasanna 2 1 M .Tech. Student, 2 Assistant Professor, Department of Mechanical Engineering, JNTUH College of Engineering, Hyderabad, INDIA Abstract: Structural damage detection has gained increasing attention from scientific community since unpredicted major hazards mostly human losses have been reported. Vibration based damage identification has gained a lot of importance in recent years with increasing applications of composite structures in many areas of engineering. Since the modal parameters are related to the physical properties of laminates, changes can be detected when damage occurs in these structures. There have been several studies dealing with detection of damage through modal parameters, especially frequencies and mode shapes. However, not many of them deal with laminated composites. The present work involves damage detection by variation of natural frequency and mode shapes of undamaged and damaged laminated composite cantilever beam (representing static composite rotor blade) using numerical modal analysis. Initially FEA results validation (Static and Modal Analysis) is done with the experimental results of literature “Experimental analysis of thin walled composite rotor blade model from structural health monitoring aspect by Pradip D.Haridasa, Dr. Prashant M. Pawarb”, (2017) which focused on the experimental study to obtain natural frequencies at different modes for undamaged and damaged model and their effects on the behavior of a composite rotor blade system. This validated FE modeling is further considered for several damage cases for defining methods to obtain the existence, location and severity of damage. For damage detection (existence of damage), percentage change in natural frequency is considered. For damage location, damage algorithm “curvature mode shape method” is considered. Since deviation in mode shape is insignificant, damage algorithm is used to locate damage. The curvature values are computed from displacement mode shapes obtained from modal analysis. These curvature values are used in the damage algorithm for damage location identification. For damage severity along the model based on damage location, the percentage changes in natural frequencies based on damage locations are compared. This work also involves damage severity assessment based on damage location for different laminated composite materials used in composite wind turbine blades (E-glass/Epoxy, S-glass/Epoxy, Kevlar49/Epoxy, Boron/Epoxy). This is done to obtain the suitable laminated composite material for composite wind turbine blades, which has minimum effect on physical properties due to damage. Keywords: FEA, composite, laminates, vibration, damage I. INTRODUCTION A composite is a structural material that consists of two or more constituents combined at macroscopic level and is not soluble in each other. One constituent is called reinforcing phase (fibers, particles or flakes) and the one in which it is embedded is called matrix (continuous). Examples of composite: Concrete reinforced steel, graphite fibers in epoxy. Advantages of composite: Light in weight, corrosion resistance, flexible, dent resistant, etc. The monitoring and identification of damage in a structure at an early stage is very essential in several engineering applications. Structures are required to work safely during their service life. The common structural defect is the presence of damage in a structure. There is generally loss of local stiffness due to damage which alters the mechanical behavior of the structure. Damages may be due to fatigue under service conditions or initiated in very small size during manufacturing process. Unpredictable occurrence of damage may cause catastrophic failure. Structural damage results in unintentional dynamic response of the structure. Example: Crack in composite wind turbine rotor blade, crack in composite helicopter rotor blade. Therefore, damage detection techniques for Structural Health Monitoring become very important. The experimental methods for damage detection require visibility of the damage and easily accessibility during inspection of the structure. Due to these limitations in the experimental procedures, damage detection is possible only on surface or near structural surface. So, there is a need for damage identification methods which can be used for complex structures for the identification of vibration characteristics changes which are indicative of such damage. Structural damage detection of structural engineering has three main parts i.e. finding the existence, location and severity of damage. It is highly desirable to obtain effective damage detection methods (SHM) for structural failures, to detect, locate and quantify the damage situation at the earliest possible stage. Since the modal parameters (natural frequencies, mode shapes and modal damping) are related to the physical