[Hussain, 3(7): July, 2014] ISSN: 2277-9655 Scientific Journal Impact Factor: 3.449 (ISRA), Impact Factor: 1.852 http: // www.ijesrt.com(C)International Journal of Engineering Sciences & Research Technology [329-334] IJESRT INTERNATIONAL JOURNAL OF ENGINEERING SCIENCES & RESEARCH TECHNOLOGY Vibration Analysis of Laminated Composite Plates with Holes Syed Altaf Hussain 1 , V. Pandurangadu 2 , K. Palani Kumar 3 1 Department of Mechanical engineering, R.G.M College of Engineering and Technology, Nandyal- 518501, India 2 Departments of Mechanical Engineering, JNTUACE-Anantapur, A.P, India. 3 Department of Mechanical Engineering, Sri SaiRam Institute of Technology, Chennai-44, India rgmaltaf1@gmail.com Abstract Fiber reinforced composite materials are widely used in variety of engineering applications due to its superior properties than the conventional materials. In this investigation free vibration analysis of four layered angle-ply symmetric laminated plates with various lamination angles (±0 o to ±90 o )s of laminas with different hole locations were presented. The analyzed laminated plates have been made from composite materials: the reinforcement fibers were Graphite and the matrix material is Epoxy. Composite structures may sometimes provided with holes for the purpose of assembling the components, for passing the cables, for inspection and maintenance etc. The ANSYS13.0 software was used for modeling and analysis of the laminated plates under clamped boundary conditions. The eight noded shell99 was used throughout the analysis. Length to height ratio considered is 40 and 200. The ratio of hole area to the plate area is maintained constant throughout the analysis as 0.05. From the analysis it is inferred that the fundamental frequency of laminated composite plates decreases with increase in L/h ratio. Keywords: Free vibration, laminated composite plate, Finite Element Analysis, Lamination angles. Introduction Laminated composite structures are being increasingly used in aerospace, automotive, marine, and civil areas. This is primarily due to their large values of specific strength and stiffness and the advantage that their properties can be tailored to meet practical requirements. The composite structures may some times be provided with different types of holes for the purpose of assembling the components inside the structure, for passing the cables and control mechanisms, for inspection, maintenance etc. The stresses and deformations of steep gradient are induced around these cutouts. The influence of the thickness parameter is inherent at higher modes of vibration. In this paper the effect of cutouts on vibration response of a laminated composite plates ware investigated. Depreciation of the internal mechanism of composite plates are dependent on their own frequencies, estimating the specific characteristics is also difficult because of the non- isotropy of the materials [1, 2, 3]. Jwalamalini, et al.[4] have investigated the stability of a simply supported square plate with openings under in-plane loading is analyzed using a Finite Element program BUCSAP (Buckling Structural Analysis Program). The openings are considered as square and central for the main study but rectangular and central for comparison with other work. Different magnitudes of tension and compression are assumed as initial pre- stress in the transverse direction before the longitudinal stress is applied. Myung Jo Jhung, et al. [5] have studied the free vibration analysis of circular plate with eccentric hole submerged in fluid studied the natural frequencies and mode shapes of the structures due to the existence of hole. Especially if the hole is located eccentrically the vibration behavior of the structures is expected to deviate significantly from that of a plate with concentric hole. Lee and Lim [6] analyzed free vibration response of simply supported isotropic and orthotropic square plates with a square cutout subjected to an in-plane force using the Rayleigh method. They concluded that the in-plane tensile force increases the natural frequency where as increased compressive force decreases the natural frequency until the state of buckling is reached. Sabir and Davies [7] used finite element method to determine natural frequencies of flat square plates containing an eccentrically located square hole. Paramasivam [8] proposed a method to determine the effect of square openings on the fundamental frequency of square isotropic plates for