International Journal of Advanced Trends in Computer Science and Engineering, Vol.2 , No.1, Pages : 135-138 (2013) Special Issue of ICACSE 2013 - Held on 7-8 January, 2013 in Lords Institute of Engineering and Technology, Hyderabad 135 ISSN 2278-3091 Delamination of an orthotropic cylindrical shell with helically wound fiber reinforcement when subjected to Axial Compression Afroz Mehar #1 ,P. Ravinder Reddy #2 ,G.K. Mohan Rao #3 ,S.Irfan Sadaq #4 # Assistant Professor, Mechanical Engineering Dept, M.J.C.E.T, Hyderabad, India. 1 afrozmehar786@gmail.com 4 irfan.ajai@gmail.com 2 Prof & Head, Mechanical Engineering Dept, C.B.I.T, Hyderabad, India. 3 Associate Professor, Mechanical Engineering Dept JNTU, Hyderabad, India. Abstract The delamination growth may occur in delaminated cylindrical shells under Axial Buckling. This will lead to failure of structure. This paper deals with the instability analysis of delaminated composite cylindrical shells subject to axial compression, using the finite element method. The effect of contact in the buckling mode has been considered, by employing contact elements between the delaminated layers. The interactive buckling curves response of delaminated cylindrical shells has been obtained. It was also observed that the effects of delamination are more apparent when the composite cylindrical shells are subjected to combined axial compression and bending. Using finite element analysis (Ansys) we have found different mode shapes reacting with respect to the winding angle affecting the properties of the cylindrical shell. Key words: composite, laminated cylindrical shell, delamination growth, energy release rates, contact effect I. INTRODUCTION Composite laminates are widely used in engineering because of their specific excellent properties, such as high strength-to-weight ratio, high stiffness-to-weight ratio, designability, and so forth. But there will be delamination damage in composite laminates during the manufacturing processes, for instance, shocks in assembling procedures. When compared with axial pressure, external pressure does not cause local buckling in delaminated composite laminates, but it can drive in the growth of the delamination. And this will drastically reduce the stiffness and the carrying capacity of the laminated structure, resulting in global buckling and failure of structure at last. It is necessary to determine the stress fields of delamination front in order to analyze the delamination growth of laminated structures. Laminated composite materials are increasingly being used in the aerospace, marine, automobile and other engineering industries. This is due to their high strength-to weight and stiffness-to-weight ratios. However, due to the lack of through-the-thickness reinforcement, structures made from these materials are highly liable to failures caused by delamination. Therefore, within a design process, a structure’s resistance to delamination should be addressed to maximize its durability and damage tolerance. Delaminations in composite cylinders may be due to manufacturing defects, transportation impacts and environmental effects during their service life. The presence of delaminations leads to a reduction in the overall buckling strength of the laminated composite cylindrical shells [3–6]. For the past two decades analytical and numerical analyses have been carried out by many researchers to analyze delaminated composite structures, considering their buckling and post-buckling behaviour [7,8]. Almost all of the papers on delamination buckling deal with beams and flat plates. [6,9–17]. The early work belongs to Chai et al. [9] who characterized the delamination buckling models by the delamination thickness and the number of delaminations through the laminate thickness. Due to its mathematical complexity and modelling, very limited information on the subject of delamination buckling of cylindrical shells and panels is currently available [3–5,18–28]. . This paper deals with the computational modelling of delamination buckling of filament wound composite cylindrical shells subjected to axial compression using Ansys. II. GEOMETRY, MATERIALS AND LOADING CONDITIONS Fig. 1. Cylindrical shell with different loading conditions A typical delaminated circular cylindrical shell with length L=18cm, radius r=7.6, and thickness t=0.152cm is shown in Fig. 1. The axial coordinate is x, the circumferential coordinate is y, and the through-the-thickness coordinate normal to the shell middle surface is z. The circumferential