Scientific Research and Essay Vol.4 (9), pp. 914-920, September, 2009 Available online at http://www.academicjournals.org/SRE ISSN 1992-2248 © 2009 Academic Journals Full Length Research paper An experimental investigation into the buckling of GFRP stiffened shells under axial loading Mojtaba Yazdani 1 , Hossein Rahimi 1 , Akbar Afaghi Khatibi 2 and Saeed Hamzeh 3 1 Department of Mechanical Engineering, Tarbiat Modares University, P. O. Box 14115-143 Tehran, Iran. 2 Department of Mechanical Engineering, University of Tehran, P. O. Box 11365-4563 Tehran, Iran. 3 Department of Textile Engineering, Amir Kabir University, P. O .Box 4413-15875 Tehran, Iran Accepted 13 July, 2009 The results of an experimental study on the buckling behavior of thin-walled GFRP cylindrical shells are presented. The specimens were fabricated from continuous glass fiber using a specially-designed filament winding machine. The buckling behaviors of unstiffened shells and stiffened shells with lozenge, triangular and hexagonal grids were then studied under quasi-static axial loading at room temperature. Due to the thin skin of the shells, all specimens first experienced a general buckling mode as well as barreling under the applied loading. Following this general buckling damage, local buckling mode was seen on all specimens. Based on the experimental results, the critical buckling load was higher for the shells with hexagonal and triangular grids while the unstiffened shells and stiffened shells with lozenge grids exhibited much lower critical buckling load. On the other hand, in very small skin thicknesses, when the specific buckling loads for all specimens were compared, the unstiffened shells showed the highest specific buckling load. Key words: Buckling load, composite shells, stiffened shells. INTRODUCTION Structural efficiency is the major concern in today’s aerospace applications. One of the most famous structures in this regard is the grid stiffened composite cylindrical shells. They have certain kinds of stiffening structures either on the inner, outer or both sides of the shell. These types of composite shells have a high buckling capacity together with lower mass comparing to metal shells. Up to now, there is no published research in the literature on the effect of grid parameters on the failure behavior of the stiffened shells with experimental methods. An experimental study was conducted by Baker and Bennett on the buckling of nuclear containment like cylindrical geometries under combined shear and bending [Baker and Bennett, 1984]. They developed a method for determining the static buckling interaction curves of both ring-stiffened and unstiffened cylindrical geometries. Fabrication and testing of thin composite isogrid stiffened shells and panels were described by *Corresponding author. E-mail: [email protected]. Tel.: +982188823007. Fax: +982188838328. Thomas D. Kim [1999, 2000]. In these papers, the fabric- cation and axial compression testing of composite isogrid stiffened shells and panels were discussed. The buckling load of' CFRP unstiffened composite cylinders under combined axial and torsional loadings was investigated by Meyer-Piening. The aim of this study was to determine the buckling load of unstiffened cylindrical shells with different laminate lay-ups. Several shells were tested under axial compression and also under combined axial compression and superimposed torsion. It was found that the stiffness eccentricity of the laminate plays a significant role on the magnitude of the axial buckling load, while this effect is somewhat marginal for combined loads [Meyer-Piening, 2001]. Bisagni conducted an experimental study on the buckling and post-buckling behaviors of four unstiffened thin-walled CFRP cylindrical shells (Bisagni and Cordisco, 2003), where test equipment used was able to apply axial and torsional loadings, separately or in combination. The results identified the effect of laminate orientation and showed that the buckling loads were essentially independent of load sequence and the shells were able to sustain load in the post-buckling field without any damage.
An experimental investigation into the buckling of GFRP stiffened shells under axial loading
May 16, 2023
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