Abstract
Cocuring process is a unique characteristic of composite materials wherein multiple parts like stringers, ribs and spars are simultaneously cured and bonded to a composite skin resulting in an integral structure. It has many benefits like reduction in part count, elimination of stress concentration due to fastener holes in the cocured regions and reduced assembly time and related costs. However, the application of cocuring has been limited on contoured components because of the complexities associated with the tooling. The basic requirements to be fulfilled are (a) consolidation of skins and stiffeners and (b) dimensional tolerance on position and thickness of stiffeners. Proper consolidation can be ensured through the faithful transfer of autoclave pressure by designing tools which are flexible so that they conform to desired shape whereas the positional tolerance can be achieved by using rigid tools. The resolution of such conflicting requirements requires a detailed study of the geometry of the part, design requirements and tolerances achievable on tools. This paper discusses design of tools for two types of cocured structures viz., open and closed cocured structures. The tooling technologies for realising above structures differ considerably. A few tooling concepts have been discussed based on the authors’ experience of developing cocured structures over the last two decades.
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Acknowledgments
Concepts discussed in the paper have been experimented and fine tuned by scientists/technologists of Advanced Composites Division (ACD) of CSIR-NAL for a period of over two decades. These concepts have been translated to real-life applications on many aircraft programs successfully. Authors would like to acknowledge the inputs received from their esteemed colleagues on various aspects of cocuring. Authors would like to thank Director, NAL and Head, ACD for their unstinting support. Authors would like to show their appreciation to various groups of the Division that are involved in processing and NDE of composites. Authors express their heartfelt thanks to the staff of ACD who directly or indirectly involved in developing cocuring technologies.
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Gaddikeri, K.M., Gowda, M.N.N., Sundaram, R. et al. Innovative tooling concepts for cocured composite structures in aircraft applications. Int J Adv Eng Sci Appl Math 6, 142–147 (2014). https://doi.org/10.1007/s12572-015-0119-0
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DOI: https://doi.org/10.1007/s12572-015-0119-0