Experimental Investigation of Fastener Pull-out Response in Composite Joints under Static and Dynamic Loading Rates
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Experimental Investigation of Fastener Pull-out Response in Composite Joints under Static and Dynamic Loading Rates Nikolaos Perogamvros 1,2
3
& George Lampeas & Adrian Murphy
1,2
Received: 26 March 2019 / Accepted: 12 August 2019/ # The Author(s) 2019
Abstract A novel device is adopted in order to experimentally investigate the effect of various loading rates on the pull-out response of a fastened composite joint configuration. The joint coupons comprise a composite plate made of the carbon/epoxy AS4/8552 material system and a centrally located titanium lockbolt. Tensile-type (pull) loading was applied to the specimens in a velocity range from quasi-static to 2.1 m/s. Both quasi-static and dynamic tests were conducted using the same specimen geometry and boundary conditions, which conform to international and industrial standards. The experim ental work expands the limited literature and understanding of the mechanical response of composite pull-out joints under the action of dynamic loading. The main experimental observations revealed an increase of 15% regarding maximum load values when loading rate shifts from the static to the impact regime, while the failure patterns derived from static and dynamic tests were similar, although the latter presented a more intense damage zone. Keywords Carbon fibre composites . Impact behaviour . Mechanical testing . Joints . Pull-out (pull-through)
1 Introduction Mechanically fastened joints are widely used in the assembly of high performance and high value composite structural systems, e.g. modern aircrafts, advanced vehicular structures, etc.
* Nikolaos Perogamvros [email protected]
1
School of Mechanical and Aerospace Engineering, Queen’s University Belfast, Belfast BT9 5AH, UK
2
Northern Ireland Advanced Composites and Engineering Centre, Belfast BT3 9DZ, UK
3
Laboratory of Technology and Strength of Materials, Mechanical Engineering and Aeronautics Department, University of Patras, 26500 Rion Patras, Greece
Applied Composite Materials
Such joints have lower structural efficiency when compared to adhesively bonded joints [1]. However, mechanically fastened joints are in general more resistant to long-term environmental degradation, and enable structural disassembly and reassembly for maintenance and repair. As mechanically fastened joints introduce discontinuities in the laminated material and the loading distribution they often are the ‘weakest’ elements of the structural system. Thus, fastened joints are typically critical structural elements and their design is key to structural efficiency and the load carrying capacity of the assembled structure. As a result, joint design significantly influences structural weight, structural integrity and safety throughout the service life of the structure. Beyond the initial static design of these structures, further challenges are imposed when the loading rates diverge from the quasi-static (static) regime and move towards dynamic (impact) events. Dynamic loading cases are also realistic loading-scenarios in th
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