Dynamic Mode II Delamination in Through Thickness Reinforced Composites
Through thickness reinforcement (TTR) technologies have been shown to provide effective delamination resistance for laminated composite materials. The addition of this reinforcement allows for the design of highly damage tolerant composite structures, specifically when subjected to impact events. The aim of this investigation was to understand the delamination resistance of Z-pinned composites when subjected to increasing strain rates.
Z-pinned laminated composites were manufactured and tested using three point end notched flexure (3ENF) specimens subjected to increasing loading rates from quasi-static (~0 m/s) to high velocity impact (5 m/s), using a range of test equipment including drop weight impact tower and a split Hopkinson bar (SHPB).
Using a high speed impact camera and frame by frame pixel tracking of the strain rates, delamination velocities as well as the apparent fracture toughness of the Z-pinned laminates were measured and analysed. Experimental results indicate that there is a transition in the failure morphology of the Z-pinned laminates from quasi-static to high strain rates. The fundamental physical mechanisms that generate this transition are discussed.
KeywordsThrough thickness reinforcement Damage tolerance Delamination testing Z-pins Strain rate Impact
The authors would like to acknowledge Rolls-Royce plc for their support of this research through the Composites University Technology Centre (UTC) at the University of Bristol, UK.
- 1.Yasaee, M., Mohamed, G., Allegri, G., Hallett, SR.: Delamination resistance of through thickness reinforced composites. In: Proceedings of the 16th European Conference on Composite Materials, Seville (2014)Google Scholar
- 2.Partridge, I.K., Yasaee, M., Allegri, G., Lander, J.K.: Damage-tolerant composite structures by Z-pinning. In: Toughening mechanisms in composite materials, pp. 161–189. Elsevier, Burlington (2015). doi:10.1016/B978-1-78242-279-2.00006-8
- 8.Schlueter, A., Parab, N.D., Chen, W.: Loading rate effects on mode I delamination of Z-pinned composite laminates. In: Song, B., Casem, D., Kimberley, J. (eds.) Dynamic Behavior of Materials, Volume 1. Springer, Cham (2014)Google Scholar
- 9.ASTM-D7905-14. Standard test method for determination of the mode II interlaminar fracture toughness of unidirectional fiber-reinforced polymer matrix composites. ASTM Int. (2014)Google Scholar
- 10.ASTM D790-07. Standard test methods for flexural properties of unreinforced and reinforced plastics and electrical insulating materials. ASTM Int. 2007e1 (2007)Google Scholar