Impact Response of Unidirectional Carbon Fibre Rod Elements with and without an Impact Protection Layer

Abstract

Rods of unidirectional CFRP offer outstanding performance in terms of strength to weight ratio. Their performance is, however, expected to be limited by their resistance to in-service impact threats, especially with regard to compressive loadings. The work reported here has verified that damage is done to unprotected rods at relatively minor impact levels and that a substantial reduction in compressive strength is experienced after impact. Identical rods have been overwound with high modulus aramid fibre under tension to act as a protective layer and subsequently impacted. These rods are much more resistant to impact than the unprotected rods; the best case studied to date being more than three times as strong after impact as the unprotected rods and more than twice as strong when taking the mass of aramid fibre into account. The longitudinal splitting seen in the impacted, unprotected rods has been completely suppressed by the tensioned overwind. This novel approach to reducing the influence of impact on the post-impact properties of composite rods has been validated by these tests.

Keywords

impact unidirectional rods protective layer compressive strength

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References

1. Cantwell, W. , and Morton, J. , (1991) The impact resistance of composite materials—a review. Composites. 22(5). pp. 347-362.

2. Jones, R. , and Baker, A. , (1985) Compressive strength of impact damaged graphite epoxy laminates. Composite Structures. 3. pp. 403-414.

3. Delforse, D. , and Poursartip, A. , (1977) Energy based approach to impact damage in CFRP laminate composites. Composites A. 28A. pp. 647-655.

4. Levin, K. , (1989) Damage tolerance of carbon fibre reinforced sandwich panels. Proc. 3rd ECCM. March. Bordeaux. Elsevier. London. pp. 509-514.

5. Nilsen, P. , and Potter, K. , (1993) Impact tolerance of sandwich panels with advanced fibre face skins, for marine applications. Proc. 6th ECCM. Bordeaux. Elsevier. London. pp. 257-262.

6. Chamis, C. , Hanson, M. , and Serafini, T. , (1972) Resistance of UD fibre composites. Comp. Mat. Testing and Design. (2nd Conf). ASTM STP 497. pp. 324-349.

7. Wisnom, M.R. , (1999) Suppression of splitting and impact sensitivity of unidirectional carbon fibre using tensioned overwind. Composites Part A. 30A. pp. 661-665.

8. Morse, A. , and Piggott, M. , (1990) Relation between fibre divagation and compressive properties of fibre composites. Proc. 35h Int. SAMPE Symposium. pp. 2236-2244.

9. Clarke, A. , Wisnom, M. , and Potter, K. , (1997) A comparison of the mechanical properties of Graphlite unidirectional carbon rod with conventional prepreg. Plastics, Rubber and Composites, Processing and Applications. 26. no. 10. pp. 447-450.

10.

10. Cook, J. , Howard, A. , Parratt, N. , and Potter, K. , (1982) Creep and static fatigue of aromatic polyamide fibre. Proceedings 3rd RISØ International Symposium on Metallurgy and Materials Science. pp. 193-198.