Delamination Fracture Toughness Benefits of Inter-Woven Plies in Composite Laminates Produced through Automated Fibre Placement

Authors: Jayden Levy, Garth M. K. Pearce

Abstract:

An automated fibre placement method has been developed to build through-thickness reinforcement into carbon fibre reinforced plastic laminates during their production, with the goal of increasing delamination fracture toughness while circumventing the additional costs and defects imposed by post-layup stitching and z-pinning. Termed ‘inter-weaving’, the method uses custom placement sequences of thermoset prepreg tows to distribute regular fibre link regions in traditionally clean ply interfaces. Inter-weaving’s impact on mode I delamination fracture toughness was evaluated experimentally through double cantilever beam tests (ASTM standard D5528-13) on [±15°]9 laminates made from Park Electrochemical Corp. E-752-LT 1/4” carbon fibre prepreg tape. Unwoven and inter-woven automated fibre placement samples were compared to those of traditional laminates produced from standard uni-directional plies of the same material system. Unwoven automated fibre placement laminates were found to suffer a mostly constant 3.5% decrease in mode I delamination fracture toughness compared to flat uni-directional plies. Inter-weaving caused significant local fracture toughness increases (up to 50%), though these were offset by a matching overall reduction. These positive and negative behaviours of inter-woven laminates were respectively found to be caused by fibre breakage and matrix deformation at inter-weave sites, and the 3D layering of inter-woven ply interfaces providing numerous paths of least resistance for crack propagation.

Keywords: AFP, automated fibre placement, delamination, fracture toughness, inter-weaving.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1474616

References:

[1] R. P. Taylor, Fibre composite aircraft - capability and safety. Australian Transport Safety Bureau, 1 ed., 2008.
[2] Z. Aslan and F. Daricik, “Effects of multiple delaminations on the compressive, tensile, flexural, and buckling behaviour of e-glass/epoxy composites,” Composites Part B: Engineering, vol. 100, pp. 186–196, Sep. 2016.
[3] H. Chai, “The characterization of mode i delamination failure in non-woven, multidirectional laminates,” Composites, vol. 15, pp. 277–290, Oct. 1984.
[4] M. B. M. Rehan, J. Rousseau, S. Fontaine, and X. Gong, “Experimental study of the influence of ply orientation on DCB mode-i delamination behavior by using multidirectional fully isotropic carbon/epoxy laminates,” Composite Structures, vol. 161, pp. 1–7, Feb. 2017.
[5] J.-K. Kim and M.-L. Sham, “Impact and delamination failure of woven-fabric composites,” Composites Science and Technology, vol. 60, pp. 745–761, Apr. 2000.
[6] D. Nicholls and J. Gallagher, “Determination of GIC in angle ply composites using a cantilever beam test method,” Journal of Reinforced Plastics and Composites, vol. 2, pp. 2–17, Jan. 1983.
[7] I. Herszberg, M. K. Bannister, K. H. Leong, and P. J. Falzon, “Research in textile composites at the cooperative research centre for advanced composite structures,” Journal of the Textile Institute, vol. 88, pp. 52–73, Jan. 1997.
[8] A. Mouritz, K. Leong, and I. Herszberg, “A review of the effect of stitching on the in-plane mechanical properties of fibre-reinforced polymer composites,” Composites Part A: Applied Science and Manufacturing, vol. 28, pp. 979–991, Jan. 1997.
[9] K. Dransfield, C. Baillie, and Y.-W. Mai, “Improving the delamination resistance of CFRP by stitching—a review,” Composites Science and Technology, vol. 50, pp. 305–317, Jan. 1994.
[10] G. Stegschuster, K. Pingkarawat, B. Wendland, and A. Mouritz, “Experimental determination of the mode i delamination fracture and fatigue properties of thin 3d woven composites,” Composites Part A: Applied Science and Manufacturing, vol. 84, pp. 308–315, May. 2016.
[11] A. Mouritz, M. Bannister, P. Falzon, and K. Leong, “Review of applications for advanced three-dimensional fibre textile composites,” Composites Part A: Applied Science and Manufacturing, vol. 30, pp. 1445–1461, Dec. 1999.
[12] A. Mouritz and B. Cox, “A mechanistic interpretation of the comparative in-plane mechanical properties of 3d woven, stitched and pinned composites,” Composites Part A: Applied Science and Manufacturing, vol. 41, pp. 709–728, Jun. 2010.
[13] P. Robinson and D. Song, “A modified DCB specimen for mode i testing of multidirectional laminates,” Journal of Composite Materials, vol. 26, pp. 1554–1577, Nov. 1992.
[14] C. C. Poe, H. B. Dexter, and I. S. Raju, “Review of the NASA textile composites research,” Journal of Aircraft, vol. 36, pp. 876–884, Sep. 1999.
[15] J. Levy, “Delamination resistance of inter-woven composite plies produced through automated fibre placement,” tech. rep., UNSW Sydney, Feb. 2017.
[16] Park Electrochemical Corp., “E-752-LT CFRP Prepreg Material Datasheet,” Feb. 2015.
[17] “ASTM D5528-13 Test Method for Mode I Interlaminar Fracture Toughness of Unidirectional Fiber-Reinforced Polymer Matrix Composites,” standard, ASTM International, West Conshohocken, PA, Nov. 2013.