Z-pinned laminates

Figure 8. Computer simulation of mode I delamination of z-pinned laminated composites. Solid lines represent the simulation results and dots represent the experimental data [7].

EFFECTS OF MESOSTRUCTURE ON CRACK GROWTH CONTROL CHARACTERISTICS IN Z-PINNED LAMINATES... 

Cartie D.D.R and Partridge I.K., (2000) Delamination behaviour of Z-pinned laminates . Proceedings ESIS Conference on Fracture of Polymers, Composites and Adhesives, ESIS Publication 27, pp. 27-36, Elsevier, Oxford. Proceedings of 2" ESIS TC4 conference, (Les Diablerets, Switzerland, 13-15 September 1999), eds Williams J. G. andPavan A., Elsevier 2000, ISBN 0-08-043710 9. 

Cartie DDR, Brunner AJ, Partridge IK. Effects of mesostructure on crack growth control characteristics in Z-pinned laminates. In Blackman BRK, Pavan A, Williams JG, editors. Fracture of polymers, composites and adhesives II. Elsevier 2003. pp. 503-14. http //dx.doi.org/10.1016/S1566-1369(03)80120-6. 

Bianchi,F. and Zhang, X. (2012) Predicting mode-n delamination suppression in z-pinned laminates. Composires Science and Technology, 72 (8), 924—932. 

The presence of Z-pins as the through-the-thickness reinforcement has been shown to result in dramatic increases in the apparent resistance to crack propagation under Mode I and Mode II loading conditions, in laboratory tests on standard unidirectional (UD) beam samples [2]. The Z-pin pull-out has been identified as the dominant energy micro-mechanism responsible for the resistance to delamination under Mode I conditions. The behaviour of individual Z-pins in pull-out from a UD-laminate has been characterised and modelled and the single Z-pin pull-out curves used as input into a 2D Finite Element (FE) model of delamination under Mode I [3, 4]. 

All specimens were made from IM7/977-2 prepreg supplied by Cytec. One single panel, 300 mm X 750 mm was laid up by hand on a warm table because the prepreg was not particularly tacky. Hot de-bulks (vacuum only, 60 C) were carried out after every fourth layer. A 10 p.m FIFE film was inserted in the mid-plane of the laminate in order to simulate an artificial crack. A final pressurised de-bulk (120 C, 3 bar pressure, 30 minutes) was carried out in order to reach a laminate thickness close to neat cured thickness, prior to Z-pinning with 0.28 mm diameter pins (T600/BMI), at densities of 0.5%, 2% and 4% in the selected locations. Table 1 summarises the range of specimens made. 

Huang H, Waas AM. Compressive response of Z-pinned woven glass fiber textile composite laminates modeling and computations. Compos Sci Technol 2009 69 2338-44. 

Brunner AJ, Terrasi GP, Cartie DDR. Fatigue testing of Z-pin reinforced carbon-fibre laminates. In Proceedings 12th international conference on fracture ICF-12, paper no. 01199 2009. pp. 1-8. 

Mouritz AP. Review of Z-pinned composite laminates. Compos Part A Appl Sci Manuf 2007 38 2383-97. http //dx.doi.Org/10.1016/j.compositesa.2007.08.016. 

Isa MD, Feih S, Mouritz AP. Compression fatigue properties of z-pinned quasi isotropic carbon epoxy laminate with barely visible impact damage. Compos Struct 2011 93 2269-76. 

Fiber reinforced thermosetting polymer composites have been used in the form of laminate, sandwich, grid stiffened, stitched, Z-pinned, three-dimensional (3-D) woven fabric, and hybrid structures. In addition to carrying the designed static/dynamic loads, most composite stmcmres experience some kind of low or high velocity impact incidents during their life cycle. A low velocity impact is not uncommon. For example, dropping a tool on to a composite stmcmre... 

Vaidya, U.K., Kamath, M.V., Hosur, M.V., Mahfiiz, H., and Jeelani, S. (1999) Low-velocity impact response of cross-ply laminated sandwich composites with hollow and foam-filled Z-pin reinforced core. Journal of Composites Technology and Research, 21 (2), 84—97. 

Robinson P, Das S. Mode I DCB testing of composite laminates reinforced with z-direction pins a simple model for the investigation of data reduction strategies. Eng Fract Mech 2004 71 345-64. http //dx.doi.org/10.1016/S0013-7944(03)00116-4. 

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