Finite element modelling of bridging micro-mechanics in through-thickness reinforced composite laminates

摘要

Delamination and debonding are the major failure modes in laminated composites, which significantly reduce the performance of a structure under compressive or bending loads. To overcome this problem, new composites with through-thickness reinforcement (TTR) have been used to improve the interlaminar strength and damage tolerance of laminated composites [Freitas G, Fusco T, Campbell T, Harris J, Rosenberg S. Z-fiber™ technology and products for enhancing composite design. In: 83rd Meeting of AGARD SMP, 1996, CP-590; Farley GL, Dickinson LC. Mechanical response of composite materials with through-the-thickness reinforcement. NASA CR-14753, 1993. p. 123-43; Cartie DDR, Partridge IK. Delamination behaviour of Z-pinned laminates In: Williams JG, Pavan A. editors, Proceedings of second ESIS TC4 conference, Les Diablerets, Switzerland, 13-15 September 1999, ESIS Publication, 2000. ISBN 008 043710-9; Greenhalgh E, Hiley M. The assessment of novel materials and processes for the impact tolerant design of stiffened composite aerospace structures. Comp Part A: Appl Sci Manuf 2003;34(2):151-61. [1-4]]. Although the TTR can change the structural elastic response of a composite laminate [Stringer LG, Hiley MJ. Through-thickness reinforcement of composites: Z-pinning, Stitching, and 3D weaving. In: 14th International conference for composite materials, ICCM14, 11-14 July, San Diego, CA, 2003; Mouritz AP, Leong KH, Herszberg I. A review of the effect of stitching on the in-plane mechanical properties of fibre-reinforced polymer composites. Composites Part A 1999;28A:979-91; Grassi M, Zhang X, Meo M. Prediction of stiffness and stresses in z-fibre reinforced composite laminates. Comp Part A: Appl Sci Manuf 2002;33(12): 1653-64; Patridge IK, Cartie DDR, Troulis M, grassi, M, Zhang X. Evaluating the mechanical effectiveness of Z-pinning. In: Proceedings of SAMPE/Dayton technical conference, 2003. [5-8]] they start working only when delamination propagates in their field, which provides non-linear bridging closure forces that shield the delamination crack from the full delaminating force and moment of the applied loads [Grassi M, Zhang X. Finite element analyses of mode I interlaminar delamination in z-fibre reinforced composite laminates. Comp Sci Technol 2003;63(12): 1815-32; 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(3):345-64. [9,10]].