ANSYS
Composites Science and Technology 63 (2003) 1815–1832 www.elsevier.com/locate/compscitech Finite element analyses of mode I interlaminar delamination in z-fibre reinforced composite laminates
Marcello Grassi, Xiang Zhang*
Aerospace Engineering Group, School of Engineering, Cranfield University, Bedford MK43 0AL, UK
Received 7 November 2002; received in revised form 12 March 2003; accepted 18 March 2003
Abstract
This paper presents a detailed numerical study of the mode I interlaminar fracture of carbon/epoxy composite laminates with z-fibre reinforcement. The study was performed using a double cantilever beam configuration. A finite element model was developed using thick-layered shell elements to model the composite laminates and non-linear interface elements to simulate the through thickness reinforcements. An existing micro-mechanical solution was employed to model the material behaviour of the interface element. The numerical analysis showed that z-fibre pinning were effective in bridging delamination when damage had propagated into the z-fibre field; these pins provided crack closure forces that shielded the delamination crack from the full delaminating force and moment due to applied loads. Therefore, the z-fibre technique significantly improves the crack growth resistance and hence arrests or delays delamination extension. The numerical results were validated against experimental data. With reference to structural integrity this technique can be used to design a more damage tolerant structure.
# 2003 Elsevier Ltd. All rights reserved.
Keywords: Z-fibre; B. Fracture; C. Delamination; Fibre bridging; Finite element analysis (FEA)
1. Introduction
Delamination is the most detrimental failure mode in aerospace composite structures. To improve structural damage tolerance, new composites with through-thickness reinforcements (TTR) such as z-fibre pinning (or z-pinning), stitching, and 3D woven fabrics have been developed and they are often referred
Marcello Grassi, Xiang Zhang*
Aerospace Engineering Group, School of Engineering, Cranfield University, Bedford MK43 0AL, UK
Received 7 November 2002; received in revised form 12 March 2003; accepted 18 March 2003
Abstract
This paper presents a detailed numerical study of the mode I interlaminar fracture of carbon/epoxy composite laminates with z-fibre reinforcement. The study was performed using a double cantilever beam configuration. A finite element model was developed using thick-layered shell elements to model the composite laminates and non-linear interface elements to simulate the through thickness reinforcements. An existing micro-mechanical solution was employed to model the material behaviour of the interface element. The numerical analysis showed that z-fibre pinning were effective in bridging delamination when damage had propagated into the z-fibre field; these pins provided crack closure forces that shielded the delamination crack from the full delaminating force and moment due to applied loads. Therefore, the z-fibre technique significantly improves the crack growth resistance and hence arrests or delays delamination extension. The numerical results were validated against experimental data. With reference to structural integrity this technique can be used to design a more damage tolerant structure.
# 2003 Elsevier Ltd. All rights reserved.
Keywords: Z-fibre; B. Fracture; C. Delamination; Fibre bridging; Finite element analysis (FEA)
1. Introduction
Delamination is the most detrimental failure mode in aerospace composite structures. To improve structural damage tolerance, new composites with through-thickness reinforcements (TTR) such as z-fibre pinning (or z-pinning), stitching, and 3D woven fabrics have been developed and they are often referred
References: Panel, 1996. Fracture of Composites (DFC6), Manchester, 2001. Fracture of Composites (DFC5), London, 1999. pp. 60–68. Int. Mechanical Eng. Congress and Expo., 2000. p. 89–99. [29] Crisfield MA. Non-linear finite element analysis of solids and structures, 1997.