Experimental And Numerical Analysis Of Skin/Stiffener Debonding Under Bending Iker Urresti 6 th International Conference on Composites Testing and Model Identification I. Urresti 1 , A. Barrio 1 , J. Renart 2 and L. Zubillaga 1 1 Department of Mechanical Engineering, Ikerlan [email protected], http://www.ikerlan.es 2 AMADE, Polytechnic School, University of Girona [email protected], http://www.udg.edu/ 24/04/2013
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Experimental And Numerical Analysis Of Skin/Stiffener
Debonding Under Bending
Iker Urresti
6th International Conference on Composites Testing and Model Identification
I. Urresti1, A. Barrio1, J. Renart2 and L. Zubillaga1
• 2.2 FRACTURE MECHANICS MODELS AND VALIDATION (2D, 3D)
• 2.3 EXPERIMENTAL CHARACTERIZATION OF ADHESIVE
• 2.4 NON-SPECIFIC 3 POINT BENDING : MODELS AND VALIDATION
• 2.5 SKIN-STIFFENER DEBONDING UNDER BENDING: MODELS AND VALIDATION
• 3 DISCUSSION OF THE RESULTS
• 4 CONCLUSIONS
• 5 PERSPECTIVES AND APPLICATIONS
26th International Conference on Composites Testing and Model Identification
1. INTRODUCTION
1.1 IK4-IKERLAN
Private not-for-profit Technology Centre
Staff of more than 300 qualified researchers and engineers
IK-Ikerlan is part of “IK-4 Research alliance” and also the key technological R&D actor within “Grupo Mondragon” (7th largest business group in Spain)
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Works for a wide variety of domains: transportation (railway and vertical), automation, industrial, medical, home appliances, wind-turbines, etc.
Main industrial partners:
6th International Conference on Composites Testing and Model Identification
1. INTRODUCTION
1.2 MOTIVATION
More and more structures with adhesive joints are being designed in several industries: aeronautical, automotive, wind turbines...
Adhesive joints offer the potential to reduce weight and cost
Prediction of debonding is of vital importance in order to correctly dimension the joints
• Analytical models difficult to apply for complex loading scenarios
• Cohesive Zone Models (CZM) possibility to predict debonding using FEM
EXPLORATION USING A COMMERCIAL FEM CODE (ANSYS)
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Ch.V. Katsiropoulos, et. al,” Fracture toughnessand shear behavior of composite bonded jointsbased on a novel aerospace adhesive”, Composites Part B: Engineering
Lars Chr. Terndrup Overgaard, “Structural Response Analyses of Vestas V52 Wind Turbine Blade”
6th International Conference on Composites Testing and Model Identification
1. INTRODUCTION
1.3 OBJECTIVE OF THE PRESENT WORK
To develop the FEM models and experimental test capabilities to predict the onset (and growth) of adhesive debonding
• Develop and validate the methodology step by step
• Apply methodology to a structural component (skin-stiffener panel)
To test the capabilities of cohesive element formulations that are already implemented in commercial Finite Element software (Ansys).
Acquire knowledge in order to apply the methodology to industrial problems
56th International Conference on Composites Testing and Model Identification
CORRELATION
2. MULTI-LEVEL APPROACH
2.1 MULTI-LEVEL APPROACH SUMMARY Based on the work developed by Bertolini in [1]
Idea is to build the methodology front bottom to top:
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[1] Julien Bertolini, et al. , “Multi-level experimental and numerical analysis of composite stiffener debonding. Part 1: Non-specific specimen level”, Composite Structures, Volume 90, Issue 4, October 2009, Pages 381-391
FRACTURE MECHANICS 2D MODELS
DCB, ENF, MMB tests
FRACTURE MECHANICS 3D MODELS
DCB, ENF, MMB tests
NON-SPECIFIC COMPONENTS
3 point bending test
STRUCTURAL COMPONENTS
7 point bending
6th International Conference on Composites Testing and Model Identification
2. MULTI-LEVEL APPROACH
2.2 FRACTURE MECHANICS MODELS AND VALIDATION (2D)
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[2] Turon, A.; Camanho, P.P.; Costa, J.; Renart, J. "Accurate simulation of delamination growth under mixed-mode loading using cohesiveelements: Definition of interlaminar strengths and elastic stiffness ." Composite Structures 92 (2010): 1857-1864.[3] G. Alfano and M.A. Crisfield. “Finite Element Interface Models for the Delamination Anaylsis of Laminated Composites: Mechanical and Computational Issues”. International Journal for Numerical Methods in Engineering. Vol. 50. pp. 1701-1736. 2001.
DCB: Mode I opening(Double Cantilever Beam)
ENF: Mode II shear(End Notch Fracture)
MMB: Mixed Mode(Mixed Mode Bending)
6th International Conference on Composites Testing and Model Identification
2D models were developed in Ansys for fracture mechanics test models
Input data, material properties, test conditions from Turon et al. [2]
PLANE182, CONTA171, TARGE169 elements are used in Ansys for the 2D model, 0.5mm element size, implicit time integration
Bilinear Cohesive Zone Model (CZM) implemented in Ansys [3]
Results validated against analytical LEFM and Abaqus model (next slide)
Propagation criteria in Ansys
2. MULTI-LEVEL APPROACH
2.2 FRACTURE MECHANICS MODELS AND VALIDATION (2D) Results validated against analytical crack growth predictions and Abaqus model [4]
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DCB(Double Cantilever Beam)
ENF(End Notch Fracture)
MMB(Mixed Mode Bending)
[4] Sarrado, C.; Turon, A.; Renart, J.; Urresti, I. "Assessment of energy dissipation during mixed-mode delamination growth using cohesive zone models." Composites Part A-Applied Science and Manufacturing (2012): 2128-2136.
6th International Conference on Composites Testing and Model Identification
2. MULTI-LEVEL APPROACH
2.2 FRACTURE MECHANICS MODELS AND VALIDATION (3D) 2D fracture mechanics models were extended to 3D
Solid-Shell elements (SOLSH190) were employed
Results were validated against the 2D model previously validated in [6]
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DCB (3D model)(Double Cantilever Beam)
ENF (3D model)(End Notch Fracture)
MMB (3D model)(Mixed Mode Bending)
6th International Conference on Composites Testing and Model Identification
2. MULTI-LEVEL APPROACH
2.3 EXPERIMENTAL CHARACTERIZATION OF ADHESIVE FM-300 film adhesive GIc measured using a DCB test
configuration.
Unidirectional AS4/8552 Carbon/Epoxy
Test Standards were employed [5,6,7]
Stable crack growth with cohesive failure was obtained in 5 out of 10 specimens.
Using the CBT (Corrected Beam Theory) method (ISO 25217): • GIc = 1169 J/m2
Good agreement with other authors: Bertolini: GIc = 1131 J/m2 ,
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[5] ASTM D5528 - 01(2007)e3 Standard Test Method for Mode I Interlaminar Fracture Toughness of Unidirectional Fiber-ReinforcedPolymer Matrix Composites
[6] ASTM D3433 - 99(2012) Standard Test Method for Fracture Strength in Cleavage of Adhesives in Bonded Metal Joints
[7] ISO 25217:2009, Adhesives -- Determination of the mode 1 adhesive fracture energy of structural adhesive joints using double cantilever beam and tapered double cantilever beam specimens
6th International Conference on Composites Testing and Model Identification
GIIc = 2866 J/m2
2. MULTI-LEVEL APPROACH
2.4 NON-SPECIFIC 3 POINT BENDING : MODELS AND VALIDATION (1/3)
Objective to test cohesive elements in a real component with simplified BC-s and loading. 2 test configurations: flat stiffener and T stiffener (sections of the 7 point bending stiffened panel) Skin and stiffener are AS4/8552 Carbon/Epoxy (Skin layup: (90,45,0,-45,-45,0,45,90)s )