MORI-TANAKA MEAN-FIELD HOMOGENIZATION BASED FAILURE PREDICTIONS OF A SHORT FIBER COMPOSITE BUTT-JOINT COMPTEST 2015 Bas Tijs 1, Wouter Wilson 2, 3, Steyn Westbeek 3, Max Markestein 1 1 Fokker Aerostructures B.V., Industrieweg 4, 3351 LB, Papendrecht, The Netherlands Fokker Landing Gear B.V., Grasbeemd 28, 5705 DG, Helmond, The Netherlands 3 Eindhoven University of Technology, Den Dolech 2, 5612 AZ, Eindhoven, The Netherlands 2 Content 1. Skin-stringer butt-joint connection 2. Modelling approach 3. Manufacturing & testing of dogbones 4. Detailed butt-joint testing & predictions 5. Conclusion & future work 2 Skin-stringer butt-joint connection Manufacturing concept of butt-joint Thermoplastic pre-forms are co-consolidated to skin lay-up during skin consolidation Skin UD lay-up Web laminate Cap laminate Injection moulded filler 3 Skin-stringer butt-joint connection Anisotropy of Short Fiber Reinforced Plastic filler Anisotropy of Short Fiber Reinforced filler 4 Modelling approach Parametric butt-joint model Parametric Abaqus butt-joint model: LARC04 UVARM implemented to monitor first ply & matrix failure in skin (developed by C.S. Lopes) 5 Parametric: - Loading: 3PB or Peel - Layup - Span - Filler geometry - Filler material (UMAT) Modelling approach Two modelling approaches 1) Approach based on test-data, using default ABAQUS functionality: • Input elastic properties of compound: - E1, E2, nu12 measured - Other elastic properties estimated by M-T method • Input plasticity & damage curve: - Plasticity with Hill’s potential function for anisotropic behaviour - Ductile damage with tabular displacement input • Perform parameter studies on geometry: Filler geometry, skin layup, span, loading 2) M-T ABAQUS User-defined Material routine (UMAT) : • Input: matrix, fiber & geometrical properties • Input: Resin plasticity & damage constants • Perform parameter studies on compound & geometry: Matrix and/or fiber type, Fiber orientation, aspect ratio, volume fraction Filler geometry, skin layup, span, loading 6 Modelling approach Mori-Tanaka Mean-Field Homogenization • Smeared out micro scale information Volume averaging via volume fraction • Based on the Eshelby inclusion problem • Only non-elastic phenomena in the resin – Isotropic damage => logarithmic damage growth until exponential rapid failure – Plasticity => power law hardening rule • Update Eshelby tensor according to new resin Poisson’s ratio 7 Modelling approach Mori-Tanaka Mean-Field Homogenization Fiber : inclusion angle aspect ratio volume fraction (4 fibers, 2 rotation planes for 3D implementation) 8 Modelling approach Mori-Tanaka Mean-Field Homogenization • Predict elastic properties (Matlab model) a = 10 xi = 0.2 • Predict coefficients of thermal expansion 9 Manufacturing & testing of dogbones Manufacturing of dogbones Injection molded dogbones 10 Injection molded plates * ref. Modeling of short fiber reinforced injection moulded Composite, A Kulkarni, NANOSTRUC 2012 Manufacturing & testing of dogbones Static test results for different orientations 0-deg Moderate orientation Low orientation 90-deg (not tested in tension) (remark: as moulded behaviour is different then after co-consolidation) 11 Manufacturing & testing of dogbones Plasticity & Damage The damage can be determined from the change in stiffness Plastic (residual) strain 12 * ref. Modelling the nonlinear shear stress–strain response of glass fibre-reinforced composites Van Paepegem, Composites Science and Technology 66 (2006) Detailed butt-joint testing & predictions 3-Point-Bending versus Peel 13 Detailed butt-joint testing & predictions Failure prediction Drop in load due to filler failure: thermal stress released Residual displacement: skin back in “straight” situation after release of thermal stresses 14 • • • The initial stiffness (1-2) Failure of the filler (2-3) Residual stiffness (3-4) Conclusion & future work Conclusion: • • Two approaches applied for predicting the strength of SFRP butt-joint Mean-field homogenization model developed with planar fiber inclusions – • • • • Easy prediction of: – – – Elastic properties Thermal expansion Plasticity / Failure – As a function of: – – – – Matrix and/or fiber type Fiber orientation Fiber aspect ratio Fiber volume fraction UMAT implementation for elasto-plastic-damage behavior Matlab implementation to predict: Elastic properties, CTE’s Cyclic tests used to distinguish between plasticity and damage Failure mode in filler well captured Future work: • • 15 Parameter studies on geometry & compound Extensive model validation: different compounds, loading, geometry
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