European HyperWorks Technology Conference 2011 Series-Production Automotive Hood in Integral CFRP Design Bonn, November 9 th 2011 Dipl.-Ing. Kristian Seidel, Univ.-Prof. Dr.-Ing. Lutz Eckstein Institut für Kraftfahrzeuge RWTH Aachen University Slide Nr. 1
Agenda Introduction Motivation Project Description Requirements Simulation and Design of CFRP Summary Slide Nr. 2
Fibre reinforced plastics in automotive engineering Introduction FRP in Automotive Research at ika Full vehicle competence Functions & requirements Integration & assembly Testing & assessment Vehicle E / E Driver Assistance Body Chassis Drivetrain Acoustics Material Characterisation Simulation Optimisation Verification Production Fibre manufacturing Semi-finished products Polymer processing Handling Slide Nr. 3
Agenda Introduction Motivation Project Description Requirements Simulation and Design of CFRP Summary Slide Nr. 4
Motivation Future Mobility Energy costs will increase further in medium term Fuel consumption and emissions will be strongly financially sanctioned in the future Emissions gain major impact on mobility, e.g. in congested urban areas Harmonising the qualities efficiency, safety and driving experience. EFFICIENCY Vehicle Concepts Architecture & Functions Materials Vehicle DRIVING PLEASURE Driving please despite ADAS SAFETY Slide Nr. 5
103% 31% 88% 144% 365% 57% 5% 15% 14% 35% 60% 23% 41% 61% 96% 44% 9% 17% 19% 30% 105% 32% 91% 152% 436% Motivation Potential of Fibre Reinforced Plastics Stiffness and strength of fibre reinforced plastics (FRP) are strongly depending on the direction (anisotropy) Carbon fibre reinforced plastics (CFRP) have highest specific properties Superior buckling stiffness and dent resistance of FRP e.g. outer panels Particularly for structural parts fibres have to be aligned to the load to achieve considerable weight reduction 100% 80% 60% 40% 20% 0% Steel (500 MPa) CFRP uni-directional GFRP uni-directional Aluminium (400 MPa) CFRP quasi-isotropic CFRP quasi-gsotropic Slide Nr. 6
Costs / unit Potential of FRPs in cars Future vehicle development Rising diversity of derivates Decreasing production volume Higher level of individualisation Economic FRP production current Metal future future EV FRP current FRP future FRP future with EV Production volume 1985: 9 Segments 2008: 40 Segments Price Driving experience Versatility / benefit Prestige Driving experience Price Versatility / benefit Lower fixed costs offer advantages for lower production volumes Exploitation of higher production volumes by reducing variable costs Flexible production by variable manufacturing facilities Flexible and economic production for lower production volumes Prestige [Source: Volkswagen AG] Slide Nr. 7
Agenda Introduction Motivation Project Description Requirements Simulation and Design of CFRP Summary Slide Nr. 8
Hightech.NRW CFRP Body Panels Project goals: Technological and economical potential analysis Simulation of CFRP under static and dynamic loads Load, material and production suited design Enhancement of production concepts (gap impregnation) regarding cycle times and class-a surface quality Funding: Ministerium für Innovation, Wissenschaft und Forschung (MIWF) within funding call Hightech.NRW Duration: 01/2010 12/2012 Partner: Technology demonstrator Slide Nr. 9
Hightech.NRW - CFRP Body Panels Production Production scenario: 10,000 units p.a. Gap impregnation Fast impregnation Low pressure High level of automation Low cycle times Production process chain Material supply Trimming Preform manufacturing Material supply Trimming Preform manufacuring Gap impregnation Gap impregnation Finishing Storage Reduction of production costs Finishing Storage Slide Nr. 10
Agenda Introduction Motivation Project Description Requirements Simulation and Design of CFRP Summary Slide Nr. 11
db [W/m² N] Acceleration [g] Kraft [N] Kraft [N] Hightech.NRW - CFRP Body Panels Benchmark Design benchmark Functional benchmark Global stiffness Torsion stiffness Longitudinal stiffness Lateral stiffness Local stiffness Buckling stiffness Dent resistance Acoustics Noise intensity Sound transition loss Pedestrian protection Euro NCAP head impact Analyse Beulsteifigkeit Motorhaube 10.01.2011 VW Golf VI (MJ 2010) - Messpunkt BS1 300 250 200 150 C i = 77,2 N/mm 100 SOC 50 0 0 2 4 6 8 10 12 14 Torsionssteifigkeit Deformation [mm] 120 100 Ford Focus (MJ 2010)-Außenblech Ford Focus (MJ 2010)-Strukturinnenblech 80 Toyota Auris (MJ 2010)-Außenblech Toyota Auris (MJ 2010)-Strukturinnenblech Toyota Prius (MJ 2010)-Außenblech 60 Toyota Prius (MJ 2010)-Strukturinnenblech Volvo C30 (MJ 2010)-Außenblech 40 Volvo C30 (MJ 2010)-Strukturinnenblech VW Golf VI (MJ 2010)-Außenblech VW Golf VI (MJ 2010)-Strukturinnenblech 20 Ford Focus (MJ2011)-Außenblech Ford Focus (MJ 2011)-Strukturinnenblech 0 0 5 10 15 20 25 30 35 40 45 Auslenkung [mm] 93090SK001 Ford Focus Serienhaube Impaktpunkt 1 Fußgängerschutzversuch Beschleunigung-Zeit-Diagramm HIC_15 = 510,9 v = 39,641 km/h 27.05.2011 140 resultierende Beschleunigung 130 120 110 100 90 80 70 60 50 40 30 20 10 0 0,000 0,005 0,010 0,015 0,020 0,025 0,030 0,035 0,040 0,045 0,050 Time [s] Transferfunktion -12 Focus 2010-10 Auris -8 Prius Volvo C30-6 Golf VI -4 Mittelwert -2 0 100 300 500 700 900 1100 1300 Terz [Hz] Slide Nr. 12
Force [N] Hightech.NRW - CFRP Body Panels Buckling Stiffness & Dent Resistance Buckling Stiffness Elastic buckling (e.g. polishing, oil canning) Circular indentor (d = 50 mm) Force up to 250 N Dent Resistance Plastic deformation (e.g. Hail, stone impact) Spherical indentor (d = 25 mm) Force up to 200 N Solver: RADIOSS 10.0 (explicit) 300 250 200 150 100 50 0 Buckling Stiffness / Dent Resistance 0 Displacement 2 4 6 [mm] 8 10 BS3 Simulation BS5 Simulation BF4 Simulation BF5 Simulation BS3 Test BS5 Test BF4 Test BF5 Test Slide Nr. 13
Hightech.NRW - CFRP Body Panels Pedestrian Protection Euro NCAP Head Impact 40 km/h, 50 Child head (3.5 kg) Head Injury Criteria: ΔHIC 3 % 2,5 t2 1 HIC max a(t)dt (t2 t1) 1000 (t2 t1 ) t 1 Slide Nr. 14
Agenda Introduction Motivation Project Description Requirements Simulation and Design of CFRP Summary Slide Nr. 15
Hightech.NRW - CFRP Body Panels Degrees of Freedom for FRP Design Additional degrees of freedom when designing fibre reinforced plastics Lack of experience and uncertainties require advanced CAE support Intelligent optimisation procedures ensure utilisation of material properties Fibre Material Volume Content Shape Standard Design FRP Design Fibre Orientation Laminate Layup Material Matrix Material Thickness Reduction of development costs Maximised weight saving Reduced part costs Slide Nr. 16
Hightech.NRW - CFRP Body Panels CFRP Optimisation Free-shape / free-size optimisation (OptiStruct 10.0.5) Combined optimisation strategy Topography of inner panel (free-shape) Load adapted laminate layup (free-size) Fibre orientation outer panel (discrete size) Considered load cases: Torsion Longitudinal, lateral bending Buckling stiffness Design concept Design refinement Final design Shape change Shape change Review of node set for free-shape optimisation Interpretation of design concept Consideration of package requirements Generation of final mesh Slide Nr. 17
Hightech.NRW - CFRP Body Panels CFRP Optimisation Free-size / Composite size / shuffling optimisation (OptiStruct 10.0.5) Ply book concept (free-size) Fibre orientation outer panel (discrete size) Final ply book (reduced number of plies) Fibre orientation & thickness inner panel (discrete & composite size) Stacking sequence (composite shuffling) Ply book concept Final ply book Shell thickness 0.5-1.75 mm Ply thickness Interpretation of free-size results Definition of patches Thickness 0.5 mm < t < 1.5 mm 2 full plies 12 local plies Δm ~ 65% Slide Nr. 18
[BASF] Hightech.NRW - CFRP Body Panels Material characterisation Tensile test DIN EN ISO 527 4 (non-unidirectional) Tensile test DIN EN ISO 527 5 (unidirectional) Compression test DIN EN ISO 14126 (non- / unidirectional) Tensile shear test DIN EN ISO 14129 (in plane shear) Shear test DIN EN ISO 14130 (interlaminar shear) Dynamic tensile and shear tests Tension / shear L f = 150 mm (0 / 90 / +45 ) Compression L f = 10 mm (0 / 90 ) Shear (interlaminar) 10x20 mm (0 / 90 ) Tension / shear (dynamic) L f = 75 mm (0 / 90 / +45 ) Slide Nr. 19
Hightech.NRW - CFRP Body Panels CRASURV Model CRASURV material model (RADIOSS /MAT/COMPSH) Anisotropic, visco-elasto-plastic, strain rate dependant material behaviour Damage and failure in tension, compression and shear based on plastic work Advanced Tsai-Wu failure model Initial Tsai-Wu is shifted to account for hardening and softening 2: Tsai-Wu after hardening and softening in some directions 1: Tsai-Wu after hardening σ 2 σ σ max maximum stress 0: Initial Tsai-Wu σ 1 σ res W plastic residual stress W elastic elasticity W p1 W p2 W p plasticity 3: Residual Tsai-Wu failure [Altair] erosion [Altair] Slide Nr. 20
Spannung [Mpa] stress [MPa] Spannung [Mpa] stress [MPa] Spannung [Mpa] stress [MPa] Hightech.NRW - CFRP Body Panels Material modelling of CFRP Layered Shell Method (RADIOSS /SH_SANDW or /SH_COMP) Laminate layers are represented as integration points within one shell element Good trade-off between calculation time and accuracy for crash simulation Z Shell element on mid-surface Composite panel: 2 layers FEM Model: 5 layers X, Y 1-2 integration points per layer (material and orientation) [Altair] CRASURV material model (RADIOSS /MAT/COMPSH) Comparison of test and simulation 800 600 400 200 tension Zugversuch 0 0,0 0,5 1,0 1,5 strain [%] Dehnung [%] simulation Simulation test Versuch compression Druckversuch 800 simulation Simulation 600 test Versuch 400 200 0 0,0 0,5 1,0 1,5 2,0 2,5 strain [%] Dehnung [%] 140 120 100 80 60 40 20 0 shear Schubversuch 0 5 10 15 20 25 30 35 strain [%] Dehnung [%] simulation Simulation test Versuch Slide Nr. 21
Kraft [kn] Force [kn] Hightech.NRW - CFRP Body Panels Drop tower test Monolithic CFRP plate (1x400x400 mm) Hemispherical impactor (Ø 114 mm) Impactor velocity up to 30 km/h Impactor mass: 9 kg Solver: RADIOSS 11.0 (explicit) 3,0 2,0 1,0 0,0 Drop CFK CFRP monolithisch tower Monolithic test CFRP 11 mm mm FK002 Simulation 0 Displacement 50 [mm] 100 Weg [mm] Slide Nr. 22
acceleration [g], displacement [mm] HIC [ ] Hightech.NRW - CFRP Body Panels Pedestrian Protection with CFRP Deceleration of the head is determined by a combination of mass inertia and stiffness/strength of the hood Short pulse induced by mass inertia results in a short HIC window and low HIC values for steel hood Missing pulse due to mass reduction (e.g. CFRP) has to be compensated by stiffness/strength which results in a wider HIC window Acceleration is distributed over a longer time period which results in higher intrusions 150 100 Inertia dominated 1.500 1.000 50 500 0 0 0 10 time [ms] 20 30 Steel - acceleration CFRP - acceleration Steel - displacement CFRP - displacement Steel - HIC CFRP - HIC Slide Nr. 23
Agenda Introduction Motivation Project Description Requirements Simulation and Design of CFRP Summary Slide Nr. 24
Weight [kg] Hightech.NRW - CFRP Body Panels Summary -65 %? 40-100% 35 40% % 50% % Pedestrian protection Manufacturing Paint process... Reference Hood CFRP Hood (stiffness) CFRP Hood Increased need for lightweight design and improved production processes offer potential for CFRP applications also for higher volumes Potential of CFRP can only be utilised with load adapted fibre orientation Additional degrees of freedom in FRP design require advanced CAE support (Appropriate simulation models, optimisation tools, ) Expected lightweight potential for CFRP hood of -50 to -60 % Hightech.NRW technology demonstrator at the end of 2012 Slide Nr. 25
Thank you for your attention! Slide Nr. 26
Contact Dipl.-Ing. Kristian Seidel Institut für Kraftfahrzeuge RWTH Aachen University Steinbachstraße 7 52074 Aachen Germany Phone Fax Email Internet +49 241 80 25641 +49 241 80 22147 seidel@ika.rwth-aachen.de www.ika.rwth-aachen.de Slide Nr. 27