Spring-In Simulation in Fiber- Composite Manufacturing

Transcription

1 Spring-In Simulation in Fiber- Composite Manufacturing T. Spröwitz, T. Wille, M. Kleineberg, J. Tessmer ECCM June 2008, Stockholm, Sweden Institute of Composite Structures and Adaptive Systems

2 Contents Motivation Material Parameter Identification Analysis of curved Profile Conclusions Institute of Composite Structures and Adaptive Systems 2

3 Motivation High production rate ( 30AC / month) Extreme competition on world market (low earnings / AC) Part production costs and component assembly costs Minimize rejection rate (max. reproducibility) Minimize cycle times (optimal usage of technical equipment) Low-shim assembly Allowable Stresses σ Ω Quelle: Seatle Times Quelle: AIRBUS Manufacturing Fitting Position Test / In-Service Time Institute of Composite Structures and Adaptive Systems 3

4 Motivation General Approach a d tnominal Δθspring-in trt tnominal trt d a Δθ = laminate thickness = laminate thickness after curing = thickness shrinkage = laminate movement = spring-in l outer: length outer fibre (assumed to be constant) Determination of shrinkage parameters using FEM (Nastran) and test results linner: length inner fibre (assumed to be constant) Fibre dominated In Plane Properties Matrix dominated Out of Plane Properties Experimental determination of Springin on L-profile under different process cycles Determination of Spring-In on generic aircraft frame structure Institute of Composite Structures and Adaptive Systems 4

5 Step 1: Experimental Determination of Spring-In Invar RTM mould with integrated thermocouples Reproducable manufacturing using heatable press T V1, Normal T V2, Tgel 180 T V3, Tgel 130 T V7, Tgel 110 Measurement of spring-in angle Variation of process parameters (variation of gel point) Fiber: Matrix: Laminate: HTS RTM6 [4*(±45)] s Institute of Composite Structures and Adaptive Systems 5

6 Step 2: Material Parameter Identification Iso-static mounting 3d Layerwize modeling with solid elements [HEX8] (3 elements per single ply) 2d Fitting position Determination of modified CTE of a unidirectional single ply 1. α F =const, α M adjusted α M = α MT + α MC 2. Calculation of homogenized properties of unidirectional single ply using ESAComp Linear-static FEM simulation of L-profile with modified CTE of unidirectional single plies 4. Matching with experimentally determined Spring-In angles by variation of α MC 5. Validation analyses for different fiber-volume-fractions Institute of Composite Structures and Adaptive Systems 6

7 Step 2: Material Parameter Identification 1. Variation of fiber-cte α F11 from literature survey leads to negligible changes of the Spring-In angle T V1, Normal T V2, Tgel 180 T V3, Tgel 130 T V7, Tgel Matching with experimental results for minimal Spring-In 3. Matrix CTE α MT through parameter variation (assumption: thermal part only) α F11 α M Disp. [mm] Disp. at x 1 [mm] Disp. at x 2 [mm] Δx [mm] β [deg] Institute of Composite Structures and Adaptive Systems 7

8 Step 2: Material Parameter Identification Good correlation between experimental results and analysis for the different fiber-volume-fractions Analytical results lead to lower Spring-In angles Δθ = θ ( α α ) T 1+ α R ΔT ΔT R Institute of Composite Structures and Adaptive Systems 8

9 Step 2: Material Parameter Identification Displacements in iso-static mounting Stresses under iso-static mounting Stresses in fitted position Max. Pressure: Max. Tension: -68 N/mm² +68 N/mm² Max. Pressure: Max. Tension: -158 N/mm² +70 N/mm² Institute of Composite Structures and Adaptive Systems 9

10 Step 3: Profile Analysis Integral Z-Profiles Profiles that have been investigated 2D / 3D Hybrid Models Integral Z-Profiles Integral LCF-Profiles UD Reinforced Inner and Middle Chord Institute of Composite Structures and Adaptive Systems 10

11 Step 3: Profile Analysis Boundary Conditions Iso-static mounting on free edge Global Spring-In angle Residual stress analysis Mounted in fitting position Stress analysis Institute of Composite Structures and Adaptive Systems 11

12 Step 3: Profile Analysis Simulation Results Integral Z-Profiles Global Spring-In Effect: Global Radius Decreases Integral Z-Profiles UD Global Spring-In Effect: Global Radius Increases Integral LCF-Profiles UD UD Global Spring-In Effect: Global Radius Decreases Institute of Composite Structures and Adaptive Systems 12

13 Step 3: Z-Profile Analysis Displacements and Stresses Nominal frame radius Measured radius r nom = mm r mes = mm Process P1 P2 P3 P4 Global Radius Good agreement with measured global radius Stresses: Process Fiber Stresses Chords [Mpa] Fiber Stresses Frame [Mpa] Matrix Stresses [MPa] P P No significant changes of stresses in fitting position Institute of Composite Structures and Adaptive Systems 13

14 Conclusions Spring-In deformation is highly dependent on gel-temperature and fibre-volume-fraction Reproducible process conditions required for cost effective, high precision manufacturing Simple L-shaped coupons can be used to investigate the Spring-In behaviour of complex composite structures Realisation of Spring-In compensated manufacturing moulds possible Lower gel-temperatures lead to reduced Spring-In angles but also increase cycle times significantly Reduced Spring-In angles indicate a lower stress level in the laminate Institute of Composite Structures and Adaptive Systems 14

15 Thank you for your attention! Contact: Tom Sproewitz DLR German Aerospace Center Institute of Composite Structures and Adaptive Systems Lilienthalplatz 7 D BRAUNSCHWEIG tom.sproewitz@dlr.de Phone: Institute of Composite Structures and Adaptive Systems 15