Design for Manufacturing Accurate Skin Panels from
Fibre Metal LaminatesBackgroundFibre metal laminates (FMLs) as a new hybrid aerospace material has found applications in structural parts of aircraft like fuselage panels. Different manufacturing processes like cure, adding doublers and splices, cut-outs and post-cure produces residual stresses and shape deviations. To have high performance and accurate skin panels made of FMLs and finally make massive production of FMLs possible without manual action and corrections, it is needed to have models that describe the manufacturing-induced phenomena and predict the final mechanical and geometric state of the structure. In this regard, no considerable research is done on FMLs. The most relevant works available are on some common processes on full composites.If we can model these processes and predict the stresses and distortions, we can reduce them by designing revised layup tools.
Experimental Strategy
Approach 1: Direct/indirect measurement of residual strains of cured samplesMeasurement of:
Curvature Calculation Residual Strain & StressResidual strainsCalculation Residual Stress Ply removal Measuring TStress-Free
Approach 2: Monitoring/measurement during cure Cure-monitoring of:
Curvature Interrupted cureCalculation of Residual Strain & Stress
Residual strainsCalculation Residual Stress Embedded strain gages or fibre optic sensors
Research Methodology
Phase 1: Introduction and Literature Review
Phase 2: Understanding and Measurement of Residual strains (Distortion) in Simple Configurations
Phase 3: Complete Cure Modeling and Measurement of Residual Strains (Distortion) During Manufacture of an FML
Phase 4: Residual Stress (Distortion) in FML Skin Panels, Including Splices, Doublers and Ply-Drop-Off
Phase 5: Experimental Study and Modeling of Residual Stress-Distortion in post-cure Processes of FML Skin Panels
Phase 6: Combining Previous Phases to Achieve a Predictive Model for the Whole Process
Manufacturing Processes Generate Distortion
Manufacturing Processes and effects onResidual Stress (Distortion) of FMLs
PhD Candidate: Morteza AbouhamzehDepartment: ASMSection: Structural Integrity & CompositesSupervisor: J. SinkePromoter: R. BenedictusStart date: 10-02-2012Funding: Cooperations:
Aero
spac
e En
gine
erin
g Preparation
Including:• Cutting sheets
and layers• Forming-layup
Main Cure Cycle- Cure-Cooldown(Chemical & Thermal Parts)- Splices/Doublers
• Important Factors:• Thickness
• Anti-symmetry• Cure cycle (P,T,t)• Resin material
• Fibre volume gradient
Remove from Layup Tool
(Tool-Part Interaction)
• Important Factors:• Thickness
• Surface roughness• Layup tool material
2nd Cure Cycle
Including:Attachment of stiffeners,
doublers and stringers
Trimming & Cut-out
Final Integrated
Panel
Manufacturing FMLs for Fuselage
Model Development
Model 1 (Phase 2):
Linear Elastic (small-displacement)
Model 2 (Phase 2):
Nonlinear Elastic (Large Displacement)
Model 3 (Phase 3):
Linear / Nonlinear Elastic
With cure-dependent material
properties
Model 4 (Phase 4,5):
Nonlinear Inelastic (Plastic)
For Splices and Doublers
With cure-dependent material
properties
Model 5 (optional):
Nonlinear ViscoElastic/Plastic
With cure-dependent material
properties
Current Stage:
Modeling: Cure (cool-down process):Linear elastic modeling (sym./unsym. GLARE panels)Nonlinear (large-displacement) elastic
Experiments:Manufacturing some simple laminates and measuring curvature and strainsDetermination of stress-free temperature (using curved unsym. panles)Determining curvature and residual strains by eliminating one ply from a symmetric FML