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