Fokker Aerostructures Structural Performance of Fiber-Placed, V i bl Stiff C it C i l Variable-Stiffness Composite Conical and Cylindrical Shells Fokker Aerostructures B.V. is a company of the Stork Group Agnes Blom, PhD – Boeing Seattle, January 2011
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Structural Performance of Fiber-Placed, Variable-Stiffness Composite Conical and Cylindrical Shells
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Fokker Aerostructures
Structural Performance of Fiber-Placed,V i bl Stiff C it C i lVariable-Stiffness Composite Conicaland Cylindrical Shells
Fokker Aerostructures B.V. is a company of the Stork Group
Agnes Blom, PhD – Boeing Seattle, January 2011
Fokker Aerostructures B.V. Agnes Blom, PhD - Boeing Seattle, January 2011
IntroductionIntroductionOutline• Introduction
• Variable-Stiffness Laminates
• Design Studies: g
• Axial Stiffness Variation on Conical Shells to Maximize Fundamental Frequencies
• Circumferential Stiffness Variation on a Cylinder to Maximize Load-Carrying Capability in BendingCapability in Bending
• Manufacturing using Advanced Fiber Placement (AFP)
• Experimental Validation:
• Modal Test
• Bending Test
• Conclusions
Structural Performance of Fiber-Placed, Variable-Stiffness Composite Conical and Cylindrical Shells
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Fokker Aerostructures B.V. Agnes Blom, PhD - Boeing Seattle, January 2011
IntroductionIntroductionOverall research objectives
• Weight reduction and structural response improvements of tailored cylindrical and conical shells with fiber-placed laminateslaminates
• Understanding, predicting, and verifying structural g g y gresponse characteristics of variable-stiffness laminates
Structural Performance of Fiber-Placed, Variable-Stiffness Composite Conical and Cylindrical Shells
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Fokker Aerostructures B.V. Agnes Blom, PhD - Boeing Seattle, January 2011
Variation of in plane stiffness is dominant factor
Structural Performance of Fiber-Placed, Variable-Stiffness Composite Conical and Cylindrical Shells
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Variation of in-plane stiffness is dominant factor
Fokker Aerostructures B.V. Agnes Blom, PhD - Boeing Seattle, January 2011
Cylinder Design – Constant ThicknessCylinder Design Constant ThicknessBest steered candidate (BMS8-276)(18% i i b kli l d)(18% increase in buckling load)
• Loads near θ=0˚ and θ=180˚ increase due to higher in-plane stiffness• Buckling load increases because bending stiffness increases more
than load
Structural Performance of Fiber-Placed, Variable-Stiffness Composite Conical and Cylindrical Shells
26Bending stiffnessIn-plane load distribution
Fokker Aerostructures B.V. Agnes Blom, PhD - Boeing Seattle, January 2011
Cylinder DesignCylinder DesignConstant thickness versus overlap• Constant-thickness laminates improve the performance by tailoring the
internal load distribution through in-plane stiffness variation• Overlap laminates improve the performance by increasing the laminate
thickness locally, thereby increasing the bending stiffness → this is opposite the constant-thickness principles
• Overlaps are function of angle variation → in-plane and out-of-plane stiffness are coupled
• Overlap laminates have potential, but more developments are needed to come up with realistic designs (limited amount of overlap, not too oriented, overlap decoupled from fiber angle variation)
• Constant thickness laminates require tow cutting/restarting, but can already be designed realistically
Structural Performance of Fiber-Placed, Variable-Stiffness Composite Conical and Cylindrical Shells
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Fokker Aerostructures B.V. Agnes Blom, PhD - Boeing Seattle, January 2011
ManufacturingManufacturing
Structural Performance of Fiber-Placed, Variable-Stiffness Composite Conical and Cylindrical Shells
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Fokker Aerostructures B.V. Agnes Blom, PhD - Boeing Seattle, January 2011
Structural Performance of Fiber-Placed, Variable-Stiffness Composite Conical and Cylindrical Shells
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Fokker Aerostructures B.V. Agnes Blom, PhD - Boeing Seattle, January 2011
Conclusions (1)Conclusions (1)Variable-stiffness composite design and verification• Developed laminate definitions for variable-stiffness, fiber-placed
conical and cylindrical composite shells• Implemented variable-stiffness definitions in a FEM• 20% improvement in fundamental frequency of conical/cylindrical
shells with axial stiffness variation (analytical)• > 18% improvement in bending load carrying capability of cylindrical
shells with circumferential stiffness variation (analytical + experimental)• Built 3 shells: 2 baselines and variable-stiffness shell• Modal test showed experimental eigenvalues are within 5% of p g 5%
analytical values• Bending test has good correlation with analysis: strains of VS shell