Non-conventional laminates: expanding the design envelope of composite aeronautical structures

1. Non-conventional laminates: expanding the design envelope of composite aeronautical structures Pedro Ponces Camanho, pcamanho@fe.up.pt Departamento de Engenharia Mecânica Faculdade de Engenharia

2. Contents • Introduction. • Computational for models advanced composite laminates. • Non-conventional laminates: • Variable-stiffness panels. • Hybrid laminates. • Conclusions.

3. Introduction 0 90 +45 -45

4. Analysis Reduced Testing } reduced non-recurring costs • reduced reliance on testing • faster design process reduced recurring costs/new concepts for composite materials/structures • more accurate design tools Introduction Structural Levels of Testing & Analysis Building Block Integration. Certification Methodology (Mil-Hbk.-17) Full Scale Article Static/ Fatigue Verification of Design Data and Methodology Components Chronological Sequence Specimen Complexity Sub-components Development of Design Data Structural Elements Design Allowables Coupons Material Selection and Qualifications Coupons Number of Specimens • High-fidelity computational models:

5. Introduction • Objectives: • Reduction of the production costs of aeronautical structures using advanced composite materials. • Reduction of the development & certification costs of aeronautical structures using virtual testing based on computational models. • Reduction of fuel consumption and of CO2 emissions using new highly optimized, lightweigh structures.

6. Computational models for advanced composites

7. Computational models for advanced composites AA587

8. e11 Load Detail of lug area e22 Load 0° Tension Compression g12 2 1 Load Load Failure mode: cleavage Computational models for advanced composites Fabrication, Load CG Dávila, PP Camanho, A TuronJournal of Aircraft, 2008

9. Computational models for advanced composites • Main results • Implementation of the analytical and computational models in commercial software used by the aeronautical industry for the design of composite structures (Abaqus, LS-DYNA, ESACOMP, Hypersizer). • Computational models used in the investigation of the collapse of an aircraft composite structure. • NASA H.J.E. Reid Award for Outstanding Scientific Paper. Collaboration/funding:

10. Non-conventional laminates Airframe structure breakdown by failure mode designing the structure Miscel. 9% Crippling 21% Damage Tolerance 40% Panel Buckling 17% Bearing 13% • Non-Conventional Laminates (NCL): • Laminates with fibre orientations other than the ‘traditional’ 0o, 90o and ±45o. • Laminates with steered fibres – Variable-Stiffness Panels (VSP). • Hybrid laminates. Damage tolerance Panel buckling Bearing

11. Non-conventional laminates

12. Non-conventional laminates

13. Non-conventional laminates

14. Non-conventional laminates Vega pay-load adapter Arianne V boosters

15. Conclusions • VSP are currently straightforward to manufacture. Their capacity for load redistribution allows for marked improvements on the buckling and failure performances of composite laminates. • The damage models developed are accurate for the prediction of the final failure of VSP in post-buckling. • The critical bucking load of optimized ‘traditional’ laminates can be increased by ~90% using VSP (for roughly the same mass). • The bearing strength and bearing stiffness of the laminate increases with the titanium content (up to 154% for the bearing strength and 32% for the bearing stiffness). Collaboration/funding: