How NDT will underpin the certification of greener aircraft

Transcription

1 How NDT will underpin the certification of greener aircraft Robert A Smith Professor of NDT and High Value manufacturing, University of Bristol. President British Institute of NDT

2 Acknowledgements Prof Stephen Hallett Dr Luke Nelson Dr Martin Mienczakowski Dr Rostand Tayong Miss Ningbo Xie (PhD student)

3 Content Acknowledgements The Green Challenge Composite materials Non-destructive Testing (NDT) and aircraft design Ultrasound Microscopic 3D imaging NDT-based prediction of strength Conclusions - Will Green Aircraft Fly?

4 The Green Challenge Image: Airbus Image: Rolls Royce

5 Environmental targets: The Green Challenge Advisory Council for Aeronautical Research in Europe (ACARE) target: 50% reduction in CO 2 per passenger-km by 2020 FlightPath 2050 (EU) targets: 75% reduction in CO 2 per passenger-km by % reduction in noise by 2050

6 Source: Road & Rail TREMOVE v3.3.1 (EU countries) Air TRENDS (EU-15 countries) The Green Challenge Transport-mode CO 2 trends projected to 2050

7 The Green Challenge Air CO 2 trends projected to 2050, with targets Source: TRENDS (EU-15 countries)

8 The Green Challenge AIRBUS Concept Plane Fuel-efficient (green) design Longer, slimmer wings reduce drag. Engines at rear and semi-embedded. Reliable, quiet and fuel-efficient. U-shaped tail shields noise. Images: Airbus

9 The Green Challenge Environmentally-friendly Aircraft Low CO 2 emissions Low noise Low fuel burn High speed Low hassle Low-cost flights Perfectly safe Let s look at safety Image: Airbus

10 The amazing safety of air travel Source: Bureau of Aircraft Accidents Archive

11 The amazing safety of air travel Source: Bureau of Aircraft Accidents Archive Source: ICAO

12 The amazing safety of air travel 1/8bn Source: Bureau of Aircraft Accidents Archive Source: ICAO

13 Source: Bureau of Aircraft Accidents Archive Source: ICAO The amazing safety of air travel NDT is not solely responsible for this increase in safety but it is largely the reason why air travel is still affordable and (reasonably) delay-free whilst also being safe.

14 Safety is improving consistently due to: advanced modelling and simulation techniques The amazing safety of air travel rigorous testing of specimens, components and full-scale tests such as on wings

15 Safety is paramount The amazing safety of air travel The absolute level of safety demanded by certifying authorities will not decrease. Manufacturing variations / deviations do not reduce safety because: designs are made stronger to maintain safety levels

16 Why Wouldn t Green Aircraft Fly? NDT will be key to the achievable level of: environmental impact (CO 2, noise, fuel burn, etc) cost (manufacture, maintenance, fuel, etc) reliability / hassle (take-off delays, cancellations) - whilst achieving certification for safe flight. Better NDT opens up the design envelope by: increasing confidence, and reducing uncertainty in performance.

17 Composite materials Increased strength compared with the same weight of metal, allowing weight reduction.

18 Composite materials Carbon-fibre polymer-matrix (plastic) composites. Long fibres made of carbon, embedded in Matrix epoxy (eg Araldite ) 1 mm

19 Composites use a stack of crossed fibres 45 /0 /-45 /90 1 mm Deviations from straight fibres reduce the strength. Composite materials mm

20 Effect of fibre waviness. 6 mm Composite materials TENSION Mukhopadhyay, Jones & Hallett (2013) Full compressive failure 6 mm Just prior to damage Fibre failure in axial ply COMPRESSION Delamination & further fibre failure

21 Composite materials Effect of fibre waviness. Mukhopadhyay, Jones & Hallett (2013) Wrinkle Angle

22 Composite materials How wrinkles are avoided Mould-shape optimisation Rigorous testing and sectioning of specimens Optimum sequence of plies, especially at corners Any remaining wrinkles are compensated by: adding extra plies (thickness) to maintain safety levels

23 Metals are only replaced by composites if: Appropriate properties are considerably improved Other materials Used for a reason Lower cost, or Harder, or Heat tolerant Image: Airbus Material breakdown for an Airbus A350 (Stansbury, 2014) Composite materials

24 AIRBUS composite usage history Image: Airbus

25 Composites Structural Weight [%] Few options for more composite components Maximum number of composite components The future for composites?

26 Non-destructive Testing (NDT) and the design envelope The more we can guarantee that performance of composite will be as expected, the happier the certifying authority will be to certify the lighter designs.

27 Why Wouldn t Green Aircraft Fly? Many of the visionary objectives are in conflict. Most of the technical challenges are expensive. Low emissions conflict with low noise in engines. Low CO 2 High cost High noise Low cost High CO 2 High noise

28 Design goals met by thinner components Less weight Less drag (friction) Less raw material Less fuel Less CO 2 Less noise At what cost? NDT and the design envelope Image: Rolls Royce. Composite fan test-bed.

29 NDT and the design envelope Manufacturing goals for thinner components High quality Confirmed quality High yield (success) High throughput Low cost NDT can help! Image: Boeing

30 NDT and the design envelope

31 NDT and the design envelope

32 NDT and the design envelope

33 NDT and the design envelope The aim: To help meet both design AND manufacturing goals. Thinner components, made faster and cheaper.

34 Ultrasonic NDT

35 Ultrasound Transducers Audible sound Transducers Loudspeaker Microphone Ultrasound Transducers Transmitting Transducer Receiving Transducer

36 Ultrasonic NDT Send pulse F B F B Transducer Defect Specimen Time delay Defects cause echoes that can be detected.

37 B-scan (Brightness Scan)

38 Plot the brightness of the echo at every point. Standard medical image is a B-scan B-scan Presentation

39 Plot the brightness of the echo at every point. B-scan Presentation

40 Plot the brightness of the echo at every point. B-scan Presentation

41 Plot the brightness of the echo at every point. B-scan Presentation

42 Plot the brightness of the echo at every point. B-scan Presentation

43 Microscopic 3D imaging Using ultrasound to probe microscopic structure.

44 Microscopic 3D imaging Ultrasonic vibrations of a composite Composite plies are stacked like resonant tubes. Plies of fibres like tubes. Resin layers like air gaps.

45 Microscopic 3D imaging Ultrasonic vibrations of a composite Measure resonant frequency, calculate ply thickness

46 Ply tracking through ply drops Ply drops can be shown to have a significant impact on laminate strength

47 Ply-drop coupons 3D tracking of resin inter-ply layers X-ray CT: 49 kv, 20 μm voxel size, 4 shots 48

48 Understanding the ultrasonic interaction 3D tracking of resin layers B-scan slice B-scans

49 Understanding the ultrasonic interaction 3D tracking of resin layers

50 Microscopic 3D imaging Ply surface height 51

51 Microscopic 3D imaging In-plane fibre orientation In-plane slice In-plane slice shows Echoes at one time Delay. Variations due to the Fibre bundles. 52

52 Microscopic 3D imaging In-plane fibre orientation In-plane slice In-plane slice shows Echoes at one time Delay. Variations due to the Fibre bundles. 53

53 Microscopic 3D imaging 3D map of Fibre bunches 3D orientation

54 Microscopic 3D imaging 3D map of Fibre bunches 3D orientation Dr Luke Nelson, Research Associate

55 NDT-based prediction of strength

56 NDT-based prediction of strength Predict performance of component. Materials model with actual 3D NDT data inputs Create a volume-element mesh using ply interface heights Populate with fibre directions z y x Miss Ningbo Xie, PhD student

57 NDT-based prediction of strength Modelled failure modes Delaminations Matrix crack (split wood) Fibre kink

58 Miss Ningbo Xie, PhD student NDT-based prediction of strength

59 Miss Ningbo Xie, PhD student Simulation and modelling

60 Composite materials Effect of fibre waviness. Mukhopadhyay, Jones & Hallett (2013) Wrinkle Angle

61 A: amplitude L: wavelength θ: maximum angle Wrinkle Shape Parameters Analysis (thickness-direction) Z (width-direction) y X (fibre-direction) Wrinkle shape along x-direction: Wrinkle shape along y-direction: Gaussian envelope: governs wrinkle volume x Cosine phase: defines wrinkle shape Displacement = Ae x2 W 2 2πx 1 cos L 62 Ultrasonics and NDT Group

62 Wrinkle Shape Parameters Analysis The depiction of two amplitude distributions: decrease continuously Gaussian reduction: A i = Ae i i mid 2 /n 2 4-Interface Group reduction: 1.0:0.63:0.39: decrease continuously Ultrasonics and NDT Group

63 Compression Failure Stress Knock-down (MPa) Knock-down of failure stress: Wrinkle Shape Parameters Analysis For a wrinkle region with fixed volume, maximum angle is the major parameter for determining compression strength. Gaussian reduction: A i = Ae i i mid 2 /n 2 4-Interface Group reduction: 1.0:0.63:0.39:0.0 Knock-down = tested pristine value (643.5 MPa ) - model value 64 Ultrasonics and NDT Group

64 Composite materials The future 3D mapping and modelling of Porosity Further gains in weight due to extra confidence

65 Summary

66 Reducing weight Increased confidence at the design stage allows: better understanding of the effect of defects designs that reduce weight, fuel and CO 2 design for low inservice maintenance

67 Reducing weight Increased confidence at manufacture allows: confirmation of conformance to design less need for extra thickness/weight to mitigate risk process-control feedback to increase manufacturing yield

68 Conclusions New, green aircraft will fly; but how green? how expensive? Depends on increased confidence in: optimised designs. conformance to design at manufacture The future: 3D mapping of internal microscopic properties Certification of lighter designs, low CO 2 emissions.