STELIA AEROSPACE NORTH AMERICA - · PDF fileThis document and all information contained herein is the sole property of STELIA Aerospace. ... for aerostructure ... – Standoff failed

This document and all information contained herein is the sole property of STELIA Aerospace. This document shall not be

reproduced or disclosed to a third party without the express written consent of STELIA Aerospace.

STELIA AEROSPACE

NORTH AMERICA

SPACE QUALIFIABLE BONDED JOINTS

BETWEEN CARBON FIBER

REINFORCED POLYMER (CFRP) AND

ALUMINUM

SOHEILA MAHDAVI



Outline

2

1• Stelia Presentation

2

• Carbon Fiber Reinforced Polymer Composites (CFRP)

3• Objective

4• Requirements specification

5• Qualification Tests

6• Manufacturing and testing of Prototypes

7• Conclusion



STELIA Worldwide

> 6,400 employees

$ 2,5 billion revenue

$ 210 million R&D

N°1 in Europe

for aerostructure

N°3 worldwide

for first and business

class seats

N°1 worldwide

crew seats

N°3 worldwide

for aerostructure

STELIA Group, an aerospace multi-specialist3



• 6,400 employees

– 4,600 in France

with 3 main production sites & 600 in engineering

– 1,000 in North Africa

– 600 in North America

– 5 fully owned Airbus subsidiaries

Commercial deskManufacturing

STELIA Group, a global presence

4



5

STELIA North AmericaLunenburg Facility

Composite ManufacturingMirabel Facility-

Assembly and Systems installation

Mirabel Facility Composite Manufacturing



• Design and build

• Plug & Fly (includes systems)

• Supply chain management optimization

BOMBARDIER Global 7000 / 8000

6



The Competitive Challenge• The Space and Aerospace Industry are directed more heavily than in the

recent past towards:

> new materials;

> lower prices;

> faster manufacturing cycles

> production innovation

• The challenge for Stelia to grow its market share is to develop innovative

manufacturing techniques that are consistent with existing and future

customer demands.

• The challenge is not only from a technology standpoint but also from a

financial standpoint in:

> people,

> Time

> willingness to invest in R&D.

7



Carbon Fiber Reinforced Polymer

Composites (CFRP)

• Advantages:

– High strength

– Light weight

– Dimensional stability under large temperature variations

• Challenges:

– rarely form the totality of the structure and still need to be assembled with metallic parts:

> Titanium

– thermally stable under a large range of temperature

– expensive

– more complex to manufacture

> Aluminum

– commonly used metallic parts for space applications

– CTE completely differs from CFRP’s

» dimensional issues under the influence of a varying temperature

8



Project Objective

9

Select adhesives and associated bonding processes

To bond Carbon Fiber Reinforced Polymer (CFRP) and aluminum

For the Canadian Space Agency (CSA)



Requirements specification

• Phase I:

– Literature review

– Selection, identification and analysis of adhesives

> <1.0% TML (Total Mass Loss)

> <0.1% CVCM (Collected Volatile condensable Material)

> < 10% bonding strength and stiffness variation at -170 ˚C < T <160 ˚C

– Design and fabrication of test coupons for characterization of the

adhesives and bonding processes

– Test the coupons to measure and characterize the bonding strength

and stiffness over the specified temperature range.

10



Requirements specification

• Phase II:

• Bonded joint prototype development and qualification

– Design three CFRP-aluminum on a

> CFRP plate

> CFRP strut

> CFRP tube

– Development of bonding procedure

– Procurement/manufacturing of the prototypes

– Thermal-vacuum (T-Vac) testing of each prototype and verify its bonding

– Random vibration testing to test the bonds

11



Qualification tests on coupons

• Flatwise tensile test (ASTM D7291)

– Thick laminate (0.46”) tested at room temperature ambient (RTA)

> failure mode within ply

• Lap-shear adhesion (ASTM D5868)

– aluminum bonded to CFRP with adhesives tested at:

> room temperature ambient (RTA),

> cold temperature dry (CTD) : -70˚C,

> elevated temperature dry (ETD) : +160 ˚C.

• Adhesive selection based on qualification test results:

– film adhesive 1

– film adhesive 2

– film adhesive 3

– film adhesive 4

12



Manufacturing of the prototypesPrototype 1: aluminum part bonded on a flat CFRP plate

13

Use G10 sheets to avoid bagging under the mass and around the standoff during curing in the autoclave

Prototype 1 (consisting of 16 plies cured in OA )

Standoffs after curing Broken standoff



14

Manufacturing of the prototypesPrototype 2: aluminum end fitting on a CFRP strut

The layup mold on a turning fixture 8 plies of CFRP on the adhesive and the mold

Final Part



15

Manufacturing of the prototypesPrototype 3: aluminum end-fitting on a CFRP tube

A mold is required for manufacturing a tube

out of composites

The mold-fixture with the endfitting,Two layers of adhesive 3 on the end fitting,Sixteen layers of CFRP on the adhesive and the mold.

Final Part



Prototypes testing

• T-Vac testing

– Vacuum test at 0.00005 Tor

– Thermal cycling

> Number of cycles: 10 cycles

> Temperature range -160°C to +140°C

> Tolerances: Cold: -10°C, +0°C / Hot: -0°C, +5°C

> Minimum time at plateau: 30 minutes

> Maximum rate of change: 10°C/min.

– Three prototypes are placed on a solid

aluminum plate inside the chamber.

16



Inspection after TVAC test

• After TVAC, a visual inspection of three prototypes is performed.

• There is no apparent damage in the CFRP or the bondline for

prototype 1. Prototype 1 passed the test.

• One standoff seems to be weakened due to stress concentration.

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Inspection after TVAC test (Cont.)

• For prototype 2: there was no apparent damage in the CFRP or the

bondline.

• Prototype 2 passed the test.

18



Inspection after TVAC test (Cont.)

• For prototype 3:

– there was no apparent damage in the CFRP or the bondline from the

outside.

– Debonding observed from the insdie.

• Prototype 3 failed the test.

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Random vibration

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• Tests were performed at DFL:

– 40,000 lbf capacity shaker

– 150 GRMS acceleration limit

– 37,000 lb force limit

– Mass of slip table is 593.2 lb

– Test plan:



21

Random vibration

Prototype 1: Two stand-offs broke during adhesive cure

Prototype 2 Prototype 3



Random vibration

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• Prototype 3

– Evidence of failure in adhesive



Random vibration

• Results summary

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Conclusion

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• Three prototypes were design and manufactured.

• Co-curing endfitting with adhesive 3 and prepreg was successful.

• Prototypes 1 and 2 passed the TVAC test.

• Prototype 3 failed the TVAC test.

• Random vibration test for prototype 1 is not conclusive:

– Standoff failed before reaching 50% load level.

• Prototype 2 passed random vibration test.

• Random vibration for prototype 3 is not conclusive.

– There was initial failure in the bondline after TVAC.

• Adhesive 3 can be used for bonding aluminum to CFRP for space

application:

– The successful application will depend on the bondline size.

– There is a critical bondline size/surface area above which thermal

stresses cause failure in the bondline.



Thank You

25



Preselection of adhesives

• pre-selected film adhesives to be tested during Phase I:

– film adhesive 1

– film adhesive 2

– film adhesive 3

– film adhesive 4

• The CFRP laminates:

– quasi-isotropic layup

– Plain weave fabric

– Resin: Toughened epoxy

26



Flatwise tensile strength

• Flatwise tensile strength per ASTM D7291.

• Coupon dimensions: D=1” thickness 0.1”.

• Flatwise tensile results:

– Three coupons: 4257 psi, 4287 psi, and 4651 psi.

29-MAR-17CSA – PT9 - CAL-15-101 27



Assessment of results

• Materials set validation:

– FW tensile strength: min of 4257 psi > 2500 psi -> Pass.

– Lap-shear strength: min of 3548.6 psi > 2000 psi -> Pass.

• Inspection of CFRP aluminum joint prototypes:

– Prototype 1: Pass (Not conclusive).

– Prototype 2: Pass.

– Prototype 3: Fail.

29-MAR-17CSA – PT9 - CAL-15-101 28



Random vibration

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• Prototype 1

– Two stand-offs broke during adhesive cure



Random vibration

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• Prototype 2

– Vibration test setup



Random vibration

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• Prototype 2




Random vibration

32

• Prototype 3




Random vibration

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• Prototype 3




Design, analysis and R&D in advance composite structures

Long term partnership with NRC. NRC co-located with Stelia in Mirabel

Automated Fiber Placement

Manufacturing Space structures

Clean Room 8,000 sqft, Class 100,000

Autoclave 6 feet diameter x 20 feet long

Reticulation Machine 56x96

Mirabel Facility+ 35,000 sqft

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STELIA AEROSPACE NORTH AMERICA - · PDF fileThis document and all information contained herein is the sole property of STELIA Aerospace. ... for aerostructure ... – Standoff failed