Bonding of CFRP primary Aerospace · PDF fileBonding of CFRP primary Aerospace structures...

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Bonding of CFRP primary Aerospace structures Boundary conditions for certification

Presented by

Dipl. Ing. Thomas Kruse, M. Sc., Airframe Design - Research & Technology

June 2013 CFK-Vally Stade Convention 2013 - Thomas Kruse - Airframe Design R&T

© AIRBUS Operations GmbH. All rights reserved. Confidential and proprietary document.

Agenda

Background & motivation

CFRP bonding

Certification requirements

Damage scenarios & technology fields

Design- & technology approaches

Conclusion



mainly build from

Composite (53%)

Introducing Fuselage

stiffened skin out of CFRP

CFK-Vally Stade Convention 2013 - Thomas Kruse - Airframe Design R&T

Introduction

June 2013

Joining Technology is a

key-technology and enabler for

next generation aircraft concepts


Applied joining technologies:


Introduction - Applied joining technologies

June 2013

Joining members Technology

Skin / Stringer Co-Bonding

Skin / Frame (Clip) Bolted Joints

Remark:

≈ 5km Stringer / Skin

Co-Bonded joints

applied per A350


flat Frame / Skin Interface

joined by PI-Joint technology

Skin

Web

PI - Preform

Adhesive

Joining Principle as enabler for new Architectures

Disruptive composite build concept:

The Lockheed-Martin ACCA „Carbon Comet“



Agenda


CFRP bonding




Conclusion




Main driver for joining of composite parts

June 2013

Cost & Lead time

System Integration

Structure

Mechanics

Weight


cured

un-cured

Classification of CFRP-bonding technologies


co-curing:

co-bonding:

secondary bonding:

un-cured

un-cured

cured

cured

adhesive

earl

y i

nte

gra

tio

n

late

in

teg

rati

on

adhesive

adhesive


Main technology fields for bonding for large civil aircraft

Material Qualification

Process safety

NDT / NDI

Design Concepts & Sizing Approach



Agenda


CFRP bonding




Conclusion



Certification boundary conditions acc. AC 20-107B

I. Repeatable and reliable non-destructive inspection techniques

must be established that ensure the strength of each joint.

II. Full single part testing of bonded joints

III. Disbonds of each bonded joint greater than the maximum critical

disbonding must be prevented by design features

Need of advanced special design features

Changing or challenging of this rules is not an option! Airbus/EADS was involved to define the actual regulations based in AC 20-107B.

Bud: regulations are leaving degrees of freedom for improvement.

technology not available

effort not practical

e.g. chicken fasteners



Agenda


CFRP bonding




Conclusion



Bondline failure-types

Failure within Bondline

(Disbond)

Weak bond

(not sufficient adhesion)

Manufacturing Process

Damage of Bondline

(Impact event)

Manufacturing Manufacturing Process

occurr

ence:

Detectable

by NDI/NDT (if > method-threshold)

Implementation of a

suitable Qualitycontrol System

In Service

Addressed by


acc. AC 20-107B

Limitation of Disbond

occurr

ence:

occurr

ence:



Technology fields & damage tolerance

Material Qualification

Process safety

NDT / NDI

Design & Sizing

Capability to handle / avoid (in future): Weak Bonds In Service

Damages

( )



Agenda


CFRP bonding




Conclusion



Design & Technology - approaches


Certification of Bonding


Increase Process Safety

Avoid adhesion as joining

mechanism

Direct contribution

to enable certification


Design & Technology-approach:

Limit Disbond Z-Pinning

Modified Z-Pinning



Additional technology approaches:


Under investigation e.g. within EU Project


Limit Disbond

Surface interfering Features Surface and Geometry

Modification

Mechanical through-thickness

features

Adhesive bondline

architecturing

Identified technology streams:



Basic M&P

Design & Stress

Surface

Preparation

Automation Skills

Technology-approach:






Skin

Web

PI - Preform

Adhesive

Modular Joints (developed e.g. in EU Projects MoJo & CERFAC)

• Joining of two cured

components

• Local Co-Bonding

by uncured (textile)

Joining element

• Different shapes

(e.g. PI / H) investigated



Welding Process Thermoplast - Layer

(Co-cured)

Thermoset Part

Thermoset Part

Activities ongoing - Airbus & EADS-IW with CRC-ACS (Australia) & DLR

No Structural application today


Avoid adhesion as joining mechanism




Avoid adhesion as joining mechanism

Partially un-cured zones – joined by co-curing

Partially cured parts – joined by co-curing


Agenda


CFRP bonding




Conclusion



Roadmap to certification


Certification process safety

NDT capabilities

enabling technologies

design concepts

sizing approach



Today certification of bonded joints w/o additional fasteners is not possible

Further research and technology development needed and addressed at Airbus

New novel ideas & technologies can act as future enabler for secured certification

Process Safety

• Significant Progress

• Still not sufficient for certification w/o fasteners


• Derived from Certification Requirements

• Investigated in EU-Project BOPACS

Alternative joining

mechanism

• Target: Utilize alternative mechanism to adhesion

• Promising technologies under investigation

Conclusion


Thank you for the attention….

Questions?


Dipl. Ing. Thomas KRUSE, M.Sc.

Airframe Design - Research & Technology

Phone: +49 40 743 83469

[email protected]

mailto:[email protected]



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