Improving In-Service Inspection of Composite … In-Service Inspection of Composite Structures ... Jim Hofer - Boeing Jeff Kollgaard ... • Detection of matrix micro cracking hidden

FAA Hughes Technical Center

Dennis RoachSandia National Labs

FAA Airworthiness Assurance Center

Improving In-Service Inspection of Composite Structures

CACRC Damage Assessment & Quality Inspection Task Group Update

Improving In-Service Inspection of Composite Structures

CACRC Damage Assessment & Quality Inspection Task Group Update


ITG Team ParticipantsITG Team Participants

CACRC Inspection Task Group Members:

John Hewitt – Airbus (Co-chair)Jim Hofer - BoeingJeff Kollgaard – BoeingKirk Rackow - Sandia Labs AANCDennis Roach - Sandia Labs AANC (Co-chair)Glae McDonald - US AirwaysDarrell Thornton – UPSRichard Watkins - Delta Air LinesBob Stevens – United AirlinesEric Bartoletti – American Airlines Alex Melton - Northwest AirlinesAna Tocalino - Embraer

Dave Galella, Al Broz, Rusty Jones, Larry Ilcewicz – FAA


• Composite NDI Handbook– Complete (SAE ARP5089); requires update

• Industry wide NDI Reference Standards– Complete (SAE ARP5506 & 5507; DOE report distributed in

June 2004)

• NDI Assessment: Honeycomb Structures– Experiments completed in 2007– DOT report in progress

• NDI Assessment: Solid Laminate Structures– Experiment development completed

• Miscellaneous Ongoing and Planned Studies– Detection and quantification of weak bonds– Affect of porosity, repairs & other impediments on NDI– As required to support main tasks & other task groups

CACRC Inspection Task Group ActivitiesCACRC Inspection Task Group Activities


Composite Inspection Reference Standards

Composite Inspection Reference Standards

• Industry-wide composite reference standards developed to support damage assessment & inspection – honeycomb & solid laminate

• SAE Aerospace Recommended Practices (ARP 5605 & 5606) - adopted into Boeing and Airbus NDT Manuals

• Improve inspections of composite structures via introduction of advanced NDI methods

• Provides consistent approach to composite inspections - harmonized approach by OEMs worldwide

Optimized NDT Reference Standards

Assessed all construction scenarios and determined the variables that affect NDI – final

NDI Reference Standards designed accordingly


Composite HoneycombFlaw Detection ExperimentComposite Honeycomb

Flaw Detection Experiment

1) how well current inspection techniques are able to reliably find flaws in composite structures

2) the degree of improvements possible through the integration of more advanced NDI techniques and procedures.

Utilize airline inspectors to establish industry-wide performance curves that quantify:

• Statistically relevant and realistic flaw profiles• Blind application of techniques to study hits, misses,

false calls, and flaw sizing


S-9 Sondicator (LFBT)V-95 Mechanical Impedance Analysis

Conventional NDI Devices

Automated Tap HammerManual Tap Hammer


Thermography

MAUSSystem

SAM System

Shearography

Wide Area and C-Scan Inspection MethodsWide Area and C-Scan Inspection Methods

PE Phased Array UT UT Wheel Array

UltraImage Scanner


MAUS Image

Shearography (LTI) Image

Ultrasonic Wheel Array

SAM Image

Thermography (TWI) Image


Performance of Multiple Devices forA Single Type of Test Specimen

Performance of Multiple Devices forA Single Type of Test Specimen

Results - evaluate performance attributes1) accuracy & sensitivity (hits, misses, false calls, sizing)2) versatility, portability, complexity, inspection time (human factors)3) produce guideline documents to improve inspections4) introduce advanced NDI where warranted

Comparison of Advanced Inspection Techniques withBest Conventional NDI Result on 9 Ply Carbon

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Flaw Size (Dia. in Inches)

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Thermography MAUS IV Shearography CATT S.A.M. Wichitech DTHFalse Calls 744000 4.4


Cumulative PoD - Woodpecker for All Panel Types

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3 Ply Fiberglass


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3 Ply Fiberglass 3 Ply Carbon


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3 Ply Fiberglass 3 Ply Carbon 6 Ply Fiberglass


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3 Ply Fiberglass 3 Ply Carbon 6 Ply Fiberglass 6 Ply Carbon


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3 Ply Fiberglass 3 Ply Carbon 6 Ply Fiberglass 6 Ply Carbon 9 Ply Fiberglass


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Performance of Single Device (Woodpecker)Over Range of Test Specimen Types

Performance of Single Device (Woodpecker)Over Range of Test Specimen Types


Purpose• Determine in-service flaw detection capabilities: 1) conventional NDT

methods vs. 2) improvements through use of advanced NDT. • Optimize laminate inspection procedures.• Compare results from hand-held devices with results from scanning

systems (focus on A-scan vs. C-scan and human factors issues in large area coverage).

• Provide additional information on laminate inspections for the “Composite Repair NDT/NDI Handbook” (ARP 5089).

An Experiment to Assess Flaw Detection Performance in Composite Laminate Structures

An Experiment to Assess Flaw Detection Performance in Composite Laminate Structures

A380 Section 19

737 Composite Horiz. Stabilizer


Thick Laminate With Complex & Simple TaperThick Laminate With Complex & Simple Taper


Specimen Set - Flaw Detection in Solid Laminate Composites

Specimen Set - Flaw Detection in Solid Laminate Composites

Thickness Range:12 – 64 plies

Simple Tapers

Complex tapers

Substructure Flaws

Curved Surfaces

Array of flaw types

NDI Ref. Stds.


Composite NDI & Laminate Repair Systems –Compare Mechanical & NDI Performance

Composite NDI & Laminate Repair Systems –Compare Mechanical & NDI Performance

Comprehensive evaluation of composite repair and associated NDI technology to ensure proper mesh between structural integrity & flaw detection

Strain field & repair efficiency assessment vs.

NDI findings

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Repaired Panel #9Ultimate Failure Test

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Uniform Axial Strain Outside of Repair

Strain at Center of Patch

Strain at Edge of Patch

Strain in Patch - Solid Geometric ShapesSrain in Parent Material - Open Geometric Shapes

Strain Next to Patch

Ultrasonic C-Scan

Uniaxial carbon graphite; plies plus one repair


Use of NDI to Quantify Porosity Levels & Assess Mechanical Properties vs. PorosityUse of NDI to Quantify Porosity Levels &

Assess Mechanical Properties vs. Porosity

• Intercompare mechanical tests, NDI & acid etch methods to assess porosity, strength and fatigue life

• Use of NDI tests to calculate mechanical properties

• Use of advanced NDI to improve quantification of porosity (stratified porosity that may exist in a repair)

Carbon Weave


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Pristine -Best

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30% MR Dilution

70% MRDilution

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66% MRScreen

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33% MRScreen

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100 MR

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Room Temp.

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Characterize Bonded Joints:Quantify Adhesive Strength

Characterize Bonded Joints:Quantify Adhesive Strength

TTU of Weak Bond Specimens Show Trends


Angle Beam Ultrasonic Spectroscopy (ABUS)Angle Beam Ultrasonic Spectroscopy (ABUS)

• Compare received and transmitted waveforms in frequency domain; study frequency/amplitude shifts & change in damping in FRF

• Oblique wave (broadband UT beam) introduces shear stress in the bond line

• Difference between longitudinal wave and shear wave interrogation

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Bad bondGood bond

Normal incidence reflection coefficient

Frequency (MHz)

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Bad bondGood bond

10Frequency (MHz)

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Oblique incidence reflection coefficient

Frequency and Amplitude Shifts Differentiate Bonds

Negligible Affects on Normal Wave (?)


Future Direction of CACRC Damage Assessment & Quality Inspection Task Group


• Detection of Barely Visible Impact Damage (BVID); determining extent of composite damage → driven by visual detection

• Enhanced visual inspection• Inspection of scarfed composite repairs; in-process QA• Inspection of fastened repairs to composite structure (in-

process QA; no current post-repair NDI requirement)• NDI vs. Damage Tolerance vs. Residual Strength – assess

structural integrity (focus on particular materials?)• NDI of adhesive bonds (“kissing” disbonds; weak bonds)• Ascertaining deterioration of material properties due to

environmental exposure (temp., moisture, chemicals, stress)




• Detection of fluid ingress• Quantification of porosity (ref. stds. are critical)• Detection of matrix micro cracking hidden beneath painted

surfaces• Rapid, large area inspection methods (improve POD; decrease

false calls)• Methods to inspect highly attenuative materials (weaves, thick

structures, multi-layered structures) – proprietary issues?• Utilization of SHM techniques• Evaluating NDI performance - assessing conventional NDI in

light of advanced NDI methods




• Optimization of NDI procedures; improved documentation and guidance

• Training – knowledge of hardware & procedures; use of “qualification standards”; industry standardization

• Ramp NDI – qualified personnel; equipment availability• Implement a database – trends assessment


CACRC Inspection Task Group Update and Overview

CACRC Inspection Task Group Update and Overview

Dennis RoachSandia National Labs

FAA Airworthiness Assurance Center(505)844-6078

[email protected]

Documents

Improving In-Service Inspection of Composite … In-Service Inspection of Composite Structures ... Jim Hofer - Boeing Jeff Kollgaard ... • Detection of matrix micro cracking hidden