Measurements for Materials Systems (MMS)

MMS13 – Assessment and Criticality of Defects and Damage in Materials Systems

MMS15 – Interactive Knowledge Base (IKB) on NDE and Design of Composites

Minutes of 3^rd Industrial Advisory Group Meeting

Thursday 10^th July 2003

Meeting room CS6, Module 16, NPL

Attendees

Gordon Bishop NetComposites Richard Lee AEAT

John Cantrill VT–Halmatic Bob Lewin Rolls-Royce

Louise Crocker NPL Sam Luke Mouchel

Roger Davidson CTG Rod Martin MERL

Gordon Drummond Imes Ltd Keith McLaughlin Advanced-NDT

Nigel Evans Insys Andreas Obst ESA

Mike Gower NPL Sue Panteny Faraday Advance

Roger Gregory LTI Mark Stone AEAT

Fadhil Habib BAE Systems Martin Wall AEAT

Graeme Hughes HSE Steve Wyatt Quo-Tec Ltd.

Apologies

Peter Padelopoulos (Anvil Innovations), Peter Frewer (Anvil Innovations), Raman Patel (HSE), Steve Austen (RNLI), David Lindsay and Peter Hills (RAF St. Athan), Graham Sims (NPL), Simon Frost (AEAT), Shayz Ikram (L.O.T. – Oriel Ltd.)

1. Welcome and introduction

Mike Gower (MG) welcomed members of the joint IAG to the National Physical Laboratory (NPL) for the third MMS13/15 IAG meeting. He then explained that the intention was to have an industrial chairman for the IAG meetings and that Roger Davidson (RD) had agreed to chair the current meeting (N.B. the project partners are looking for volunteers to chair the next meeting). MG went through the meeting agenda and then asked if anyone had any issues with the minutes from the second IAG meeting. Rod Martin (RM) asked if future minutes could be distributed as ‘pdf’ format. MG then handed over proceedings to RD who asked if members would briefly introduce themselves to the group. N.B. Steve Wyatt (SW) introduced himself and said that he had now replaced Jane Galsworthy as Quo-Tec monitor for the MMS13 and 15 projects.

2. Project progress

2.1 MMS15

Martin Wall (MW) gave an on-line demonstration of the IKB on NDE and design of composites (MMS15). He began by providing a review of some of the key features of the IKB and then gave details of progress made since the last meeting and on the shared notice board for MMS13/15. From the notice board, project reports, minutes from meetings and presentations can be viewed/downloaded. The MMS15 website has a new address http://www.mms15.com and MW said that there is now an IAG members only area (password protected) on the notice board, where draft reports and confidential information can be accessed. This members area can be accessed from the website or directly at http://www.ndt.aeat.co.uk/noticeboards/mms15iag/ . A userID and password is required which can be obtained from Martin Wall from the new generic MMS15 email address info@mms15.com. Access details will be sent shortly by Email to current IAG members.

Gordon Bishop (GB) gave a brief presentation on the work NetComposites have been doing on roll-over menus for the IKB. A demonstration of the menus can be found on the MMS15 web pages at www.mms15.com or currently at the following URL http://www.netcomposites.com/IKB/DefaultDHTML_v01.asp .

2.2 ADMC composite design tools

RL noted that a number of composite design tools accessible via the Internet were now freely and publicly available arising from the recent DTI funded ADMC programme. This includes the AEA Technology developed EngSol – an Interactive Engineering Design Knowledgebase for Composite Materials, available at http://www.admc.aeat.co.uk/ . Other tools were developed by MERL, NPL and others. The main access route to the full suite of tools termed MatSol will be via the NPL website at http://materials.npl.co.uk/matsol/ due to launch in August 2003.

2.3 MMS13

For the benefit of the new IAG members, MG gave a brief overview of the MMS13 project objectives, structure, partners and schedule. He then went on to update the members on the status of the 4 validation case studies that have been sourced for Task 7.

For case study A, CFRP panels that had been subjected to lightning strike (protected and unprotected) had been received from Fadhil Habib (FH). The main types of damage due to the lightning strike were multi-level delaminations, resin burn-out and ply damage. This damage occurred in the top 8 plies but techniques were being identified to check for damage to the resin below this depth. MG reported that some preliminary pulse thermography tests had been performed with LOT-Oriel (Shayz Ikram) and that it was planned to undertake differential scanning calorimetry (DSC) tests on material from the panels to see if damage to the resin could be detected. Case study C had been changed from a marine sandwich construction to a resin infused woven glass system used in the marine sector and for which little damage tolerance data currently existed. Activities in the fourth case study were currently focussing on looking at the most suitable test methods for characterising unidirectional ultra high modulus carbon plates used for bridge strengthening.

MG then proceeded to update members on work being carried out on Task 2 – Experimental testing and Task 4 – Defect Characterisation. MG reported that there had been some delays on these tasks and that now materials from industry were arriving, it was anticipated that testing and characterisation work would progress quickly. MG then presented some recent work that had been undertaken by NPL on the development of damage tolerance testing.

Andreas Obst (AO) commented on the importance of developing residual life test methods for a range of applications in addition to the compression-after-impact (CAI) and tension-after-impact (TAI) methods reported by MG.

Richard Lee (RL) presented work that had been carried out on Task 3 – Non-destructive evaluation assessment. A Task 3 report had been issued in March covering advanced inspection techniques including - ultrasonics (reflection & transmission), radiography (X-ray and g- ray), laser shearography, acoustic emission and thermography. A case study on composite overwrap repairs was described. The simplest technique to investigate defects within and underneath the composite used was a hand-held pulse-echo ultrasonic probe (2.25MHz). However, it was not possible to detect a 5mm diameter hole in the steel pipe under the composite overwrap. More sophisticated versions of the ultrasonic technique (angled twin probes, Time of Flight TOFD) were then assessed Subsequent trials were carried out using a multi-channel digital ultrasonic imaging system. The features of the equipment used were - low inherent noise characteristics, signal averaging noise suppression, long range capability and grey scale imaging with image enhancement. The improved technique allowed the steel/ composite interface to be revealed for the first time.

Mark Stone (MS) updated members on the progress that had been made on Task 5 – Assessment of defect criticality. The main objectives of this task were - identify methods for assessment of criticality, define criteria for acceptability and define framework for assessment. This would directly input into the defect assessment procedure. The task consists of three main elements -

• Investigation of candidate methods for assessment of major defect types (AEAT)
• Definition of experimental approaches for support/validation of defect assessment methods (NPL)
• Evaluation of methods selected for inclusion (AEAT+NPL)

MS reported that most defect types within composite material systems could broadly be characterised as being similar to either delaminations or matrix microcracking. He stated that his assessment of defect criticality had considered these two types of defect only and that a three level approach had been established for criticality assessment. The first level involved a simple assessment, which may be highly conservative, whilst the third level assessment provided for a highly detailed analysis resulting in minimum conservatism. To date the following have been completed :

• Review of available methods for defect assessment
• Definition of methods for inclusion in assessment procedure
• Definition of framework for defect assessment approach
• Evaluation of methods selected for assessment of delaminations

3. Related presentations from industrial partners

After lunch, RD introduced a series of presentations from IAG members. The purpose of the afternoon talks was to provide a chance for members to present work that was related to the MMS13 and 15 projects and to raise issues that were of current concern/importance to industry.

Fadhil Habib (FH, BAE Systems) spoke about the external threats to aircraft structures, in particular low-energy impact, lightning and bird strike. He presented some of the work that he had recently been undertaking with regard to determining allowable damage sizes, repair knowledge and development of a composite repair manual.

Sam Luke (SL, Mouchel) gave a presentation on the West Mill Bridge recently installed in Oxfordshire. The bridge is constructed from pultruded glass fibre (ASSET) profiles that are bonded together. SL gave details on the design, construction, installation and monitoring of the composite bridge.

John Cantrill (JC, VT/Halmatic) presented work on the NDT techniques that are currently used within the VT ship building operations. He provided details on the types of products that VT/Halmatic produce, and the main manufacturing processes and materials that they use. JC reported that most of the NDT techniques that are currently used tend to be relatively simple (visual inspection, tap testing, etc.) and that more sophisticated methods are not used at present.

Bob Lewin (BL, Rolls-Royce) presented recent work on defect detection in static guide vanes used as stators in jet engines. The guide vanes are not subject to significant structural loading and experience reasonably low aerodynamic forces. However, the critical design parameter was for lightweight composite materials that exhibit high natural frequencies, as in-service vibrations arise from complex engine dynamic response. BL mentioned that CAT scans had been used to characterise the materials used and it had accurately quantified the level of porosity in the vanes. However, the technique has not been able to detect in-service damage that occurs, mainly matrix-microcracking, during vibration testing.

Roger Gregory (RG, LTI) provided a detailed description of laser shearography techniques covering aerospace and marine applications. He illustrated this with a range of structures and typical defects that can be detected through a series of case studies Laser Testing (UK) Ltd had undertaken. Further information is available at www.laserndt.co.uk.

The presentations for FH, SL, JC and RG can be viewed on the IAG members only area of the MMS15 web-site http://www.ndt.aeat.co.uk/noticeboards/mms15iag/ or via www.mms15.com along with the presentations given by the project partners. Contact info@mms15.com by Email if you need the UserID and password.

4. Other MMS projects

It was suggested that a list of all the MMS projects should be made available to the IAG. Please see the table below for a list of all the single and competitively tendered MMS projects

Single Tender (NPL)
MMS1.1	Experimental round-robin validations of test methods developed in prior programmes
MMS1.2	Implementation of NPL work as International Standards
MMS2	Towards a standard qualification plan for composite material systems
MMS3	Modelling damage formation in multi-layer systems
MMS4	Validation and design of layered materials systems
MMS8	Interfacial adhesion strength
MMS11	Design for fatigue and creep in joined systems
MMS12	Performance of multicomponent metallics
MMS17	Studio projects in the MMS programme
Competitive Tender
MMS5	Design and failure of material systems under multi-axial loads
MMS6	Composite materials systems in the civil infrastructure
MMS7	Towards and adhesive design toolkit
MMS9	Measurements for efficiency improvements in rapid bonding systems
MMS10	Cure monitoring for shorter cycle times
MMS13	Assessment and criticality of defects and damage in materials systems
MMS15	Interactive knowledge base on NDE and design of composites
MMS16	Macroscale multi-component materials in fire

5. Date of next meeting

The next joint MMS13/15 IAG meeting will be held on the 15^th of January at AEAT, Culham. An agenda will be sent out to members in due course and will be downloadable from www.mms15.com with travel and other details.

Minutes prepared by: Mike Gower and Richard Lee