Bsi bs en 03745 410 2015

4.4 Procedure 4.4.1 Initial measurements If the value of the highest temperature value is not specified in the product standard make a quick estimation of the highest test temperature

BSI Standards Publication

BS EN 3745-410:2015

Aerospace series — Fibres and cables, optical, aircraft use — Test methods

Part 410: Thermal life

National foreword

This British Standard is the UK implementation of EN 3745-410:2015

It supersedes BS EN 3745-410:2007 which is withdrawn

The UK participation in its preparation was entrusted to Technical Committee ACE/6, Aerospace avionic electrical and fibre optic technology

A list of organizations represented on this committee can be obtained on request to its secretary

This publication does not purport to include all the necessary provisions of a contract Users are responsible for its correct application

© The British Standards Institution 2015 Published by BSI Standards Limited 2015

ISBN 978 0 580 88562 4 ICS 49.060

Compliance with a British Standard cannot confer immunity from legal obligations.

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 July 2015

Amendments issued since publication

BS EN 3745-410:2015 EUROPEAN STANDARD

NORME EUROPÉENNE

EUROPÄISCHE NORM

July 2015

English Version

Aerospace series - Fibres and cables, optical, aircraft use - Test

methods - Part 410: Thermal life

Série aérospatiale - Fibre et câbles optiques à usage

aéronautique - Méthodes d'essais - Partie 410 : Durée de

vie en température

Luft- und Raumfahrt - Faseroptische Leitungen für Luftfahrezuge - Prüfverfahren - Teil 410: Lebensdauer unter

Temperatureinwirkung

This European Standard was approved by CEN on 14 February 2015

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member

This European Standard exists in three official versions (English, French, German) A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom

EUROPEAN COMMITTEE FOR STANDARDIZATION

C O M I T É E U R O P É E N D E N O R M A L I S A T I O N

E U R O P Ä I S C H E S K O M I T E E F Ü R N O R M U N G

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2015 CEN All rights of exploitation in any form and by any means reserved

worldwide for CEN national Members

Ref No EN 3745-410:2015 E

Contents

Page

Foreword 3

1 Scope 4

2 Normative references 4

3 Test specimens 4

3.1 Fibre ends 4

4 Method A (without mechanical stress applied) 4

4.1 Preparation of test specimens 4

4.2 Test conditions 5

4.3 Apparatus 5

4.4 Procedure 5

4.4.1 Initial measurements 5

4.4.2 Test 5

4.4.3 Final measurements and requirement 6

4.4.4 Special precautions 6

5 Method B (with mechanical stress applied) 6

5.1 Preparation of test specimens 6

5.2 Test conditions 6

5.3 Information to be included in the product standard 6

5.4 Apparatus 7

5.5 Procedure 8

5.5.1 Initial measurements 8

5.5.2 Test 8

5.5.3 Calculation of the regression line 9

5.5.4 Special precautions 10

6 Requirements 10

BS EN 3745-410:2015

EN 3745-410:2015 (E)

3

European foreword

This document (EN 3745-410:2015) has been prepared by the Aerospace and Defence Industries Association

of Europe - Standardization (ASD-STAN)

After enquiries and votes carried out in accordance with the rules of this Association, this Standard has received the approval of the National Associations and the Official Services of the member countries of ASD, prior to its presentation to CEN

This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by January 2016 and conflicting national standards shall be withdrawn at the latest by January 2016

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights This document supersedes EN 3745-410:2007

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom

1 Scope

This European Standard specifies a method of measuring the thermal endurance of a finished optical cable There are two test methods incorporated which estimate the cables thermal life with or without the mechanical stress

 Method A – without mechanical stress (temperature only),

 Method B – combined temperature and mechanical stress

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application For dated references, only the edition cited applies For undated references, the latest edition of the referenced document (including any amendments) applies

EN 2591-100, Aerospace series — Elements of electrical and optical connection — Test methods — Part 100:

General

EN 3745-100, Aerospace series — Fibres and cables, optical, aircraft use — Test methods — Part 100:

General

EN 3745-301, Aerospace series — Fibres and cables, optical, aircraft use — Test methods — Part 301:

Attenuation

ASTM-D3032, Standard test methods for hookup wire insulation 1)

3 Test specimens

3.1 Fibre ends

The fibre ends shall be prepared in accordance with EN 2591-100

If not yet at standard test conditions, the specimens shall be subjected to standard test conditions and stabilized at these conditions for 24 h as defined in EN 3745-100

4 Method A (without mechanical stress applied)

4.1 Preparation of test specimens

Specimens have to be fixed on an apparatus representative of aircraft installation Ten specimens are fixed on apparatus and constitute a set for life testing at each temperature A minimum of four sets of specimens is necessary

1) Published by: ASTM National (US) American Society for Testing and Materials (http://www.astm.org/)

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4.2 Test conditions

The following details shall be specified if not already included in the product standard:

 Type of fibre/cable from which the specimens were taken,

 Type/number/pitch of clamps

 Minimum authorized long term bend radius

 Length of specimens if not 10 m

 Maximum permissible variation in attenuation if not −3 dB

 Temperature values (θ1 > θ2 > θ3 > θ4)

4.3 Apparatus

The apparatus shall comprise:

 A Light Launch System (LLS) as defined in EN 2591-100,

 A split coupler 1 × 10,

 A Light Detection System (LDS) as defined in EN 2591-100, with 10 channel recorder,

 A fixture to secure the specimens,

 A climatic chamber capable of temperature control of ± 2 °C

4.4 Procedure

4.4.1 Initial measurements

If the value of the highest temperature value is not specified in the product standard make a quick estimation of the highest test temperature with one specimen during 24 h at 80 °C above the nominal rating temperature The variation in attenuation shall not exceed the specified value

4.4.2 Test

The attenuation shall be monitored throughout the test in accordance with EN 3745-301, method C

Connect the specimen ends to the coupler, the coupler to LLS and the other specimen ends to LDS

Place the fixture in the test chamber The coupler and connectors shall not be into climatic chamber

Begin the test sequence with the highest test temperature (θ1) since exposure times will be relatively short Record the exposure time to failure for each specimen A failure is defined when the variation in attenuation is higher than the specified value

Stop the test sequence when all specimens in group have failed

Calculate the log average life as defined in ASTM-D3032 If the log average life at this temperature (highest)

is found to be less than 100 h, too high a test temperature has been selected and these data should be discarded Tests should be repeated at lower temperature

Repeat this procedure with the group N° 2 of specimens for θ2 temperature value

Calculate the log average life as defined in ASTM-D3032

Repeat this procedure with the group N° 3 of specimens for θ3 temperature value

Calculate the log average life as defined in ASTM-D3032

Repeat this procedure with the last group of specimens for θ4 temperature value (lowest)

Calculate the log average life as defined in ASTM-D3032 If the average life found at this test temperature is less than 5 000 h, this test will be made at lower temperature

4.4.3 Final measurements and requirement

The calculation of average life and extrapolation are defined in the ASTM-D3032 — Standard test methods for hookup wire insulation

4.4.4 Special precautions

Extrapolation to a temperature index expected at the selected end of life (10 000 h, 20 000 h or 40 000 h) should not exceed 25 °C below the lowest aging test temperature

 The log average life at the highest test temperature (θ1) shall not be less than 100 h

 The log average life at the lowest test temperature (θ4) shall not be less than 5 000 h

5 Method B (with mechanical stress applied)

5.1 Preparation of test specimens

One set for life testing shall consist of ten specimens fixed on the apparatus (Figure 1) at each temperature A minimum of four sets of specimens is necessary In order to reduce the variation of stress to the fibre the cable shall be attached to the test fixture by trapping it between two padded plates rather than using standard aircraft cable clamps

5.2 Test conditions

Length of specimens 5 m

Length of specimens within the test chamber 3 m

Maximum permissible variation in attenuation if not 3 dB at 20 °C ± 3 °C and at 850 nm

Launch conditions to be 85/85

5.3 Information to be included in the product standard

 Type of fibre/cable from which the specimens were taken,

 Minimum long term bend radius (R),

 wave length if not 850 nm,

 Maximum permissible variation in attenuation if not 3 dB,

 Launch conditions if not 85/85

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5.4 Apparatus

The apparatus shall comprise:

 A Light Launch System (LLS) as defined in EN 2591-100,

 A Light Detection System (LDS) as defined in EN 2591-100,

 A device allowing to connect the LLS to all specimen shall be used to focus the test on the ageing of cable,

 A device allowing measuring one of the specimens or all cable without disconnection shall be used in order to keep the baseline of initial measurement

A test fixture is used to secure the specimens, this fixture shall be so designed that the cable is mounted so that it can be bent at 90° either side of its centre line and is free to freely follow a curve between the two clamp

points that corresponds to it minimum bend radius (D = 2R) The test sample is to be so arranged that only the

portion of the sample in the flexing area is stressed during the test The fixtures corner is to be rounded and padded see Figure 1 and Figure 2

A climatic chamber capable of temperature control of ± θ2 °C

Key

1 To the LLS

2 To the LDS

3 Fixed plate

4 Moving plate

D = is twice the cable minimum bend radius

R = not less than the minimum bend radius least

Figure 1 — Test Fixture

Key

1 Plate

2 Cable

3 Silicon rubber foam

Figure 2 — Fixture radius and padded edges

5.5 Procedure

5.5.1 Initial measurements

If the highest test temperature value is not specified in the product standard make an evaluation of the highest test temperature with one specimen during 24 h at 80 °C above the nominal rating temperature This evaluation needs to be done at temperatures below the degradation temperature of raw materials used in the cable under test

The jacket shall not fail or the variation in attenuation shall not exceed the specified value in which case repeat the test at a lower temperature

5.5.2 Test

The attenuation shall be measured at the end of each exposure cycle in accordance with EN 3745-301, method C

Connect the specimen ends to the LLS and the other specimen ends to LDS during all the cycles

Place the fixture in the test chamber The connectors shall not be in the climatic chamber

Measure the attenuation of each test specimen

Begin the test sequence with the highest test temperature (θ1) since exposure times will be relatively short Expose the specimens for the first test cycle

NOTE This measurement is for reference only and does not form part of the qualification testing

To monitor the behaviour of the cable/s under test at high temperature, an attenuation measurement of each cable shall be made at the maximum point of the high temperature cycle immediately prior to reducing the temperature to ambient

On completion of the exposure period allow the specimen to return to ambient

Bend the specimen to 90o once in each direction then return the specimen to the neutral position before measuring the attenuation value

Inspect the cable jacket in the bend area for major cracks or splits without disturbing the cable

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Start the next exposure cycle

Record the number of exposure cycles to failure for each specimen A failure is defined when the variation in attenuation is higher than the specified value or the jacket splits or cracks The life of each specimen is defined as the number of cycles to failure times the length of each cycle

Stop the test sequence when all specimens in the set have failed

Calculate the log average life as defined in ASTM-D3032 If the log average life at this temperature (highest)

is found to be less than 100 h, too high a test temperature has been selected and these data should be discarded Tests should be repeated at lower temperature

Repeat this procedure with the group N° 2 of specimens for 2 temperature value

Calculate the log average life as defined in ASTM-D3032

Repeat this procedure with the group N° 3 of specimens for 3 temperature value

Calculate the log average life as defined in ASTM-D3032

If the calculated regression line does not indicate a life of less than 40 000 h at a temperature less than 30 °C below the test temperature repeat this procedure with another group of specimens at temperature not greater than 30 °C above the calculated 40 000 h temperature

5.5.3 Calculation of the regression line

It has been established that many materials deteriorate in a manner so that the following equation applies:

L = Ae b/K

where

L is the insulation life;

K is the absolute temperature (in kelvins);

A, b are constants for each insulation;

e is the base of natural logarithms

Equation may be expressed as a linear function by taking logarithms:

log L = log A + b/K

Let

Y = log L

a = log A

X = 1/K

Then

Y = a + bX