ASD-STAN PREN 2823-1998 Aerospace Series Fibre Reinforced Plastics Determination of the Effect of Exposure to Humid Atmosphere on Physical and Mechanical Characteristics (Issue P 2.pdf

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1、AECMA STANDARD NORME AECMA AECMA NORM prEN 2823 Edition P 2 November 1998 ICs: PUBLISHED BY THE EUROPEAN ASSOCIATION OF AEROSPACE INDUSTRIES (AECMA) Gulledelle 94 - B-1200 BRUXELLES - Tel. (+32) 2 775 81 1 O - Fax. (+32) 2 775 81 11 Supersedes issue P 1 May 1991 Descriptors: ENGLISH VERSION Aerospac

2、e series Fibre reinforced plastics Determination of the effect of exposure to humid atmosphere on physical and mechanical characteristics Srie arospatiale Luft- und Raumfahrt Plastiques renforcs de fibres Dtermination de linfluence de lexposition latmosphre humide sur les caractristiques mcaniques e

3、t physiques Faserverstrkte Kunststoffe Ermittlung des Einflusses der Auslagerung in feuchtem Klima auf die mechanischen und physikalischen Eigenschaften This “Aerospace Series“ Prestandard has been drawn up under the responsibility of AECMA (The European Association of Aerospace Industries). It is p

4、ublished on green paper for the needs of AECMA-Members. It has been technically approved by the experts of the concerned Technical Committee follo wing comment by the Member countries. Subsequent to the publication of this Prestandard, the technical content shall not be changed to an extent that int

5、erchangeability is affected, physically or functionally, without re-identification of the standard. After examination and signature of the AECMA Standard Checking Centre (NPSI and formal agreement of the Official Services of the Member countries it will be submitted as a draft European Standard to C

6、EN (European Committee for Standardization) for formal vote. Nota - Extra copies can be supplied by B.N.A.E. - Technopolis 54 - 199, rue Jean-Jacques Rousseau - 921 38 ISSY-LES-MOULINEAUX CEDEX Comments should be sent within six months after the date of Dublication to I Edition approved for publicat

7、ion 1998-1 1-30 AECMA Gulledelle 94 I B-1200 BRUXELLES I C7 Chairman Mr Wright aecrna 1998 COPYRIGHT Association Europeene Des Constructeurs de Materiel AerospaceLicensed by Information Handling ServicesSTD-AECMA PREN 2823-ENGL 1998 W 30L233L 0035558 O00 = Page 3 prEN 2823: 1998 1 Scope This standar

8、d specifies the method for determining the effect of exposure to a humid atmosphere on the physical and mechanical characteristics of fibre reinforced plastics. This standard applies to all laminates, whatever the nature of the reinforcement and organic matrix used, unless otherwise indicated in the

9、 material standard and/or technical specification. 2 Normative references This European Standard incorporates by dated or undated reference provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For da

10、ted references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. EN 2743 EN 2744 EN 3615 Aerospace series - Fibre

11、 reinforced plastics - Standard procedures for conditioning prior to testing 1) Aerospace series - Non-metallic materials - Preferred test temperatures Aerospace series - Fibre reinforced plastics - Determination of the conditions of exposure to humid atmosphere and moisture absorption 1) 3 Definiti

12、ons For the purpose of this standard the following definitions apply: 3.1 “Pilot“ specimens Specimens intended to establish the exposure temperature required to achieve an equilibrium condition at the specified humidity level in a limited period of time. 3.2 Specimens “to be aged“ Specimens intended

13、 to determine the mechanical and physical characteristics after exposure. 3.3 “Traveller“ specimens Specimens representative of specimens “to be aged“ which accompany these in the climatic chamber and are intended to monitor moisture absorption. 3.4 Equilibrium condition Condition of the material at

14、 a specified hygrometry when it has reached constant mass. 3.5 Constant mass Mass of the specimen obtained after several successive weighings carried out at regular intervals when the difference between weighings is less than a specified value. 3.6 As-cured condition See EN 2743. 1) Published as AEC

15、MA Prestandard at the date of publication of this standard COPYRIGHT Association Europeene Des Constructeurs de Materiel AerospaceLicensed by Information Handling Services4 Methodology The test results obtained with the specimens in the as-cured condition are compared with those obtained with specim

16、ens “to be aged“ after exposure to the specified humid atmosphere, in accordance with the following procedure: a) as-cured condition (see EN 2743A); carry out the mechanical or physical test according to the appropriate standard on specimens in the b) using pilot specimens determine the highest poss

17、ible exposure temperature guaranteeing a behaviour of the material in conformity with Ficks law (reaching an equilibrium condition). This determination shall be carried out at least once for each case of fibre/resin/temperature combination; c) expose the specimens “to be aged“ to the specified hygro

18、metry and to the temperature as determined above until they reach the equilibrium condition. Traveller specimens shall be permanently subjected to the same exposure conditions; d) 5 5.1 carry out the mechanical or physical tests according to the applicable standards. NOTE: In the preparation of this

19、 standard both Langmuir model and Ficks lauw were considered. While acknowledging that Langmuir Models more exact, Ficks law will be used to define equilibrium conditions in composite materials. A temperature of 70 “C is chosen as the initial verification temperature in order to achieve a reasonable

20、 rate of moisture pick-up. If the pilot specimens results suggest a significant deviation from Flicks law then a lower temperature should be selected. Apparatus Climatic chamber capable of keeping the specified temperature to within f 1 “C and relative .- humidity to within f 3 % 5.2 Desiccator 5.3

21、Balance accurate to within 0,l mg 5.4 Air circulating oven capable of keeping the specified temperature to within k 5 “C 5.5 Clean and dry absorbent cloth or filter paper 5.6 Sealed container: metallized polythene bag or airtight metal or glass enclosure 6 Specimens All the aspects of the manufactur

22、ing process (in particular the surface finish) influence the test results. 6.1 Pilot specimens The panels intended to make up the pilot specimens shall be symmetrically arranged in layers: - unidirectional preimpregnates: unidirectional (O“) or crossed (O“/90) lay-up; - fabrics: all plies warpwise i

23、n the same direction. COPYRIGHT Association Europeene Des Constructeurs de Materiel AerospaceLicensed by Information Handling ServicesSTD-AECMA PREN 2823-ENGL 1778 = LOL2321 00155b0 7b7 = Page 5 prEN 2823: 1998 t The dimensions of the pilot specimens shall be in conformity with figure 1 and table 1.

24、 75 f 1 Figure 1 Table 1 Dimensions in millimetres b 75 f 1 a the lowest possible 6.2 Specimens “to be aged“ (specimens for mechanical and physical tests) The shape, dimensions and manufacturing procedure for the specimens are specified in the materiai standard or test method. They shall be in their

25、 final form, for example, machined, drilled, tabbed, etc. 6.3 Traveller specimens A minimum of three traveller specimens, taken from the same panel as the specimens “to be aged“, but without tabs, holes, etc. shall be used. The traveller specimens shall be rectangular or square, their length and wid

26、th equal to or greater than 25 mm and their mass greater than 1,5 g. The quality of the faces and edges shall be identical to that of the ageing specimens. 7 Procedure 7.1 Conditioning before exposure Specimens to be aged shall not undergo any special conditioning, a condition of equilibrium being t

27、he only criterion sought. COPYRIGHT Association Europeene Des Constructeurs de Materiel AerospaceLicensed by Information Handling ServicesPage 6 prEN 2823: 1998 7.2 Exposure conditions 7.2.1 Standard condition: The humidity level shall be specified. Optional: 7.2.2 Determination of exposure temperat

28、ure It shall be determined on the pilot specimens according to the following procedure: - expose a pilot specimen to the exposure temperature of (70 f 2) OC; - check that the condition of equilibrium has been reached (see 7.2.3) at this temperature; - if this is not the case, expose a new pilot spec

29、imen to a lower temperature chosen from EN 2744; - check that the condition of equilibrium has been reached (see 7.2.3) at this new temperature; - if this is not the case, redo the procedure until a temperature is determined whereby the condition of equilibrium is reached. NOTE 1: If the condition o

30、f equilibrium is reached at 70 OC, a higher exposure temperature may be sought, chosen from EN 2744. NOTE 2: This operation may be replaced by a continuous weighing (therrnobalance type setup) of the pilot specimen in a humid atmosphere. 7.2.3 The total period of exposure for all specimens shall be

31、continued until they reach the equilibrium condition. Constant mass is achieved for test specimens of a thickness of (2 f 0,2) rnm when the difference between three successive weighings carried out at an interval of 168 h on traveller specimens (see figure 2) and in conformity with the formula below

32、: Determination of the condition of equilibrium J where: Mi represents the mean weights of the travellers specimens at the time fi. Figure 2 t (h) If the exposure temperature is less than 70 “C or if the thickness differs from (2 f 0,2) mm, the time interval between two successive weighings to deter

33、mine constant mass shall be obtained by triais; with the value of the difference remaining as above. COPYRIGHT Association Europeene Des Constructeurs de Materiel AerospaceLicensed by Information Handling ServicesPage 7 prEN 2823: 1998 7.3 Exposure to humid atmosphere Place the traveller specimens a

34、nd specimens to be aged in the climatic chamber. The contact between: - the specimens themselves; - the specimens and the walls of the chamber and (or) specimen supports; shall be point contact in order to ensure maximum exposure. 7.4 Monitoring humidity absorption 7.4.1 condensation with the cloth

35、or paper (see 5.5). Remove the traveller specimens from the climatic chamber and wipe them to remove any 7.4.2 Allow them to cool to room temperature in a sealed container to reduce moisture loss to a minimum. 7.4.3 specimens in the equilibrium condition (see 7.2.3). Immediately weigh them to the ne

36、arest 0,l mg. M, is the mean of the weighings of the traveller 7.5 7.5.1 Testing at ambient temperature Remove the specimens “to be aged“ from the climatic chamber and follow the same procedure as in 7.4.1 and 7.4.2. The specimens may be maintained for a maximum of 72 h in a sealed container. The ph

37、ysical or mechanical test shall be carried out according to the relevant standard within the 30 min following removal from the sealed contained. Physical and mechanical tests after exposure 7.5.2 Follow the instructions given in 7.5.1. Place the specimen in the test fixture which has been maintained

38、 at the specified temperature. In order to limit moisture loss but ensure thermal equilibrium, the period between placing the specimen in the fixture and completion of the test shall be as short as possible, while ensuring that the specimen test zone is at the specified temperature. If the test dura

39、tion permits, this period shall be Testing at temperatures other than ambient - less than 15 min, for temperatures ranging from ambient to 50 OC; - less than 5 min, for carbon fibre based specimens of a thickness ranging from 1 mm to 2 mm and for temperatures ranging from 50 “C to 100 OC. For other

40、temperatures, dimensions and materials, if the tests duration does not allow the above mentioned requirements to be met, this period shall be determined by prior test designed to check that the specified temperature is reached at all points subject to an acceptable moisture loss. If it is not possib

41、le to achieve thermal equilibrium with an acceptable moisture loss, use a fixture or chamber which minimises the moisture loss of the specimen during testing. This is essential for lengthy tests such as fatigue or creep, for example. The actual change in moisture level when measuring the characteris

42、tic to be determined, shall be verified with a traveller specimen or calculated according to an agreed mathematical model. Any change shall be recorded to enable interpretation of the test results. COPYRIGHT Association Europeene Des Constructeurs de Materiel AerospaceLicensed by Information Handlin

43、g Services7.6 Dry the traveller specimens in an oven using the sequence: Amount of moisture absorbed by traveller specimens a) 72+20 h at (50k 5) “C ( 0) b) 72+20 h at (70+5) “C ( 0) c) x h at (90 k 5) “C Prior to each weighing allow the traveller specimens to cool down to room temperature in a desi

44、ccator. Moisture pick-up shall be avoided during this operation. Weigh immediately after removal from the desiccator. The drying period x corresponds to the tirne required for the specimens to reach a constant mass. Constant mass being defined as three successive weighings of the traveller specimens

45、 carried out at 72 h intervals (see figure 3) and which complies with the formula below: where: i, represents the mean weights of the travellers specimens at the time ti. Figure 3 If the criterion above is not satisfied, resume drying at c) as many times as necessary M, is the mean of three weighing

46、s, see above, after drying. 8 Expression of results 8.1 Percentage of absorbed moisture (HL) HL = Mq - M2 x 100 M2 where: HL M, M2 is the percentage of absorbed moisture; is the mean of weighings of the traveller specimens at the condition of equilibrium, in grammes; is the mean of weighings of the

47、traveller specimens after drying, in grammes. NOTE: If it is necessary to express the absorbed moisture percentage to a standard resin content, see EN 3615. COPYRIGHT Association Europeene Des Constructeurs de Materiel AerospaceLicensed by Information Handling ServicesSTD-AECMA PREN 2823-ENGL 1998 W

48、 1012311 00155bli 3OLi = Page 9 prEN 2823: 1998 8.2 Influence of moisture on characteristics 8.2.1 Absolute change where: HE is the absolute change in a characteristic due to the exposure; Ri is the mean of the results of the tests obtained on specimens “to be aged“ in the “as cured“ condition and s

49、ubjected to the test at the specified temperature according to the appropriate method; R, is the mean of the results obtained on test specimens after exposure and tested under the same conditions. 8.2.2 Percentage change where: HI is the percentage change of a characteristic due to the exposure; R, is the mean of the results of tests obtained on specimens “to be aged“ in the “as cured“ condition and subjected to tests at the specified temperature according to the appropriate method; R, is the mean of the results obtained on test specimens after ageing and tested under the