1、AECMA STANDARD NORME AECMA AECMA NORM Edition approved for publication prEN 4238 Edition P 1 February 1998 C7 Chairman Comments should be sent within six months after the date of publication to PUBLISHED BY THE EUROPEAN ASSOCIATION OF AEROSPACE INDUSTRIES (AECMA) Gulledelle 94 - 8-1200 BRUXELLES - T
2、el. (+32) 2 775 81 10 - Fax. (+32l 2 775 81 11 ICs: Descriptors: ENGLISH VERSION Aerospace series Fibre reinforced plastics Determination of the effect of dry heat on physical and mechanical characteristics Srie arospatiale Luft- und Raumfahrt Plastiques renforcs de fibres Dtermination de linfluence
3、 de la chaleur sche sur les caractristiques physiques et mcaniques Fasewerstrkte Kunststoffe Bestimmung des Einflusses trockener Hitze auf die physischen und mechanischen Eigenschaften This “Aerospace Series“ Prestandard has been drawn up under the responsibility of AECMA (The European Association o
4、f Aerospace Industries). It is published on green paper for the needs of AECMA-Members. It has been technically approved by the experts of the concerned Technical Committee following comment by the Member countries. Subsequent to the publication of this Prestandard, the technical content shall not b
5、e changed to an extent that interchangeability is affected, physically or functionally, without re-identification of the standard. After examination and signature of the AECMA Standard Checking Centre (NPS) and formal agreement of the Official Services of the Member countries it will be submitted as
6、 a draft European Standard to CEN (European Committee for Standardization) for formal vote. 1998-02-27 AECMA Gulledelle 94 I 6-1 200 BRUXELLES I Mr Wright aecma 1998 Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMANot for ResaleNo rep
7、roduction or networking permitted without license from IHS-,-,- STDmAECMA PREN q23-ENGL 1998 LOL23LL 0011i33b 790 m Page 2 prEN 4238: 1998 Contents Page O 1 2 3 4 5 6 7 8 9 10 11 12 Foreword . 3 Scope . 3 Normative references 4 Definitions . 4 Principle . 4 Apparatus 5 Test specimens and samples . 6
8、 Conditioning before exposure 7 Procedure 8 Expression of results . 8 Designation . 11 Exposure conditions 7 11 Annex A . 12 Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMANot for ResaleNo reproduction or networking permitted without
9、 license from IHS-,-,-O STD-AECMA PREN 9238-ENGL LA W LO323L3 0034337 b27 a Page 3 prEN4238: 1998 Foreword Fibre reinforced plastic materials are sensitive to effects of heat; the temperature level and the length of time they are exposed to heat lead to a change or even a deterioration in the physic
10、al, chemical and mechanical properties of the material. The behaviour of reinforced plastic materials, when subject to thermal ageing, depends: a) on the material - chemistry of the fibre, interface and matrix product constituents; - fibrous structure of the material; - differences in physical and/o
11、r mechanical properties between the different component materials; - internal stresses induced during processing. b) on environmental conditions - temperature level; - pressure and oxygen content of the air; - radiation. c) on operating conditions (stress, environment, etc.) The effects of thermal a
12、geing on the laminate are: - change and/or deterioration in its physical appearance; - internal deterioration (cracking, delamination, etc.); - change in the amount of cross linkage, in the level of crystallinity followed by an irreversible deterioration in the matrix and/or interface; - variations
13、in mass; - changes in the different mechanical characteristics dependent on the matrix and/or the interface. The use of fibre reinforced plastic for applications in a hot atmosphere shall be qualified by: - ageing tests, which cover the intended range of operating conditions (.e., temperature and ti
14、me). Care shall be taken with any extrapolation of the data outside the qualified range; - measuring the properties most representative of those which will be experienced in the intended application. The main purpose of this test method is to allow a relative classification of the different material
15、s exposed in identical conditions to be produced. 1 Scope This standard defines a method of evaluating the influence of exposure to constant temperature, under dry atmospheric pressure conditions, and without mechanical loading, on the characteristic properties of fibre reinforced plastics for aeros
16、pace applications. This standard is applicable to all fibre reinforced materials, irrespective of the fibre or organic resin matrix, when specified by the technical specification or material standard. This specification shall be used only to compare the characteristics: - of a material at different
17、stages of exposure compared to this material in its initial state before exposure. - of different materials at the same state of exposure (same temperature and same ageing times). This specification will not allow the change in characteristics of a material in a real configuration to be predicted be
18、cause of the absence of any eventual interactions created by the environment mechanical loadings and the thermal cycles. Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMANot for ResaleNo reproduction or networking permitted without lic
19、ense from IHS-,-,-Page 4 prEN 4238: 1998 2 Normative references This 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 dated references, sub
20、sequent 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 2331 Aerospace series - Textile glass fibre preimpregnates - Tes
21、t method for the determination of the resin and fibre content and mass of fibre per unit area EN 2564 Aerospace series - Carbon fibre laminates - Determination of the fibre, resin and void contents 1) EN 2743 Aerospace series - Fibre reinforced plastics - Standard procedures for conditioning prior t
22、o testing 1 ) EN 2744 Aerospace series - Non metallic materials - Preferred test temperatures EN 3615 Aerospace series - Fibre reinforced plastics - Determination of the conditions of exposure to humid atmosphere and moisture absorption 3 Definitions For the purpose of this standard the following de
23、finitions apply: - Intermediate (semi-finished product): Supplied material constituted of products having been subjected to a partial process giving it, at delivery, a state different to that of final use (prepregged fabric, moulding compounds, etc). - Interface: In a laminate, the interface is the
24、contact surface between reinforcement and matrix. - Matrix: Material which links the reinforcements products (fibres, fabrics, etc) between them to form the composite laminate. - Component products (basic constituents, raw materials): Supplied material used for the manufacture of intermediates (resi
25、ns, hardeners, accelerators, solvents, additives, fibres, fabrics, etc.). - Initial state: State of the material prior to exposure. 4 Principle Test specimens or test samples are exposed for pre-determined periods, under controlled conditions protected from light, to a gentle regular dry air flow. T
26、he air, which is at atmospheric pressure, is held at the exposure temperature for defined time periods and is regularly renewed. At the end of each exposure period the most meaningful characteristics are measured and compared to those measured in the initial state. 1) Published as AECMA Prestandard
27、at the date of publication of this standard Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-STD-AECMA PREN Li238-ENGL L978 LOIIZIIII 0011i337 4TT Page
28、5 prEN4238: 1998 The exposure conditions are: - either, those defined in the technical specification and(or) the appropriate material standard; - or, where a material needs to be evaluated within a particular thermal range, those establised by means of preliminary tests to determine the reference te
29、mperature for the evaluation programme; for example, the reduction in a (or a number of) characteristic(s) of x % (25%, 40%, etc.) after 2 O00 h of exposure at the reference temperature. NOTE: The hygrometry of the air circulating in the oven is the natural hygrometry occuring in the surroundings. H
30、owever, particular hygrometric conditions, with a nitrogen/oxygen (altitude) and/or pressure ratio (altitude, engine environment, etc.) may be specified by a material standard or technical user specifications. The characteristics to be measured in order to assess the deterioration of the material sh
31、all normally correspond to those which best show this change, these are usually: - changes in physical appearance; - change in mass of the material; - reduction in mechanical characteristics linked to the plastic matrix material and(or) the fibre/matrix interface. NOTE: A comparison between differen
32、t matrices, according to this standard, is only possible if the samples are: - subjected to the same exposure conditions; - of the same geometry and surface state; - reinforced, with the same reinforcement (fibre, volume content, number of plies, structure of fibres within the ply, etc.). 5 Apparatu
33、s 5.1 Balance accurate to: - 0,l mg for a mass of test piece M 5 1 O g; - l O-4 M (sampling mass) if M 10 g. 5.2 5.3 Oven Magnifying glass with magnification 10 X An air circulating oven capable of achieving a regular and continuous change of air, and maintaining temperature uniformity within the sp
34、ecified limits for each specimen situated in the effective volume of the oven: - in use, the oven shall be protected from radiation, ie light, ultra-violet, infra red etc.; - the capacity of the oven shall be such that the total volume of test specimens/test samples for each test campaign does not e
35、xceed 2 % of the effective volume; - the oven shall be equipped with means of supporting or suspending the test specimensltest samples. A distance of 10 mm between test specimens/test samples and 50 mm between test specimens/tect samples and the oven wall shall be maintained; - the type of material
36、used to support the test specimendtest samples shall not influence the action of oxygen or humidity on the test specimens/test samples. The renewal of air in the oven shall range from 3 to 10 times the effective volume of the oven per hour in order to ensure a more or less constant oxygen content. T
37、he oven shall be equipped with an integrated and derivative proportional (IDP) temperature control system or equivalent. Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMANot for ResaleNo reproduction or networking permitted without lic
38、ense from IHS-,-,-Page 6 prEN 4238: 1998 - At the start of exposure: The oven shall be capable of a rise in temperature, when empty, of between 2 OC/min and 5 OC/min. The thermal controls shall be set such that during heat up overshooting of the exposure temperature does not occur. - A preliminary c
39、heck of the temperature uniformity within the oven shall be made using a dummy load, representative of the actual intended test specimens/test samples to be tested, to ensure that the temperature control probes and temperature monitoring probes are suitably positioned. - A temperature indicator with
40、 a minimum of six measurement channels shall be used for this check. - In stabilised mode, each test piece shall be maintained at the specified temperature within the tolerances given in EN 2744. - Continous monitoring of temperature as a function of time during exposure shall be made using a minimu
41、m of two recording channels, one monitoring the low temperature zone, and one monitoring the high temperature zone of the effective oven volume. If a continous recording equipment is not available, the oven shall be fitted with a device to determine: - the maximum temperature attained; - the instant
42、 that maximum temperature is attained should a fault occur during the exposure period. 5.4 Dessicator Dessicator containing a drying agent such as silica gel or phosphoric anhydride. For dessicator use conditions, see EN 361 5 (Method BI. 6 Test specimens and samples Exposure to dry heat may be carr
43、ied out using: - Test samples prior to machining of test specimens - option P. - Test specimens machined to final dimensions prior to exposure - option E Unless otherwise specified by the technical specification or material standard option E shall be used. 6.1 Material The process for manufacturing
44、the material for test samples or test specimens shall be as that specified in the material standards or that recommended by the prepreg manufacturer. In the case of an evaluation programme for a new unknown material, the ply orientation of the test panels shall whenever possible conform to the follo
45、wing criteria: - Mirror image symmetry of the plies (fibres orientation and position of fabric faces) with respect to the mid-plane of the lay-up. - Alternate crossing of plies (lamination most sensitive to the effects and action of oxygen). - Laminate thickness 1,5 mm to 3mm. The fibre content shal
46、l be in conformity with the material standard. The laminate faces are as-made, that is corresponding to those obtained after removal of the peel plies. 6.2 Test specimen The geometry of the test specimen shall conform to the requirements of the relevant test method. The number of test specimen shall
47、 conform to the requirements of the relevant technical specification or the material standard. Test specimen shall be in the as machined condition. Particular attention shall be paid to the condition of the edges of the test specimen, in particular over heating and delamination of the plies shall no
48、t be accepted. When tabs are required to be bonded to the test piece to enable testing to be carried out after exposure, these may be bonded to the test specimen after exposure, particularly where there is a risk of the bonded joint being degraded during exposure. Test specimen dimensions shall be m
49、easured prior to exposure. Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-STD-AECMA PREN Li238-ENGL 1998 LOL23LL OOL43LiL 058 Page 7 prEN4238: 1998 6.3 Marking Identification markings shall be in a area of the test specimen/sample which is not critical to the
