1、L - EUROPEAN STANDARD EN 2374 NORME EUROPEENNE EUROPAISCHE NORM April 1991 UDC: 678 067.5-41:620; 629.7 Descriptors: Aircraft industry, composite materials, reinforcing materials, laminates, laminated plates, glass cloth, manufacturing, characteristics, verification b English version Aerospace serie
2、s - Glass fibre reinforced mouldings and sandwich composites - Production of test panels Srie arospatiale - Matriaux Luft-und Raumfahrt - stratifies renforcs de fibres de verre Glasfaserverstarkte Formstoffe und et matriaux composites sandwich - Kernverbunde - Herstellen von Prparation des panneaux
3、dessais Prfplatten This European Standard nas approved by CEN on 1991-03-28 CEN members are bound to comply with the CENICENELEC 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 biblio
4、graphical references concerning such national standards may be obtained on application to the Central Secretariat 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
5、a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, FPance, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, S
6、pain, Sweden, Switzerland and United Kingdom. CEN European Committee :for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, 8-1050 Brussels (cl CEN $991 Copyright reserved to all CEN members t7cf. No. EN 2?174:1991 E CEN EN*E374 L
7、m 3404589 OOL4OLO O Page 2 EN 2374:1991 Contents list 1 2 References Scope and field of application 3 Type of fabrication 4 Equipment and apparatus 5 Tooling 6 7 8 Fabrication of laminate test panels Fabrication of sandwich composite test panels Fabrication of test panels for establishing the adhesi
8、ve properties 9 Sampling 10 Test report Foreword 3 3 3 4 4 6 13 15 16 16 This European Standard has been prepared by the European Association of Aerospace Manufacturers ( AEC MA). After inquiries and votm carried o-ut in accordance with the rules of this Association, this Standard has successively r
9、eceived the approval of the National Associations and the Official Services of the member countries of AECMA, prior to its presentation to CEN. According to the Common CEN/CENELEC Rules, the following countries are bound to implement this European Standard : Austria, Belgium, Denmark, Finland, Franc
10、e, Germany, Greece, Iceland, Ireland, Italy, Luxemburg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. Page 3 EN 2374:1991 I This standard describes the production of laminate and sandwich composite test panels from glass fibre fabric and resin mixes. Test specimens, w
11、hich are specified for the determination of the characteristics of the glass fibre reinforced mouldings, for the verification of the properties of their components or for the verification of the adhesive and sandwich composite properties, are taken from the test panel in accordance with the relevant
12、 test standard. This standard is not applicable to the production of test panels from unidirectional glass fibre fabric and resin mixes, Scope and field of applicafion 2 References EN 2090 EN 2334 EN 2514 EN 2743 Aerospace series - Aluminium alloy 2024-T3 - Clad sheets and strips - 0,4- a G 6 mm 1)
13、Aerospace series - Pickling of aluminium alloys in chromic acid 2) Aerospace series -Aluminium alloy 5052-H191 - Honeycomb core 2) Aerospace series - Glass reinforced plastics - Standard atmospheres for conditioning and testing 2). 3 Type of fabrication 3.1 TypeA Glass fibre fabric is impregnated wi
14、th liquid resin mix and made into test panels in a press mould under the influence of pressure and temperature in accordance with the resin manufacturers processing instructions. 3.2 Type B Preimpregnated glass fibre fabric (prepreg) is made into test panels under the influence of pressure and tempe
15、rature in accordance with the manufacturers processing instructions. 3.3 TypeC Glass fibre fabric is impregnated with liquid resin mix and made into test panels at room or elevated temperature without application of pressure in accordance with the resin manufacturers processing instructions. 1) Publ
16、ished as AECMA standard at the date of publication of the present standard. 2) In preparation at the date of publication of the present standard. F 7 p_p- - 1 Page 4 EN 2374:1991 4 Equipment and apparatus For types A and B, a hydraulic or mechanical press, an autoclave or equipment for vacuum bag fa
17、brication is required. The equipment shall be fitted with a continuously variable temperature and pressure control, which allows the prescribed values to be kept constant over the entire cure time. Provided there are no other agreements with the material supplier, the equipment shall be suitable for
18、 maintaining the temperature with an accuracyof i 50C and the press pressure with an accuracyof f 5 %. When a press is used, it shall be ensured that the press mould described in clause 5 can be accommodated and that the closure rate for the last two millimetres of the closure travel does not exceed
19、 5 mm/min. The equipment shall be fitted with suitable measuring devices for monitoring the fabrication parameters temperature, time and pressure. In autoclave or vacuum bag fabrication, a vacuum indicator shall also be available. In vacuum bag fabrication, it shall be ensured that the vacuum pump c
20、an maintain a reduced pressure of at least 70 kPa in the bag during the entire cure time, Provided there are no different agreements with the material supplier, the production of the test panels is to be carried out in a light, well ventilated room at 15 OC to 30 OC and a relative humidity of 30 % t
21、o 75 %. 5 Tooling 5.1 Press moulds Press moulds according to figures and 2 are usedfor the production of test panels in a press. The choice of the press mould is to be made according to the material to be processed and the purpose of the test. The press moulds shall satisfy the following requirement
22、s : a) length and breadth of the pressing areas of the press mould shall be large enough to allow the manufacture of test panels from 150 mm X 150 mm to 400 mm X 400 mm. b) the moulding surfaces (surfaces designed for shaping the test paneis) of the press mould should be hardened, polished and, if p
23、ossible, hard chromium plated. c) the lower moulding surface shall have a mark, which is reproduced on the test panel on pressing, in order to make the lower side of the test panel identifiable after the pressing procedure. The mark on the test panel shall not have a deleterious effect on the subseq
24、uent tests (see first note page 6). d) the temperature over the entire moulding surface of the press mould shall not deviate locally by more than zk 3 OC from the specified value e.g. measured by means of a thermocouple. 7 - i CEN EN*Z374 71 I- 3404587 0014013 b Page 5 EN 2374:1991 - e) the press mo
25、uld type 1 consists of the elements shown in figure 1. The height of the frame shall be large enough to provide a moulding cavity in which the glass fibre fabric impregnated with the resin mix can be inserted in one operation. r Upper die I l Dowel Frame Lower die Figure 1 - Press mould type 1 f) th
26、e mould type 2 consists of the elements shown in figure 2. The plates shall be plane and parallel and are guided only at the four corners (open press mould). By placing spacers in the region of the guides, it is possible to mould to stops if required, .e. a specific thickness of the test panel can b
27、e set. Spacers of variable thickness Figure 2 - Press mould type 2 CEN ENx2374 91 E 3404589 OOL4014 8 E Page 6 EN 2374:1991 NOTE : The properties of the upper and lower faces of a pressed test panel are not exactly the same. As a result of the time span, which is necessary for putting the laminate i
28、n place and the closure process, the lower face of the test panel is heated longer and possibly also subjected to a higher temperature than the upper face. In the standards concerned, therefore, it is to be stipulated, if necessary, for which surface of the test panels the results shall be valid. 5.
29、2 Tools for autoclave and vacuum bag fabrication For the fabrication of the laminate test panels, a pressure-tight base plate for the assembly, cover plate and various ancillaries, such as release films, sealing tape etc., are needed. For the fabrication of sandwich composite test panels, a rigid fr
30、ame is also required, which shall be adjusted so that it takes up the forces acting laterally on the sandwich composite structure in this fabrication process. 5.3 Tools for hand lay-up of laminate For the production of test panels in accordance with method C, a plane fixed support, approx. 500 mm X
31、500 mm in size and a cover (e.9. of glass) of the same size, are required, as well as spacers which can be inserted between the support and cover plate, NOTE : Air bubbles can be detected easily if the support is either darkcoloured or translucent and illuminated from below. 6 6,1 Preparation Fabric
32、ation of laminate test panels 6.1.1 Pretreatment Unless otherwise specified, a pretreatment of the semifinished products shall be carried out for at least 2 h in the standard atmosphere in accordance with EN 2743. 6.1.1 -1 Glass fibre fabric A sufficient number of plies of glass fibre fabric for the
33、 fabrication of the test panel, see clause 6.1.2, is cut to size and dried in air for 1 h at 80%. Then the plies are immediately stacked flat upon one another in a desiccator, where they shall be allowed to cool to room temperature. The drying can be omitted if the glass fibre fabric plies are kept
34、in the standard atmosphere in accordance with EN 2743, for at least 48 h before processing. 6.1 .I .2 Preimpregnated glass fibre fabric Preimpregnated glass fibre fabric products, which have to be stored at tempe ature lo! th le Dtn temperature, shall be air-tight packed then be broughtto room tempe
35、rature in a polyethylene bag so that no moisture pick-up can take place. The time required for the equilibration of temperature depends on the amount, but it shall not be less than 4 h. The time required is to be stated in the report. CEN EN82374 91 m 3404589 OOL4OL5 T m Page 7 EN 2374:1991 6.1.2 Th
36、e number of plies of glass fibre fabric needed for a specific laminate thickness and a specific glass content can be calculated according to the following formula : Number of plies of glass fibre fabric for types A and C in which ; n GL - PGL = PRM = b= - - S - number of plies of glass fibre fabric
37、thickness of the test laminate, in mm mass per unit area of the glass fibre fabric product, in g/m* density of the glass fibre fabric product, in g/cm3 density of the resin mix, in g/cmJ glass content of the test laminate, in mass-%. The number of plies of glass fibre fabric determined by this formu
38、la is to be rounded up or down in such a way that the test panel complies with the glass content in accordance with subclause 6.1.5 and also the thickness requirement specified in the test standard. - - - .-._ _ - _ - . . ._ . _ ._ - -. -. . . 6.1.3 Resin mixes 6.1 3.1 processing instructions. The r
39、esin mixes shall be produced and processed in accordance with the resin manufacturers 6.1.3.2 following formula ; The amount mRM of the resin mix theoretically required is calculated according to the 100 - b b RM = mtot. . in which : mtot. = b = glass content in mass-%. The theoretically determined
40、amount mRM is to be increased by a least 20 % for the laminating process in practice to ensure a sufficient resine flow. mass of all plies of glass fibre fabric, in g 6.1.4 - fhmber of plies of preimpregnated glass fibre fabric for type B The number of plies of glass fibre fabric necessary for a spe
41、cific laminate thickness and a specific glass content can be calculated according to the formula given in subclause 6.1.2. For a sufficient resin flow, the glass content of the prepreg minus 1 % is used for b (glass content in mass-%) in the formula. CEN EN*2374 91 m 3404589 OOI4OLb I Page 8 EN 2374
42、:1991 6.1.5 Glass content of the test panels The glass content of the panels expressed in volume-% or mass-% shall comply with the appropriate material standard. Data for the glass content shall be given in volume-% particularly if test panels are made for comparison of different fibre-reinforced mo
43、uldings. The conversion of the glass content from volume-% to mass-% can be carried out according to the following formula : PGL PL b=bv. - avec : b“ PL = 100 GL - PRMI + PRM in which : b = glass content of the test panels in mass-% bv = glass content of the test panels in volume-% PGL = p = density
44、 of the test panel in g/cmJ PRM = density of the resin mix in g/cm3. density of the glass fibre fabric product in g/cm3 For information, the relationship between b, and b for a density of the glass fibre fabric product of PGL = 2,53 g/cma and a density of the resin mixPRM = 1,20 g/cm3 or 1,30 g/cmU,
45、 respectively can be inferred from figure 3. I ! I I i I 1 I I ! -I 7 I. b“ 96 50 40 30 I l 1 I 60 70 b% 50 Figure 3 - Relationship between the glass content bv (volume-%) and the glass content b (mass-%) i - -7 ICEN EN*k2374 91 I 3404589 0014017 3 I 1 Page 9 EN 2374:1991 6.1.6 Cutting the glass fib
46、re fabric to size For type A, the glass fibre fabric is cut into pieces, which are 3 mm to 6 mm shorter than the length and breadth of the pressing area of the lower die with press mould type 1 or at least 10 mm shorter than the length and breadth of the pressing area with press mould type 2. For ty
47、pe C, the glass fibre fabric is cut into pieces of at least 400 mm X 400 mm. Woven glass fibre fabric is divided up and cut to size into the pieces required, after previously marking 2 cm deep cuts at the edges with shears. Coarse woven fabric can be cut along one thread, fine woven fabric only afte
48、r pulling out one thread. At the cut edges, some fibres are frayed, so that, when the laminate is formed, these fibres do not impair the operation by falling out. At each cut, care must be taken to ensure that a distinction between the warp and weft directions is possible; this is achieved e.g. by r
49、ectangular cuts. 6,1.7 For type B, the prepreg is cut into pieces, which are 3 mm to 6 mm shorter than the length and breadth of the pressing area of the lower die with press mould type 1 or at least 10 mm shorter than the length and breadth of the pressing area with press mould type 2. Cutting preimpregnated glass fibre fabrics to site 6,1.8 Release agents Release agents areto be chosen in such way that they do not affect the properties of the test panels and are easy to remove. This is particularly important if electrical properties an
