NF T25-714-2008 Advanced technical ceramics - Ceramic composites - Methods of test for reinforcement - Part 6 determination of tensile properties of filament at high temperature 《.pdf

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1、NF EN 1007-6February 2008Ce document est usage exclusif et non collectif des clients Saga Web.Toute mise en rseau, reproduction et rediffusion, sous quelque forme que ce soit,mme partielle, sont strictement interdites.This document is intended for the exclusive and non collective use of Saga Web cus

2、tomers.All network exploitation, reproduction and re-dissemination,even partial, whatever the form (hardcopy or other media), is strictly prohibited.Saga WebFor SHANGHAI INTERNAT SCIENCE any slippage in the load train as evidenced by a drop in the force/displacement curve, before reaching the maximu

3、m tensile force; any deviation from linearity in the load/cross-head displacement curve after the initial slack has been taken up. The following circumstance invalidates only the determination of the strength and strain to failure: failure outside the uniformly heated length Lh.7.2.7 Calculation of

4、results 7.2.7.1 Calculation of the hot zone compliance, ChThe load train compliance is determined at each test temperature. NOTE This is because some of the contribution to load train compliance can vary with temperature. Calculate the total compliance Ct for the tests at each fibre length Lf from t

5、he inverse slope in the linear part of the force/cross-head displacement curve. For each test, plot the total compliance Ct versus the fibre length. Perform a linear regression analysis of Ct versus the fibre length, and determine the heated zone compliance Ch from the intercept as shown on Figure A

6、.3. The load train compliance at room temperature Cl is determined in accordance with EN 1007-4, by using the same fibre length. 7.2.7.2 Strain of the specimen, Calculate the strain of the specimen from the following equation: 2hh 10LCF (4) where is the strain of the specimen, in %; F is the corresp

7、onding applied force, in Newtons (N); Ch is the hot zone compliance, in millimetres per Newton (mm.N-1);Lh is the uniformly heated length, in millimetres (mm). EN 1007-6:2007 (E) 177.2.7.3 Tensile strength Calculate the tensile strength from the following equation: 0mm AF (5) where m is the filament

8、 strength, in megapascals (MPa); Fm is the maximum load, in Newtons (N);A0 is the initial cross-sectional area, in square millimetres (mm2).7.2.7.4 Elastic modulus The elastic modulus is calculated from the following equation: 1010AFE (6)where E is the elastic modulus, in gigapascals (GPa); A0 is th

9、e initial cross-sectional area, in square millimetres (mm2);is the strain of the specimen, in %; F is the corresponding applied force, in Newtons (N). 7.2.7.5 Tensile strain at failure The tensile strain at failure, m is calculated from the following equation: E10mm (6) where m is the tensile strain

10、 at failure, in %; m is the tensile strength, in megapascals (MPa); E is the elastic modulus, in gigapascals (GPa). 7.2.8 Test report The report shall be in accordance with the reporting provisions of EN ISO/IEC 17025 and shall contain at least the following information: a) name and address of testi

11、ng establishment; b) date of test; EN 1007-6:2007 (E) 18c) on each page, a unique report identification and page number; d) customer name and address; e) reference to this standard, i.e. determined in accordance with EN 1007-6:2007; f) authorising signature; g) any deviation from the method describe

12、d, with appropriate validation, i.e. demonstrated to be acceptable to the parties involved; h) description of the equipment used; i) complete identification of the tested filament (manufacturer, type, batch, date of receipt, etc.); j) agreed sampling scheme for selecting test specimen from the batch

13、 of material; k) method employed for determination of the filament diameter, and average filament diameter; l) number of tests carried out and the number of valid results obtained; m) for each test specimen, the gauge length expressed in millimetres; n) heating rate, temperature of test and displace

14、ment rate; o) individual values of tensile strength and strain to failure, the average tensile strength and strain to failure, and the average elastic modulus; p) temperature profile of the furnace; q) values of the uniformly heated length Lh, the test specimens lengths L 1f , L 2f and L 3f ;r) deta

15、ils of any aspect of experimental procedure that might influence the results; s) comments on the test or test results. 7.3 Method B 7.3.1 Principle of the method The principle of this method is summarised in Annex B.7.3.2 Test specimens The test specimen length, Lf, shall be such as the room tempera

16、ture is reached at the ends. 7.3.3 Test specimen preparation Extreme care shall be taken during specimen preparation to ensure that the procedure is repeatable from specimen to specimen and to avoid handling damage. 7.3.4 Number of test specimens For each test condition at high temperature, five val

17、id test results at each of the three uniformly heated lengths, Lh,are required. NOTE 1 If a statistical evaluation is required, the number of test specimens at any of the above total lengths should be in accordance with EN 843-5. EN 1007-6:2007 (E) 19NOTE 2 A compliance determination is not required

18、, hence no more than one furnace, if only strength needs to be determined.7.3.5 Test procedure 7.3.5.1 Test set-up: determination of the temperature profile for each of the three furnaces and determination of the uniformly heated length, LhThe following determinations shall be carried out under actu

19、al test conditions. Prior to testing, the temperature profile inside the furnace shall be established over the temperature range of interest in order to determine the uniformly heated length, Lh, at each temperature of interest. This shall be done by measuring the temperature at least at 10 location

20、s distributed along the length of the empty furnace. The determination of the uniformly heated length, Lh, critically depends on the accuracy of the temperature profile. Also in this method A, the gauge length, L0, is equal to the uniformly heated length Lh.7.3.5.2 Test set-up: other considerations

21、- Determination of the cross-section area A0The filament diameter varies with temperature and the variation is very difficult to measure. The filament diameter and thus the cross-sectional area at test temperature shall be measured at room temperature in accordance with EN 1007-3. 7.3.6 Testing tech

22、nique 7.3.6.1 General Carry out the following in the order given. 7.3.6.2 Load cell Zero the load cell. 7.3.6.3 Specimen mounting Mount the specimen in the load train with its longitudinal axis coinciding with that of the test machine. Care shall be taken not to induce torsional loads or surface dam

23、age to the filament. Repeat this operation for each of the three lengths of furnace 7.3.6.4 Setting of the controlled atmosphere When testing under inert gas, air and water vapour shall be removed before setting the inert atmosphere. This can be done by establishing a vacuum (below 10 Pa) in the enc

24、losure, or by circulating inert gas. When testing under vacuum, the vacuum level shall be according to clause 5.4.3. NOTE In view of the extreme oxidation sensitivity of some of the filament material, conventional flushing of the test chamber might not be sufficient to reduce the oxygen level below

25、acceptable limits. 7.3.6.5 Heating of test specimen Raise the test specimen temperature to the required test temperature and maintain this test temperature for a short period to allow for temperature stabilisation. Ensure that the test specimen stays in the initial state of stress during heating. Th

26、e test specimen temperature is the furnace temperature. 7.3.6.6 Measurements Record temperature. EN 1007-6:2007 (E) 20Record vacuum or gas pressure if applicable. Set the cross-head speed. Record the force/cross-head displacement curve up to failure. Cool down until the risk of degradation is remove

27、d before opening the test chamber. 7.3.6.7 Test validity The following circumstances invalidate the test: failure to specify and record test conditions; any slippage in the load train as evidenced by a drop in the force/displacement curve, before reaching the maximum tensile force; any deviation fro

28、m linearity in the load/cross-head displacement curve after the initial slack has been taken up. The following circumstance invalidates only the determination of the strength and strain to failure: failure outside the uniformly heated length Lh.7.3.7 Calculation of results 7.3.7.1 Calculation of the

29、 hot zone compliance, Ch(Lh)Calculate the total compliance Ct for the tests at each of the heated zone length Lh.For each test, plot the total compliance Ct(Lh) versus the uniformly heated length Lh. Perform a linear regression analysis of Ct(Lh) versus the uniformly heated length, Lh, and determine

30、 the total compliance Ct(Lh 0) from the intercept as shown on Figure B.1. The load train compliance Cl is determined in accordance with EN 1007-4. Calculate the hot zone compliance Ch(Lh), from the following equation (see equation B.6): 0(RT)3hhththh10)0()()(AELLCLCLC (7) where Ch(Lh) is the hot zon

31、e compliance, in millimetres per Newton (mm.N-1);Ct(Lh) is the total compliance, in millimetres per Newton (mm.N-1);Ct(Lh 0) is the total compliance, when Lh approaches 0, in millimetres per Newton (mm.N-1);E(RT) is the Youngs modulus at room temperature determined in accordance with EN 1007-4, in g

32、igapascals (GPa); A0 is the initial cross-section area, in square millimetres, (mm2). EN 1007-6:2007 (E) 217.3.7.2 Strain of the specimen, Calculate the strain of the specimen from the following equation: 2hh 10LCF (8)where is the strain of the specimen, in %; F is the corresponding applied force, i

33、n Newtons (N); Ch is the hot zone compliance, in millimetres per Newton (mm. N-1);Lh is the uniformly heated length, in millimetres (mm). 7.3.7.3 Tensile strength Calculate the tensile strength from the following equation: 0mm AF (9) where m is the filament strength, in megapascals (MPa); Fm is the

34、maximum load, in Newtons (N);Ao is the initial cross-sectional area, in square millimetres (mm2).7.3.7.4 Elastic modulus The elastic modulus is calculated from the following equation: 1010AFE (10)where E is the elastic modulus, in gigapascals (GPa); Ao is the initial cross-sectional area, in square

35、millimetres (mm2);is the strain of the specimen, in %; F is the corresponding applied force, in Newtons (N). EN 1007-6:2007 (E) 227.3.7.5 Tensile strain at failure The tensile strain at failure, m, is calculated from the following equation: E10mm (11)where m is the tensile strain at failure, in %; m

36、 is the tensile strength, in megapascals (MPa); E is the elastic modulus in gigapascals (GPa). 7.3.8 Test report The report shall be in accordance with the reporting provisions of EN ISO/IEC 17025 and shall contain at least the following information: a) name and address of testing establishment; b)

37、date of test; c) on each page, a unique report identification and page number; d) customer name and address; e) reference to this standard, i.e. determined in accordance with EN 1007-6:2007; f) authorising signature; g) any deviation from the method described, with appropriate validation, i.e. demon

38、strated to be acceptable to the parties involved; h) description of the equipment used; i) complete identification of the tested filament (manufacturer, type, batch, date of receipt, etc.); j) agreed sampling scheme for selecting test specimen from the batch of material; k) method employed for deter

39、mination of the filament diameter, and average filament diameter; l) number of tests carried out and the number of valid results obtained; m) for each test specimen, the gauge length expressed in millimetres; n) heating rate, temperature of test and displacement rate; o) individual values of tensile

40、 strength and strain to failure, the average tensile strength and strain to failure, and the average elastic modulus; p) temperature profile of the furnace; q) values of the three uniformly heated lengths, Lh, temperature profile of each of the three furnaces and value of the fibre length Lf; EN 100

41、7-6:2007 (E) 23r) details of any aspect of experimental procedure which might influence the results; s) comments on the test or test results. EN 1007-6:2007 (E) 24Annex A(informative) Principle of method A The principle of method A is taken from 1. A schematic temperature distribution T = T(x) along

42、 the fibre in a high temperature cold end test is shown in Figure A.2. As E = E(T), the local strain changes along the specimen and one can distinguish three different zones: heated zone (h) along the furnace with practically isothermal conditions; gradient zone (d);room temperature zone (c) where t

43、he fibre is close to room temperature. Only the strain in the isothermal zone is relevant for the test result. To evaluate the true strain in the heated fibre zone of a high temperature cold end test, a modified compliance approach can be taken. The total compliance is composed out of the compliance

44、s of the different zones plus the load train contribution (l) of grip and machine respectively: Ct = Ch + Cd + Cc + ClFor Cl the value of the load train compliance obtained at room temperature can be used when the grips and machine are not influenced by the fibre heating, which can be assumed for co

45、ld end tests. In Figure A.1, the total compliance, Ct, is plotted for three tests on fibres of different length Lf. One can see that the total compliance rises with increasing specimen length. In a series of high temperature cold end tests, one changes the test specimen length, Lf, while keeping the

46、 length of the heated zone constant. This way, only Cc changes. Figure A.3 shows the result of the tests. Cl, Ch and Cd are assumed to remain constant during the test series. Their sum is found by extrapolating the total compliance to Lf (Lh+ 2 x Ld).If the length of the gradient zone, Ld, is small

47、compared with the length of the whole fibre, its contribution, Cd, can be neglected, and only the load train compliance found at room temperature is subtracted from the offset in order to find the compliance of the heated zone. The true strain of the specimen within the heated zone is then given by: hhLCF (A.1)