GB/T 38534-2020 English PDFUS$189.00 · In stock
Delivery: <= 3 days. True-PDF full-copy in English will be manually translated and delivered via email. GB/T 38534-2020: Test method for tensile properties of oriented fibre reinforced polymer matrix composite materials at ultra-low temperature Status: Valid
Basic dataStandard ID: GB/T 38534-2020 (GB/T38534-2020)Description (Translated English): Test method for tensile properties of oriented fibre reinforced polymer matrix composite materials at ultra-low temperature Sector / Industry: National Standard (Recommended) Classification of Chinese Standard: Q23 Classification of International Standard: 83.120 Word Count Estimation: 10,166 Date of Issue: 2020-03-06 Date of Implementation: 2021-02-01 Issuing agency(ies): State Administration for Market Regulation, China National Standardization Administration GB/T 38534-2020: Test method for tensile properties of oriented fibre reinforced polymer matrix composite materials at ultra-low temperature---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order. Test method for tensile properties of oriented fibre reinforced polymer matrix composite materials at ultra-low temperature ICS 83.120 Q23 National Standards of People's Republic of China Oriented fiber reinforced polymer matrix composite Ultra-low temperature tensile performance test method 2020-03-06 released 2021-02-01 implementation State Administration for Market Regulation Issued by the National Standardization Management Committee ForewordThis standard was drafted in accordance with the rules given in GB/T 1.1-2009. This standard was proposed by the China Building Materials Federation. This standard is under the jurisdiction of the National Fiber Reinforced Plastics Standardization Technical Committee (SAC/TC39). This standard was drafted. Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing FRP Research and Design Institute Co., Ltd. The main drafters of this standard. Qu Chengbing, Xiao Hongmei, Liu Yu, Fu Shaoyun, Wang Zhandong. Oriented fiber reinforced polymer matrix composite Ultra-low temperature tensile performance test method1 ScopeThis standard specifies the test equipment, samples, and sample shapes for the ultra-low temperature tensile performance test methods of oriented fiber reinforced polymer matrix composites. State adjustment, test procedures, calculations and test reports. This standard is applicable to the determination of continuous fiber (including fabric) reinforced polymer matrix composites at a temperature in the range of -196℃~-269℃ The in-plane tensile strength, tensile modulus of elasticity, Poisson’s ratio, and tensile failure strain of the material laminate.2 Normative referencesThe following documents are indispensable for the application of this document. For dated reference documents, only the dated version applies to this article Pieces. For undated references, the latest version (including all amendments) applies to this document. GB/T 1446 General Principles of Test Methods for Performance of Fiber Reinforced Plastics GB/T 3354 Test method for tensile properties of oriented fiber reinforced polymer matrix composites3 Principles of the methodUnder the environment of -196℃~-269℃, the long and straight thin plate sample is clamped by the clamping end and loaded with frictional force. Form a uniform tensile field, test the tensile strength, tensile modulus of elasticity, Poisson's ratio, and tensile failure strain of the material.4 Test equipment4.1 Testing machine The testing machine should meet the requirements of GB/T 1446. 4.2 Fixtures, tie rods, cryostat frame Materials with high strength, good toughness and low thermal conductivity should be used to make fixtures, tie rods, and cryostat frames, such as austenitic stainless steel Steel, martensitic steel, forged nickel-based superalloy and titanium alloy, etc. 4.3 Cooling device 4.3.1 Basic requirements The cooling device should be able to cool the sample to the specified temperature. The specified temperature is obtained by cooling with a cooling medium (such as liquid helium, etc.) or a refrigeration device (such as Refrigerator) is obtained by cooling. 4.3.2 Ultra-low temperature thermostat 4.3.2.1 The frame of the cryostat should match the testing machine and can accommodate the cryostat. 4.3.2.2 The ultra-low temperature thermostat should use a stainless steel vacuum Dewar with a multi-layer insulation structure, and can ensure the temperature deviation of the test area Does not exceed ±3°C. The length of the isothermal zone should not be less than the length of the parallel section between the clamping ends of the specimen. 4.3.2.3 The cryostat shall not affect the coaxiality between the tensile force and the geometric axis of the specimen. 4.3.3 Auxiliary equipment The cryostat and the cooling medium infusion pipe should be vacuum insulated. If a cooling medium is used for cooling, it should be equipped with a cooling medium infusion pipe, Auxiliary equipment such as vacuum pumps, cooling medium Dewar flasks, nitrogen cylinders, etc.; if a refrigerator is used for cooling, auxiliary equipment such as circulating cooling water should be equipped. Note. When operating the cooling medium, the test personnel shall take safety precautions in accordance with relevant regulations in advance to avoid personal injury and damage to the test equipment and test equipment. Kind of damage. 4.4 Temperature measuring instrument The temperature measuring instrument consists of a thermometer and an indicating device. Its resolution should be equal to or better than 1℃, and the thermometer should cover the working temperature range And periodically calibrate. 4.5 Low temperature strain measuring device 4.5.1 Use extensometers or other low temperature strain measuring devices that can be used in low temperature environments to measure strain, and the measurement accuracy should meet Requirements of GB/T 1446. 4.5.2 The extensometer should be calibrated regularly under room temperature and actual test temperature. Refer to Appendix A for the calibration of extensometer at low temperature. 4.5.3 When using strain gauges at low temperatures, the adhesive pasting the strain gauges should match the strain gauges and specimens.5 Sample5.1 Shape and size The sample shape is shown in Figure 1, and the sample size is shown in Table 1.6 Sample state adjustmentBefore the test, the sample is placed in a laboratory at a temperature of 23 ℃ ± 2 ℃ and a relative humidity of 50% ± 10% for at least 24h.7 Test procedure7.1 Preparation before test Check the appearance of the sample according to GB/T 1446, and number the sample. Measure and record the width of 3 different sections of the sample working section Take the arithmetic mean of the degree and thickness, respectively, and measure the accuracy to 0.01mm. 7.2 Sample installation 7.2.1 When installing the sample in the cryostat, the signal wire of the instrument should be sufficiently loose. 7.2.2 The center line of the specimen shall be consistent with the center line of the fixture and the center line of the connecting rod. 7.2.3 After the installation of the sample is completed, the sample should be pre-loaded, and always keep the pre-load not exceeding 5% of the maximum breaking load. 7.3 Installation of temperature measuring device 7.3.1 When a gaseous cooling medium or refrigerator is used for cooling, a temperature measuring point should be installed at both ends and the middle of the sample working section, and Keep the temperature measuring head in good contact with the sample surface. 7.3.2 When the liquid cooling medium is used for cooling, the sample is completely immersed in the cooling medium, and the temperature can be measured at any point in it. 7.4 Installation of low temperature strain measuring device 7.4.1 When measuring strain with one or more extensometers, install the extensometers as far as possible in the middle of the length of the specimen working section. 7.4.2 When using strain gauges to measure tensile strain, the temperature compensation sheet method shall be used for measurement. Note. The temperature compensation sheet method is to attach the resistance strain gauge to a piece of material that is the same material as the sample but does not participate in the deformation, and is at the same temperature bar as the sample Pieces. Correctly connect the compensation sheet to the Wheatstone bridge circuit to eliminate the influence of temperature changes. 7.5 Cooling process 7.5.1 Before cooling, use an air jet or hot blower to thoroughly dry the cryostat. 7.5.2 Install a cryostat to cool the sample. a) When a cooling medium with a boiling point lower than liquid nitrogen is used for cooling, the ultra-low temperature thermostat should be vacuumed first (the relative vacuum degree should be less than -0.097MPa), then use liquid nitrogen to pre-cool it, then empty the liquid nitrogen, and finally enter the low boiling point into the ultra-low temperature thermostat Cooling medium for liquid nitrogen; b) When the refrigerator is used for cooling, the ultra-low temperature thermostat should be kept in a vacuum state (the relative vacuum degree should be less than -0.097MPa) until the test The test is over. 7.5.3 After the sample is cooled to the specified test temperature, it should be kept for a certain period of time. a) When the cooling medium is liquid, the holding time is not less than 10 minutes; b) When the cooling medium is gaseous, the holding time is not less than 20min; c) When the refrigerator is cooling, the holding time is not less than 30min. 7.5.4 When the cooling medium is gaseous or refrigerating, it is allowed to be between the specified test temperature value and the measured temperature display value at the middle position of the sample The temperature deviation does not exceed ±2℃. During the test, the absolute value of the temperature difference between the two ends of the working section of the sample should not exceed 3°C. 7.5.5 When the test temperature is -196℃ or -269℃, the whole sample can be immersed in liquid nitrogen (-196℃) or liquid helium (-269℃) to cool However, obtain the required test temperature. 7.6 Loading 7.6.1 When the sample reaches the test temperature, zero the extensometer or strain gauge. When the extensometer or strain gauge is stable, the speed is 1mm/min~ Load continuously at a loading speed of 2mm/min until the specimen is broken, and record the load-strain (or load-displacement) curve and maximum load of the specimen. Load, failure load and failure strain or strain that may be close to the instant of failure. 7.6.2 The failure mode description after the sample is destroyed, according to the provisions of GB/T 3354.If the specimen is damaged in the clamp or at the end, it shall be invalidated.8 Calculation8.1 Tensile strength The tensile strength is calculated according to formula (1), and the result retains 3 significant figures. σt= Pmax Wh (1) Where. σt --- Tensile strength, in megapascals (MPa); Pmax---the maximum load that the sample bears before failure, in Newton (N); W --- sample width, in millimeters (mm); h ---The thickness of the sample, in millimeters (mm). 8.2 Tensile modulus of elasticity The tensile modulus of 90° sample is calculated according to formula (2) or formula (3) within the longitudinal strain range of 0.0005 to 0.0015, and the tensile elasticity of other samples The modulus is calculated according to formula (2) or formula (3) within the range of 0.001 to 0.003 longitudinal strain, and the result retains 3 significant digits. Et= ΔPl WhΔl (2) Et= Δσ Δε (3) Where. Et --- Tensile modulus of elasticity, in megapascals (MPa); l --- The gauge length of the extensometer in the working section of the sample, in millimeters (mm); ΔP --- load increment, in Newton (N); Δl ---The deformation increment within the gauge length of the extensometer corresponding to ΔP, in millimeters (mm); Δσ ---The increase in tensile stress corresponding to ΔP, in megapascals (MPa); Δε ---Strain increment corresponding to ΔP, dimensionless. 8.3 Poisson's ratio Poisson's ratio is calculated according to formula (4) within the same strain range as the tensile elastic modulus, and the result retains 3 significant figures. μ12= Δε horizontal Δε vertical (4) ε vertical = ΔlL lL (5) εHorizontal= ΔlT lT (6) Where. μ12 ---Poisson's ratio; Δεlongitudinal --- the longitudinal strain increment corresponding to the load increment ΔP, see formula (5), dimensionless; ΔεHorizontal --- the transverse strain increment corresponding to the load increment ΔP, see formula (6), dimensionless; lL --- the gauge length of the longitudinal extensometer, in millimeters (mm); lT --- the gauge length of the transverse extensometer, in millimeters (mm); ΔlL---corresponding to the longitudinal deformation increment of ΔP, in millimeters (mm); ΔlT---corresponds to ΔP lateral deformation increment, the unit is millimeter (mm). 8.4 Tensile failure strain The longitudinal tensile failure strain measured by the extensometer is calculated according to formula (7), and the result retains 3 significant figures. εlt= Δlb (7) Where. εlt ---longitudinal tensile failure strain, dimensionless; Δlb --- the longitudinal deformation within the gauge length of the extensometer when the sample is broken, in millimeters (mm). 8.5 Test results For each set of tests, calculate the arithmetic mean, standard deviation and dispersion coefficient of each measurement performance in accordance with the provisions of GB/T 1446.9 Test reportThe sample report generally includes all or part of the following. a) The name and implementation standard of the test item; b) Test personnel, test time and location; c) The source and preparation of the sample, material variety and specifications; d) The layering form, number, shape and size, appearance quality and quantity of the sample; e) Test temperature, relative humidity of the laboratory; f) The cooling method and cooling time of the sample; g) Test rate and method of measuring strain; h) The model of the test instrument; i) The failure mode of the specimen; j) Test results.Appendix A(Informative appendix) Calibration of extensometer at low temperature A.1 The calibration of the extensometer at low temperature should be calibrated with a calibrator, and the calibration coefficient should be obtained. The calibrator should have a length measuring device (such as One end is equipped with a micrometer with a certain length of casing combination structure, the inner layer is a vertical telescopic tube, and the outer layer is a fixed casing), and the allowable error should not be large At 1/3 of the allowable error of the extensometer, the minimum graduation value of the calibrator micrometer should not be greater than 0.001mm. A.2 Install the two blades of the extensometer on the vertical telescopic tube and the fixed sleeve of the calibrator according to the specified gauge length, and then place this end In the actual test temperature environment. A.3 The lead wire of the extensometer is connected to the strain gauge in the prescribed manner, and then the working state of the strain gauge is adjusted to be the same as the sample in the actual test. The state when loaded with temperature is the same. A.4 Rotate the micrometer of the calibrator and apply a positioning shift to the extensometer through the vertical telescopic tube, and read and give the positioning phase shift from the strain gauge For the corresponding strain of the extensometer, determine the calibration coefficient of the extensometer according to formula (A.1). K= Δl l0·ε meter (A.1) Where. K --- calibration coefficient of extensometer; Δl --- the positioning shift of the micrometer, the unit is millimeter (mm); l0 --- The specified gauge length of the extensometer, in millimeters (mm); ε meter---extensometer strain. A.5 Calibration should be carried out in two sets of tests, and the method of applying displacements in grades shall be adopted. Evenly distributed in the entire calibration range of the extensometer. 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