Detail of GB/T 41762.2-2022

Introduction of GB/T 41762.2-2022

1 Scope This document describes a bending test method for determining the tensile strength, tensile breaking strain and tensile modulus of carbon fibre reinforced plastic composite (CFRP) laminates in the thickness direction (out-of-plane). This document is applicable to unidirectional carbon fibre reinforced plastic composite (UD-CFRP) laminates. In addition, the calculation of the effective volume is described due to the dimensional effect of the tensile strength in the thickness direction. 2 Normative references The contents of the following documents constitute essential provisions of this paper by means of normative references in the text. Where a reference is dated, only the version corresponding to that date applies to this document; where a reference is not dated, the latest version (including all amendment sheets) applies to this document. ISO 291 Plastics - Standard atmospheres for conditioning and testing Note: GB/T 2918-2018 Specification of Plastic Specimen Status and Standard Environment for Testing (ISO 291:2008, MOD) ISO 1268-1 Fibre reinforced plastics - Methods of producing test plates - Part 1: General conditions Note: GB/T 27797.1-2011 Fibre reinforced plastics, test panel preparation method Part 1: General (ISO 1268-1:2001, IDT) ISO 1268-4 Fibre reinforced plastics - Methods of producing test plates - Part 4: Moulding of prepregs Note: GB/T 27797.4-2013 Preparation of Fiber Reinforced Plastics Test Panels Part 4: Prepreg Molding (ISO 1268-4:2005, IDT) ISO 2818 Plastics - Preparation of test specifications by machining ISO 5893 Rubber and plastics test equipment - Tensile, flexural and compression types (constant rate of travel) - Specification Note: GB/T 17200-2008 Technical Specification for Rubber and Plastic Tensile Pressure and Bending Tester (Constant Speed Drive) (ISO 5893:2002, IDT) Weibull statistics for strength data of ISO 20,501 Fine ceramics (advanced ceramics, vanced technical ceramics) Note: GB/T 40,005 2021 Weibull Statistical Analysis Method for Strength Data of Fine Ceramics (ISO 205,012,019, MOD) 3 Terminology and definitions The following terms and definitions apply to this document. 4 Principle The specimen is rectangular and its length is oriented in the direction of the thickness of the CFRP laminate. The specimen is placed between two supports and the load is applied at a constant rate in the middle of the specimen until damage occurs on the outer surface of the specimen. The thickness direction properties are determined by the tensile stresses and strains generated in the specimen during the bending test. As strength is dependent on dimensional effects, quantitative estimates of dimensional effects should be made from tensile strength and effective volume. 5 Conditioning 5.1 Conditioning of the specimen If specified in the material specification, condition the specimen as specified; if not, choose the most suitable conditions in ISO 291 for conditioning the specimen, unless otherwise specified by the relevant party (e.g. testing at high or low temperatures). Preference shall be given to the standard environmental conditions of ISO 291 (23 °C and 50% relative humidity) for conditioning of the specimen, and humidity control is not necessary when the bending properties of the material are not sensitive to humidity. 5.2 test temperature and humidity Shall be tested in accordance with the conditions specified in 5.1. 6 instrumentation 6.1 Testing machine The test machine shall comply with ISO 5893 and 6.1 and 6.2 provisions. The test intensity wet rate shall be maintained constant in accordance with ISO 5893. 6.2 Load and deflection indicating device There shall be a load indicating device and the error in the indicated value of the load shall be less than 0.1 N. 6.3 Test fixtures 6.3 Test fixtures The positions of the two supports and the central loading indenter are shown in Figure 1. The radii of the corners of the supports and the loading indenter shall be 2 mm ± 0.2 mm and 5 mm ± o.2 mm respectively (see ISO 14125). 6.4 Deflection measurement system The displacement transducer shall be valid over the entire measurement range of the deflection. Making the original displacement transducer shall be agreed between the parties involved. the force required to operate the displacement transducer shall not exceed 1% of the breaking load of the specimen. 6.5 Data acquisition system It shall be possible to record bending load and deflection data. 6.6 Dimensional measuring instruments A micrometer with an accuracy of at least 0.005 mm or a dimensional measuring instrument of similar accuracy for measuring the width (b) and thickness (t) of the specimen. 7 Specimens 7.1 Shape and dimensions The shape and dimensions of the specimen shall conform to the provisions of Table 1. 7.2 Specimen preparation 7.2.1 General rules Test plates shall be prepared in accordance with ISO 1268-1 and ISO 1268-4 or other specifications/agreements. The specimen shall be prepared from the test plate by machining in accordance with ISO 2818 and shall be machined correctly to prevent damage to the specimen. 7.2.2 Test plates The UD-CFRP test plate is shown in the drawing. The in-plane fibre direction, the vertical in-plane fibre direction and the thickness direction are defined as direction 1, direction 2 and direction 3 respectively. 7.3 Specimen inspection The specimen shall be free from distortion, perpendicular to each other between adjacent planes, and free from pits, scratches, pockmarks and burrs on the surface and edges. When inspecting the specimen, the specimen should be pressed against a straightedge, right-angle ruler or flat plate, and the specimen should be visually observed or measured and checked with a micrometer. If the specimen does not meet the requirements, it should be discarded. 7.4 Number of specimens A minimum of 5 specimens should be tested if no estimation of effective volume and Weibull modulus is required. If an estimate of the effective volume and Weibull modulus is required, a minimum of 30 specimens should be tested. 8 Test procedure 8.1 Measure the width (b) and thickness (t) of the specimen to an accuracy of 0.005 mm. 8.2 Place the test fixture and adjust the span. The span should be greater than 25 times the thickness of the specimen. 8.3 The test rate is calculated according to equation (1): 8.4 The specimen is placed centrally on the support. 8.5 The load and displacement are recorded continuously throughout the test. 8.6 If required, the position of the damage is measured with a ruler or caliper. Damage patterns occurring in the vicinity of the loaded indenter area are considered acceptable, see Figure 3. 9 Calculations 9.1 Tensile stress in the thickness direction 9.2 Tensile strength in the thickness direction The thickness direction tensile strength is calculated according to equation (3): 9.3 Weibull modulus for bending tests The Weibull modulus is estimated by the bending test according to the procedure specified in ISO 20501. 9.4 Effective volume of the bending specimen The effective volume of the bending specimen is calculated in accordance with equation (4): 9.5 Tensile strain in the thickness direction The tensile strain in the thickness direction is calculated according to equation (5): 10 Precision Details of the inter-laboratory tests carried out to validate this test method and the precision data obtained from the tests are given in Appendix A. 11 Test report The test report shall contain the following: a) Name and number of this document b) the method of loading (bending method); c) full identification of the material tested, including type, material composition, source and manufacturer's information, etc; d) the method of preparation of the specimen and any details thereof e) the method of mechanical processing f) the number of specimens g) the size of the specimen h) the temperature, humidity and duration of the condition of the specimen; i) the temperature and humidity of the test j) Details of the test machine and displacement transducer k) span distance; l) Span-thickness ratio (L/t) for the bending test; m) test rate n) average value of tensile strength in the thickness direction, with standard deviation and 95% confidence interval of the average value, if required; o) mean value of the tensile modulus in the thickness direction, with standard deviation and 95% confidence interval of the mean value if required; p) the mean of the tensile breaking strain in the thickness direction, giving the standard deviation and 95% confidence interval of the mean, if required; q) load displacement curve and stress-strain curve r) if required, the location of the damage s) Weibull modulus, if required; t) effective volume, if required; u) date of test v) any operation not in accordance with this document and any event that may affect the test results. Appendix A (informative) Precision data obtained from inter-laboratory tests References

Contents of GB/T 41762.2-2022

1 Scope 2 Normative references 3 Terminology and definitions 4 Principle 5 Conditioning 6 instrumentation 7 Specimens 8 Test procedure 9 Calculations 10 Precision 11 Test report Appendix A (informative) Precision data obtained from inter-laboratory tests References