Fibre-reinforced plastic composites—Determination of laminate through-thickness properties—Part 2:Determination of the elastic modulus,the strength and the Weibull size effects by flexural test of unidirectional laminate,for carbon-fibre based systems
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
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
1范围
本文件描述了测定碳纤维增强塑料复合材料(CFRP)层合板的厚度方向(面外)拉伸强度、拉伸破坏应变和拉伸模量的弯曲试验方法。
本文件适用于碳纤维增强塑料复合材料单向(UD-CFRP)层合板。此外,由于厚度方向拉伸强度存在尺寸效应,还描述了有效体积的计算。
2规范性引用文件
下列文件中的内容通过文中的规范性引用而构成本文作必不可少的条款。其中,注日期的引用文件,仅该日期对应的版本适用于本文件;不注日期的引用文件,其最新版本(包括所有的修改单)适用于本文件。
ISO 291塑料试样状态调节和试验的标准环境(Plastics - Standard atmospheres for conditioning and testing)
注:GB/T 2918-2018塑料试样状态得书和试验的标准环境(ISO 291:2008,MOD)
ISO 1268-1纤维增强塑料试验板制备方法第1部分:通则(Fibre-reinforced plastics - Methods of producing test plates - Part 1:General conditions)
注:GB/T 27797.1-2011纤维增强塑料﹑试验板制备方法第1部分:通则(ISO 1268-1:2001,IDT)
ISO 1268-4纤维增强塑料试验板制备方法第4部分:预浸料模塑(Fibre-reinforcedplastics - Methods of producing test plates - Part 4:Moulding of prepregs)
注:GB/T 27797.4-2013 纤维增强塑料试验板制备方法第4部分:预浸料模塑(ISO 1268-4:2005,IDT)
ISO 2818塑料机械加工制备试样(Plastics - Preparation of test specimens by machining)
ISO 5893橡胶和塑料试验设备拉伸弯曲和压缩型(恒速驱动）规范[Rubber and plasticstest equipment - Tensile，flexural and compression types(constant rate of traverse) - Specification]
注:GB/T 17200-2008 橡胶塑料拉力压力和弯曲试验机(恒速驱动）技术规范(ISO 5893:2002,IDT)
ISO 20501精细陶瓷(先进陶瓷先进技术陶瓷)强度数据的威布尔统计[Fine ceramics (ad-vanced ceramics，advanced technical ceramics) - Weibull statistics for strength data]
注:GB/T 40005 2021精细陶瓷强度数据的威布尔统计分析方法(ISO 20501,2019,MOD)
3术语和定义
下列术语和定义适用于本文件。
4原理
试样为矩形,其长度方向为CFRP层合板厚度方向。将试样放置在两个支座之间,在试样中间位置以恒定的速率施加载荷,直至试样外表面出现破坏。通过试样在弯曲试验中产生的拉伸应力和应变来测定厚度方向性能。由于强度依赖于尺寸效应,应通过拉伸强度和有效体积对尺寸效应进行定量估计。
5状态调节
5.1试样状态调节
如在材料规范中有明确规定,按规定对试样进行状态调节;如没有规定,选择ISO 291中最适合的条件对试样进行状态调节,除非相关方另有规定(例如:在高温或低温下进行试验)。优先选择ISO 291中标准环境(23 ℃,相对湿度为50%)条件对试样进行状态调节,当材料的弯曲性能对湿度不敏感时,不必控制湿度。
5.2试验的温度和湿度
应按5.1规定的条件进行试验。
6仪器设备
6.1试验机
试验机应符合ISO 5893和6.1及6.2的规定。试强湿率应能保持恒定,符合ISO 5893的规定。
6.2载荷和挠度指示装置
应有载荷指示装置﹐载荷的示值误差应小于0.1 N。
6.3试验夹具
6.3试验夹具
两个支座及中心加载压头的位置如图1所示。支座及加载压头的圆角半径分别为2 mm±0.2 mm和5 mm±o.2 mm(见 ISO 14125)。
6.4挠度测量系统
位移传感器应在挠度的整个测量范围内有效。使原位移传感器应在相关方之间达成一致。位移传感器运行所需的力不应超过试样破坏载荷的1%，
6.5数据采集系统
应能记录弯曲载荷与挠度数据。
6.6尺寸测量仪器
精度至少为0.005 mm的千分尺或类似精度尺寸测量仪器,用于测量试样的宽度(b)和厚度(t)。
7试样
7.1形状和尺寸
试样的形状和尺寸应符合表1的规定。
7.2试样制备
7.2.1通则
试验板的制备应按ISO1268-1和ISO 1268-4或其他规范/协议的规定。试样由试验板经机械加工制备﹐机械加工按ISO 2818的规定﹐应正确加工防止试样产生损伤。
7.2.2试验板
UD-CFRP试验板如图所示。面内纤维方向,垂直面内纤维方向和厚度方向分别定义为1方向、2方向和3方向。
7.3试样检查
试样应无扭曲,相邻的平面间应相互垂直,表面和边缘应无凹坑,划痕、麻点和毛刺。检查试样时，应将试样紧贴在直尺、直角尺或平板上,目视观测或用千分尺对试样进行测量检查。试样不符合要求时,应舍弃。
7.4试样数量
若不需要估算有效体积和威布尔模数﹐应至少测试5个试样。若需要估算有效体积和威布尔模数，应至少测试30个试样。
8试验步骤
8.1测量试样的宽度(b)和厚度(t ,精确至0.005 mm。
8.2放置试验夹具并调整跨距。跨距应大于试样厚度的25倍。
8.3试验速率按公式(1计算:
8.4试样居中放置在支座上。
8.5―在整个试验过程中,连续记录载荷和位移。
8.6如需要﹐用尺子或卡尺测量破坏位置。出现在加载压头区域附近的破坏模式为可接受的﹐见图3。
9计算
9.1厚度方向拉伸应力
9.2厚度方向拉伸强度
厚度方向拉伸强度按公式(3)计算:
9.3弯曲试验威布尔模数
通过弯曲试验按ISO 20501规定的程序估算威布尔模数。9.4弯曲试样有效体积
弯曲试样有效体积按公式(4)计算:
9.5厚度方向拉伸应变
厚度方向拉伸应变按公式(5)计算:
10精密度
为验证本试验方法而进行实验室间试验的细节以及从试验中获得的精密度数据见附录A。
11试验报告
试验报告应包含以下内容:
a）本文件名称和编号﹔
b)加载方法(弯曲方法);
c)被测材料的完整标识,包括类型、材料组成、来源和制造商信息等;
d试样的制备方法及其任何细节﹔
e)机械加工方法﹔
f试样数量﹔
g)试样尺寸﹔
h)试样状态调节的温度,湿度和持续时间;
i试验的温度和湿度﹔
j试验机和位移传感器的详细说明﹔
k)跨距;
l)弯曲试验的跨厚比(L/t) ;
m)试验速率﹔
n)厚度方向拉伸强度的平均值,如需要,给出标准差和平均值的95%置信区间;
o)厚度方向拉伸模量的平均值,如需要,给出标准差和平均值的95%置信区间;
p)厚度方向拉伸破坏应变的平均值,如需要﹐给出标准差和平均值的95%置信区间;
q)载荷位移曲线和应力应变曲线﹔
r)如需要,给出破坏位置﹔
s)如需要,给出威布尔模数﹔t如需要,给出有效体积;u)试验日期﹔
v)任何未按本文件规定的操作以及可能影响试验结果的任何事件。
附录A(资料性)实验室间试验获得的精密度数据
参考文献
