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范圍
本文件描述了測定碳纖維增強(qiáng)塑料復(fù)合材料(CFRP)層合板的厚度方向(面外)拉伸強(qiáng)度、拉伸破壞應(yīng)變和拉伸模量的彎曲試驗(yàn)方法。
本文件適用于碳纖維增強(qiáng)塑料復(fù)合材料單向(UD-CFRP)層合板。此外,由于厚度方向拉伸強(qiáng)度存在尺寸效應(yīng),還描述了有效體積的計(jì)算。
2規(guī)范性引用文件
下列文件中的內(nèi)容通過文中的規(guī)范性引用而構(gòu)成本文作必不可少的條款。其中,注日期的引用文件,僅該日期對(duì)應(yīng)的版本適用于本文件;不注日期的引用文件,其最新版本(包括所有的修改單)適用于本文件。
ISO 291塑料試樣狀態(tài)調(diào)節(jié)和試驗(yàn)的標(biāo)準(zhǔn)環(huán)境(Plastics - Standard atmospheres for conditioning and testing)
注:GB/T 2918-2018塑料試樣狀態(tài)得書和試驗(yàn)的標(biāo)準(zhǔn)環(huán)境(ISO 291:2008,MOD)
ISO 1268-1纖維增強(qiáng)塑料試驗(yàn)板制備方法第1部分:通則(Fibre-reinforced plastics - Methods of producing test plates - Part 1:General conditions)
注:GB/T 27797.1-2011纖維增強(qiáng)塑料﹑試驗(yàn)板制備方法第1部分:通則(ISO 1268-1:2001,IDT)
ISO 1268-4纖維增強(qiáng)塑料試驗(yàn)板制備方法第4部分:預(yù)浸料模塑(Fibre-reinforcedplastics - Methods of producing test plates - Part 4:Moulding of prepregs)
注:GB/T 27797.4-2013 纖維增強(qiáng)塑料試驗(yàn)板制備方法第4部分:預(yù)浸料模塑(ISO 1268-4:2005,IDT)
ISO 2818塑料機(jī)械加工制備試樣(Plastics - Preparation of test specimens by machining)
ISO 5893橡膠和塑料試驗(yàn)設(shè)備拉伸彎曲和壓縮型(恒速驅(qū)動(dòng)）規(guī)范[Rubber and plasticstest equipment - Tensile，flexural and compression types(constant rate of traverse) - Specification]
注:GB/T 17200-2008 橡膠塑料拉力壓力和彎曲試驗(yàn)機(jī)(恒速驅(qū)動(dòng)）技術(shù)規(guī)范(ISO 5893:2002,IDT)
ISO 20501精細(xì)陶瓷(先進(jìn)陶瓷先進(jìn)技術(shù)陶瓷)強(qiáng)度數(shù)據(jù)的威布爾統(tǒng)計(jì)[Fine ceramics (ad-vanced ceramics，advanced technical ceramics) - Weibull statistics for strength data]
注:GB/T 40005 2021精細(xì)陶瓷強(qiáng)度數(shù)據(jù)的威布爾統(tǒng)計(jì)分析方法(ISO 20501,2019,MOD)
3術(shù)語和定義
下列術(shù)語和定義適用于本文件。
4原理
試樣為矩形,其長度方向?yàn)镃FRP層合板厚度方向。將試樣放置在兩個(gè)支座之間,在試樣中間位置以恒定的速率施加載荷,直至試樣外表面出現(xiàn)破壞。通過試樣在彎曲試驗(yàn)中產(chǎn)生的拉伸應(yīng)力和應(yīng)變來測定厚度方向性能。由于強(qiáng)度依賴于尺寸效應(yīng),應(yīng)通過拉伸強(qiáng)度和有效體積對(duì)尺寸效應(yīng)進(jìn)行定量估計(jì)。
5狀態(tài)調(diào)節(jié)
5.1試樣狀態(tài)調(diào)節(jié)
如在材料規(guī)范中有明確規(guī)定,按規(guī)定對(duì)試樣進(jìn)行狀態(tài)調(diào)節(jié);如沒有規(guī)定,選擇ISO 291中最適合的條件對(duì)試樣進(jìn)行狀態(tài)調(diào)節(jié),除非相關(guān)方另有規(guī)定(例如:在高溫或低溫下進(jìn)行試驗(yàn))。優(yōu)先選擇ISO 291中標(biāo)準(zhǔn)環(huán)境(23 ℃,相對(duì)濕度為50%)條件對(duì)試樣進(jìn)行狀態(tài)調(diào)節(jié),當(dāng)材料的彎曲性能對(duì)濕度不敏感時(shí),不必控制濕度。
5.2試驗(yàn)的溫度和濕度
應(yīng)按5.1規(guī)定的條件進(jìn)行試驗(yàn)。
6儀器設(shè)備
6.1試驗(yàn)機(jī)
試驗(yàn)機(jī)應(yīng)符合ISO 5893和6.1及6.2的規(guī)定。試強(qiáng)濕率應(yīng)能保持恒定,符合ISO 5893的規(guī)定。
6.2載荷和撓度指示裝置
應(yīng)有載荷指示裝置﹐載荷的示值誤差應(yīng)小于0.1 N。
6.3試驗(yàn)夾具
6.3試驗(yàn)夾具
兩個(gè)支座及中心加載壓頭的位置如圖1所示。支座及加載壓頭的圓角半徑分別為2 mm±0.2 mm和5 mm±o.2 mm(見 ISO 14125)。
6.4撓度測量系統(tǒng)
位移傳感器應(yīng)在撓度的整個(gè)測量范圍內(nèi)有效。使原位移傳感器應(yīng)在相關(guān)方之間達(dá)成一致。位移傳感器運(yùn)行所需的力不應(yīng)超過試樣破壞載荷的1%，
6.5數(shù)據(jù)采集系統(tǒng)
應(yīng)能記錄彎曲載荷與撓度數(shù)據(jù)。
6.6尺寸測量儀器
精度至少為0.005 mm的千分尺或類似精度尺寸測量儀器,用于測量試樣的寬度(b)和厚度(t)。
7試樣
7.1形狀和尺寸
試樣的形狀和尺寸應(yīng)符合表1的規(guī)定。
7.2試樣制備
7.2.1通則
試驗(yàn)板的制備應(yīng)按ISO1268-1和ISO 1268-4或其他規(guī)范/協(xié)議的規(guī)定。試樣由試驗(yàn)板經(jīng)機(jī)械加工制備﹐機(jī)械加工按ISO 2818的規(guī)定﹐應(yīng)正確加工防止試樣產(chǎn)生損傷。
7.2.2試驗(yàn)板
UD-CFRP試驗(yàn)板如圖所示。面內(nèi)纖維方向,垂直面內(nèi)纖維方向和厚度方向分別定義為1方向、2方向和3方向。
7.3試樣檢查
試樣應(yīng)無扭曲,相鄰的平面間應(yīng)相互垂直,表面和邊緣應(yīng)無凹坑,劃痕、麻點(diǎn)和毛刺。檢查試樣時(shí)，應(yīng)將試樣緊貼在直尺、直角尺或平板上,目視觀測或用千分尺對(duì)試樣進(jìn)行測量檢查。試樣不符合要求時(shí),應(yīng)舍棄。
7.4試樣數(shù)量
若不需要估算有效體積和威布爾模數(shù)﹐應(yīng)至少測試5個(gè)試樣。若需要估算有效體積和威布爾模數(shù)，應(yīng)至少測試30個(gè)試樣。
8試驗(yàn)步驟
8.1測量試樣的寬度(b)和厚度(t ,精確至0.005 mm。
8.2放置試驗(yàn)夾具并調(diào)整跨距。跨距應(yīng)大于試樣厚度的25倍。
8.3試驗(yàn)速率按公式(1計(jì)算:
8.4試樣居中放置在支座上。
8.5―在整個(gè)試驗(yàn)過程中,連續(xù)記錄載荷和位移。
8.6如需要﹐用尺子或卡尺測量破壞位置。出現(xiàn)在加載壓頭區(qū)域附近的破壞模式為可接受的﹐見圖3。
9計(jì)算
9.1厚度方向拉伸應(yīng)力
9.2厚度方向拉伸強(qiáng)度
厚度方向拉伸強(qiáng)度按公式(3)計(jì)算:
9.3彎曲試驗(yàn)威布爾模數(shù)
通過彎曲試驗(yàn)按ISO 20501規(guī)定的程序估算威布爾模數(shù)。9.4彎曲試樣有效體積
彎曲試樣有效體積按公式(4)計(jì)算:
9.5厚度方向拉伸應(yīng)變
厚度方向拉伸應(yīng)變按公式(5)計(jì)算:
10精密度
為驗(yàn)證本試驗(yàn)方法而進(jìn)行實(shí)驗(yàn)室間試驗(yàn)的細(xì)節(jié)以及從試驗(yàn)中獲得的精密度數(shù)據(jù)見附錄A。
11試驗(yàn)報(bào)告
試驗(yàn)報(bào)告應(yīng)包含以下內(nèi)容:
a）本文件名稱和編號(hào)﹔
b)加載方法(彎曲方法);
c)被測材料的完整標(biāo)識(shí),包括類型、材料組成、來源和制造商信息等;
d試樣的制備方法及其任何細(xì)節(jié)﹔
e)機(jī)械加工方法﹔
f試樣數(shù)量﹔
g)試樣尺寸﹔
h)試樣狀態(tài)調(diào)節(jié)的溫度,濕度和持續(xù)時(shí)間;
i試驗(yàn)的溫度和濕度﹔
j試驗(yàn)機(jī)和位移傳感器的詳細(xì)說明﹔
k)跨距;
l)彎曲試驗(yàn)的跨厚比(L/t) ;
m)試驗(yàn)速率﹔
n)厚度方向拉伸強(qiáng)度的平均值,如需要,給出標(biāo)準(zhǔn)差和平均值的95%置信區(qū)間;
o)厚度方向拉伸模量的平均值,如需要,給出標(biāo)準(zhǔn)差和平均值的95%置信區(qū)間;
p)厚度方向拉伸破壞應(yīng)變的平均值,如需要﹐給出標(biāo)準(zhǔn)差和平均值的95%置信區(qū)間;
q)載荷位移曲線和應(yīng)力應(yīng)變曲線﹔
r)如需要,給出破壞位置﹔
s)如需要,給出威布爾模數(shù)﹔t如需要,給出有效體積;u)試驗(yàn)日期﹔
v)任何未按本文件規(guī)定的操作以及可能影響試驗(yàn)結(jié)果的任何事件。
附錄A(資料性)實(shí)驗(yàn)室間試驗(yàn)獲得的精密度數(shù)據(jù)
參考文獻(xiàn)
