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塑料復合材料(CFRP)層合板的厚度方向(面外)拉伸強度、拉伸破壞應變和拉伸模量的彎曲試驗方法。
本文件適用于碳纖維增強塑料復合材料單向(UD-CFRP)層合板。此外,由于厚度方向拉伸強度存在尺寸效應,還描述了有效體積的計算。
2規范性引用文件
下列文件中的內容通過文中的規范性引用而構成本文作必不可少的條款。其中,注日期的引用文件,僅該日期對應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塑料試樣狀態調節和試驗的標準環境(Plastics - Standard atmospheres for conditioning and testing)
注:GB/T 2918-2018塑料試樣狀態得書和試驗的標準環境(ISO 291:2008,MOD)
ISO 1268-1纖維增強塑料試驗板制備方法第1部分:通則(Fibre-reinforced plastics - Methods of producing test plates - Part 1:General conditions)
注:GB/T 27797.1-2011纖維增強塑料﹑試驗板制備方法第1部分:通則(ISO 1268-1:2001,IDT)
ISO 1268-4纖維增強塑料試驗板制備方法第4部分:預浸料模塑(Fibre-reinforcedplastics - Methods of producing test plates - Part 4:Moulding of prepregs)
注:GB/T 27797.4-2013 纖維增強塑料試驗板制備方法第4部分:預浸料模塑(ISO 1268-4:2005,IDT)
ISO 2818塑料機械加工制備試樣(Plastics - Preparation of test specimens by machining)
ISO 5893橡膠和塑料試驗設備拉伸彎曲和壓縮型(恒速驅動）規范[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機(恒速驅動）技術規范(ISO 5893:2002,IDT)
ISO 20501精細陶瓷(先進陶瓷先進技術陶瓷)強度數據的威布爾統計[Fine ceramics (ad-vanced ceramics，advanced technical ceramics) - Weibull statistics for strength data]
注:GB/T 40005 2021精細陶瓷強度數據的威布爾統計分析方法(ISO 20501,2019,MOD)
3術語和定義
下列術語和定義適用于本文件。
4原理
試樣為矩形,其長度方向為CFRP層合板厚度方向。將試樣放置在兩個支座之間,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破壞。通過試樣在彎曲試驗中產生的拉伸應力和應變來測定厚度方向性能。由于強度依賴于尺寸效應,應通過拉伸強度和有效體積對尺寸效應進行定量估計。
5狀態調節
5.1試樣狀態調節
如在材料規范中有明確規定,按規定對試樣進行狀態調節;如沒有規定,選擇ISO 291中最適合的條件對試樣進行狀態調節,除非相關方另有規定(例如:在高溫或低溫下進行試驗)。優先選擇ISO 291中標準環境(23 ℃,相對濕度為50%)條件對試樣進行狀態調節,當材料的彎曲性能對濕度不敏感時,不必控制濕度。
5.2試驗的溫度和濕度
應按5.1規定的條件進行試驗。
6儀器設備
6.1試驗機
試驗機應符合ISO 5893和6.1及6.2的規定。試強濕率應能保持恒定,符合ISO 5893的規定。
6.2載荷和撓度指示裝置
應有載荷指示裝置﹐載荷的示值誤差應小于0.1 N。
6.3試驗夾具
6.3試驗夾具
兩個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
位移傳感器應在撓度的整個測量范圍內有效。使原位移傳感器應在相關方之間達成一致。位移傳感器運行所需的力不應超過試樣破壞載荷的1%，
6.5數據采集系統
應能記錄彎曲載荷與撓度數據。
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符合表1的規定。
7.2試樣制備
7.2.1通則
試驗板的制備應按ISO1268-1和ISO 1268-4或其他規范/協議的規定。試樣由試驗板經機械加工制備﹐機械加工按ISO 2818的規定﹐應正確加工防止試樣產生損傷。
7.2.2試驗板
UD-CFRP試驗板如圖所示。面內纖維方向,垂直面內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
試樣應無扭曲,相鄰的平面間應相互垂直,表面和邊緣應無凹坑,劃痕、麻點和毛刺。檢查試樣時，應將試樣緊貼在直尺、直角尺或平板上,目視觀測或用千分尺對試樣進行測量檢查。試樣不符合要求時,應舍棄。
7.4試樣數量
若不需要估算有效體積和威布爾模數﹐應至少測試5個試樣。若需要估算有效體積和威布爾模數，應至少測試30個試樣。
8試驗步驟
8.1測量試樣的寬度(b)和厚度(t ,精確至0.005 mm。
8.2放置試驗夾具并調整跨距。跨距應大于試樣厚度的25倍。
8.3試驗速率按公式(1計算:
8.4試樣居中放置在支座上。
8.5―在整個試驗過程中,連續記錄載荷和位移。
8.6如需要﹐用尺子或卡尺測量破壞位置。出現在加載壓頭區域附近的破壞模式為可接受的﹐見圖3。
9計算
9.1厚度方向拉伸應力
9.2厚度方向拉伸強度
厚度方向拉伸強度按公式(3)計算:
9.3彎曲試驗威布爾模數
通過彎曲試驗按ISO 20501規定的程序估算威布爾模數。9.4彎曲試樣有效體積
彎曲試樣有效體積按公式(4)計算:
9.5厚度方向拉伸應變
厚度方向拉伸應變按公式(5)計算:
10精密度
為驗證本試驗方法而進行實驗室間試驗的細節以及從試驗中獲得的精密度數據見附錄A。
11試驗報告
試驗報告應包含以下內容:
a）本文件名稱和編號﹔
b)加載方法(彎曲方法);
c)被測材料的完整標識,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節﹔
e)機械加工方法﹔
f試樣數量﹔
g)試樣尺寸﹔
h)試樣狀態調節的溫度,濕度和持續時間;
i試驗的溫度和濕度﹔
j試驗機和位移傳感器的詳細說明﹔
k)跨距;
l)彎曲試驗的跨厚比(L/t) ;
m)試驗速率﹔
n)厚度方向拉伸強度的平均值,如需要,給出標準差和平均值的95%置信區間;
o)厚度方向拉伸模量的平均值,如需要,給出標準差和平均值的95%置信區間;
p)厚度方向拉伸破壞應變的平均值,如需要﹐給出標準差和平均值的95%置信區間;
q)載荷位移曲線和應力應變曲線﹔
r)如需要,給出破壞位置﹔
s)如需要,給出威布爾模數﹔t如需要,給出有效體積;u)試驗日期﹔
v)任何未按本文件規定的操作以及可能影響試驗結果的任何事件。
附錄A(資料性)實驗室間試驗獲得的精密度數據
參考文獻
