GB/T 410492021 PDF in English
GB/T 410492021 (GB/T410492021, GBT 410492021, GBT410492021)
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Test method for flexural properties of fibre metal laminates
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Standards related to (historical): GB/T 410492021
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GB/T 410492021: PDF in English (GBT 410492021) GB/T 410492021
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.150.10
CCS Y 80
Test method for flexural properties of fibre metal laminates
ISSUED ON: DECEMBER 31, 2021
IMPLEMENTED ON: JULY 1, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 4
4 Test principle ... 5
5 Test equipment ... 6
6 Samples ... 7
7 State regulation ... 8
8 Test procedures ... 8
9 Calculation and result presentation ... 10
10 Test report... 13
Test method for flexural properties of fibre metal laminates
1 Scope
This document specifies the test principle, test equipment, sample, state regulation, test
procedure, calculation and result presentation, and test report of the test method for
flexural properties of fibre metal laminates.
This document applies to the determination of threepoint flexural strength, flexural
modulus, flexural stress, and loaddeflection curves of fibre metal laminates undergoing
bending failure.
2 Normative references
The following documents contain the provisions which, through normative reference in
this document, constitute the essential provisions of this document. For the dated
referenced documents, only the versions with the indicated dates are applicable to this
document; for the undated referenced documents, only the latest version (including all
the amendments) is applicable to this document.
GB/T 14462005 Fiberreinforced plastics composites  The generals for
determination of properties
GB/T 2918 Plastics  Standard atmospheres for conditioning and testing
GB/T 8170 Rules of rounding off for numerical values & expression and judgment
of limiting values
JJG 139 Verification regulation of Tension, Compression and Universal Testing
Machines
3 Terms and definitions
The following terms and definitions apply to this document.
3.1 fibre metal laminates; FMLs
It is an interlayer hybrid composite material formed by alternately laying metal sheets
(aluminum alloy, titanium alloy, etc.) and fibre (glass fibre, carbon fibre, aramid fibre,
etc.) composite materials under a certain temperature and pressure.
3.2 flexural stress
Bending moment regularization.
Note 1: The stress of the outer surface layer of the sample when it is assumed that the stress caused by
bending deformation is linearly distributed.
Note 2: The unit is megapascal (MPa).
3.3 flexural strength
Under bending failure, the flexural stress of the specimen when the damage load or the
maximum load is reached.
Note: The unit is megapascal (MPa).
3.4 span
The distance between the central axes of the two supports on the testing machine.
Note: The unit is millimeter (mm).
3.5 deflection
The maximum height difference between the normal line of the deformation position
of the sample surface during bending and the initial position.
Note: The unit is millimeter (mm).
3.6 flexural strain
The rate of change in length of the outer surface layer of the sample at the midpoint of
the span, expressed as a percentage.
3.7 flexural modulus
The value derived from the slope of the initial section on a bending stressbending strain
curve or bending loaddeflection curve.
Note: The unit is megapascal (MPa).
4 Test principle
With unconstrained support, the sample is destroyed at a constant loading rate by three
point bending. Throughout the process, measure the load applied to the sample and the
deflection or bending strain of the sample to determine the flexural strength, flexural
modulus, and the relationship between flexural stress and flexural strain.
Note 3: The data obtained from tests under different spantothickness ratios cannot be compared.
8.4 Sample installation
Mark the tension surface of the sample, and place the sample symmetrically on the two
supports. If necessary, place a thin sheet or a thin spacer between the upper surface of
the sample and the loading indenter to prevent the sample from failing under pressure.
When using strain gauges, stick the strain gauges at the center of the span below the
sample along the parallel length direction; when using a deflectometer, place the
deflectometer at the center of the span and perpendicular to the plane of the sample.
8.5 Test speed
The loading rate shall be between 1 mm/min~2 mm/min and kept constant.
8.6 Test
Apply the load uniformly across the width of the sample by a loading indenter located
at the midpoint of the span until the sample is destroyed or the load drops by 30%.
Record the failure load to determine the flexural strength, and record the loaddeflection
curve or the loadflexural strain curve to determine the flexural modulus.
8.7 Data collection
Record the load value of the whole test process, and take the happening of the effective
bending damage such as fibre damage or outer metal damage as the principle of data
collection. The samples that show interlaminar shear failure, obvious internal defects,
or damage beyond the middle onethird of the span shall be discarded. When the number
of valid test results in the same batch is less than 5, the number of tested samples shall
be increased to ensure the number of valid results reaches 5.
8.8 Failure modes
The fibre metal laminate will have the following failure modes under the test of this
method.
a) Acceptable flexural failure modes:
1) Fibre failure, see Figure 4 a);
2) The outer metal is damaged, see Figure 4 b).
b) Unacceptable failure modes:
1) Interlaminar shear failure, see Figure 4 c);
Where:
——  The arithmetic mean of the flexural strength or flexural modulus of the sample,
in megapascals (MPa);
Xi  The flexural strength or flexural modulus of the sample, in megapascals (MPa);
n  Number of samples;
s  Standard deviation, in megapascals (MPa).
9.5 Numerical rounding
The numerical rounding shall be carried out in accordance with GB/T 8170, the flexural
strength is rounded to four significant digits, the standard deviation is rounded to three
significant digits, and the flexural modulus is rounded to three significant digits.
10 Test report
Unless otherwise agreed by the parties, the test report shall include at least the following
information:
a) Information on the material category of the sample, including the orientation and
specific structure of the sample fibre layup;
b) Information on test conditions;
c) The number of the document used;
d) The model and serial number of the instrument used;
e) Fillet radius of the loading indenter and supports;
f) Sample source information;
g) The unique identification of the sample;
h) All information on sample preparation;
i) Span;
...... Source: Above contents are excerpted from the PDF  translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
