GB/T 8813-1988 Compression test method for rigid cellular plastics

GB/T 8813-1988 Compression test method for rigid foam plastics GB/T8813-1988 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Test method for compression
of rigid cellular plastics
UDC678.5/7.074
：620.173
GB 8813—88
ISO 844---1978
This standard is equivalent to the international standard ISO844—1978 "Compression test of rigid cellular plastics". 1 Scope of application
This standard is applicable to the determination of the compressive strength and relative deformation of rigid cellular plastics, or the compressive stress when the relative deformation is 10%. 2 Reference standards
GB2918 Standard environment for conditioning and testing of plastic specimens GB6342 Determination of linear dimensions of foam plastics and rubber 3 Terminology
3.1 Relative deformation (e)
The quotient obtained by dividing the change in thickness of the specimen after compression by the initial thickness of the specimen, expressed as a percentage. 3.2 Compression strength (αm)
The quotient obtained by dividing the maximum compression force F. obtained when the relative deformation ε is less than 10% by the initial area of ​​the specimen cross section. The relative deformation corresponding to αm is recorded as Em.
3.3 Compression stress when the relative deformation is 10% (α10) The quotient obtained by dividing the compression force F1 when the relative deformation is 10% (e1o) by the initial area of ​​the cross section. 4 Equipment
4.1 Compression testing machine
The force and displacement range of the compression testing machine used should meet the requirements of this standard. Two square or circular parallel plates with polished and non-deformable surfaces shall be available, with a side length or diameter of at least 10 cm, one of which is fixed and the other can be moved at a constant rate according to the conditions specified in Chapter 5.
4.2 Device for measuring force and displacement.
4.2.1 Device for measuring force
A force sensor is installed on one of the plates of the compression tester. The sensor should be able to continuously measure the reaction force F of the specimen on the plate during the test (the deformation of the specimen itself during the test can be ignored) with an accuracy of ±1%. 4.2.2 Device for measuring displacement
The compression tester should be equipped with a device that can continuously measure the displacement of the movable plate with an accuracy of ±5%. 4.2.3 Calibration
Pre-calibrate the readings of the compression tester's measuring device. All standard mass blocks should be consistent with the sensitivity of the applied force, and the accuracy should be higher than that specified in 4.2.1. The accuracy of the standard sheet should also be higher than that specified in 4.2.1. Approved by the Ministry of Light Industry of the People's Republic of China on February 13, 1988 418
Implementation on July 1, 1988
5 Samples
5.1 Sample size
GB 8813-88
For products that do not retain the molded skin during use, the skin should be removed and the sample thickness should be 50±1mm. For products that need to have a molded skin during use, the sample should be the original thickness of the entire product, but at least 10mm, and the maximum thickness should not exceed the width or diameter of the sample. The base surface of the sample is square or circular, with an area between 25.0 and 230.0cm2. The parallelism tolerance of the two parallel surfaces of the sample should not exceed 1%. It is recommended to use a regular quadrangular prism sample with a base side length of 100.0±1.0mm.
The results of samples of different thicknesses are incomparable. 5.2 Preparation of samples
The sample should not change the original structure of the foam material. The specimen should be prepared so that its reference surface is perpendicular to the direction in which the product will be subjected to pressure when in use. If it is necessary to understand the complete characteristics of anisotropic materials, or if the main aspects of inhomogeneous materials are unknown, two sets of specimens should be prepared. The characteristics of anisotropic bodies are represented by a plane and its orthogonal planes.
The specimen is not allowed to be stacked by several thin sheets.
5.3 Number of specimens
The specimens should be prepared from the block material or thick plate of rigid foam plastic products. The sampling method and quantity can refer to the provisions in the relevant foam plastic product standards, but at least 5 specimens should be taken. 5.4 The state adjustment of the specimen and the standard environment of the test are carried out in accordance with the temperature of 23±2℃ and relative humidity of 45%~55% specified in GB2918. 6 Test steps
Measure the size of the specimen according to the method specified in GB6342, and then place the specimen in the center of the two flat plates of the compression tester. The movable plate compresses the specimen at a constant rate. wwW.bzxz.Net
The relative deformation must be at least 10%.
7 Expression of results
7.1 Compression strength and relative deformation
7.1.1 Compression strength
Calculate the compression strength αm (kPa) according to formula (1): am=
Where: am
Compression strength, kPa;
Fm——maximum compression force, N;
S. Initial cross-sectional area of ​​the specimen, mm2. 7.1.2 Relative deformation
....( 1)
Use a ruler to extend the straight line with the largest slope on the force-deformation curve to the force zero line. The intersection point is the "deformation zero point". Measure the entire displacement (X) from the "deformation zero point" to the maximum pressure on the specimen. The following figures are two examples. Calculate the relative deformation em according to formula (2):
Em(%) =
Where: Em - relative deformation of the specimen when subjected to maximum compression force, %, Xm displacement when the maximum compression force is reached, mm, Xm
- initial thickness of the specimen, mm.
GB8813-88
If there is no obvious straight line portion on the force-deformation curve, or the "zero deformation point" obtained by this method is a negative value, then the "zero deformation point" should be the deformation corresponding to the compressive stress of 100±10 kPa. 7.2 Compressive stress when the relative deformation is 10% Calculate the compressive stress when the relative deformation is 10% according to formula (3): Gro
Where: α1o-
Fio -m
- compressive stress when the relative deformation is 10%, kPa; - force to produce 10% relative deformation of the specimen, N; initial cross-sectional area of ​​the specimen, mm2.
Displacement zero point
Fm—-maximum compression force: F10-compression force when relative deformation is 10%; Xm--displacement when maximum compression force, X10-displacement when relative deformation is 10%
8Test report
The test report should include the following contents:
Type and variety of foam plastic products;
If the specimen does not adopt the size recommended in 5.1, the specimen size should be indicated; b.
The relationship between the direction of applied pressure and the anisotropic body or product geometry; ·(3)
The average value of the test results, expressed as: compressive strength (α) and its relative deformation (ε), or compressive stress (a) when the relative deformation is 10%
If the deviation between the individual test values ​​is greater than 10%, give the individual test results and indicate the operating procedures that are different from this standard. f.
Additional Notes:
GB8813-88
This standard was proposed by the Ministry of Light Industry of the People's Republic of China. This standard is under the jurisdiction of the Plastic Processing and Applied Science Research Institute of the Ministry of Light Industry. This standard was drafted by the Shanghai Plastic Products Research Institute. The main drafter of this standard was Feng Wei.
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