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GB/T 8813-2020 (GB/T8813-2020)

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GB/T 8813-2020: PDF in English (GBT 8813-2020)
GB/T 8813-2020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.100
G 31
GB/T 8813-2020 / ISO 844:2014
Replacing GB/T 8813-2008
Rigid cellular plastics - Determination of compression
properties
(ISO 844:2014, IDT)
ISSUED ON: JULY 21, 2020
IMPLEMENTED ON: FEBRUARY 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 5 
2 Normative references ... 5 
3 Terms and definitions ... 5 
4 Symbols ... 6 
5 Principle ... 7 
6 Equipment ... 7 
7 Sample ... 8 
8 Test procedure ... 9 
9 Result expression ... 10 
10 Precision ... 13 
11 Test report ... 13 
References ... 15 
Foreword
This Standard was drafted in accordance with the rules given in GB/T 1.1-2009.
This Standard replaces GB/T 8813-2008, “Rigid cellular plastics -
Determination of compression properties”. Compared with GB/T 8813-2008,
the major changes of this Standard are as follows:
-- Modify the scope (see Chapter 1, Chapter 1 of version 2008);
-- Modify symbols and abbreviations (see Chapter 4; Chapter 4 of version
2008);
-- Modify the displacement measurement (see 6.2.1; 6.2.1 of version 2008);
-- Modify the state adjustment (see 7.4; 7.4 of version 2008);
-- Modify the test procedures (see Chapter 8; Chapter 8 of version 2008);
-- Modify the overview (see 9.1; 9.1 of version 2008);
-- Modify the units of compressive strength and compressive stress at 10%
relative deformation (see 9.2.1, 9.3; 9.2.1, 9.3 of version 2008);
-- Modify the compressive modulus of elasticity (see 9.4; 9.4 of version 2008);
-- Modify the test report (see Chapter 11, Chapter 11 of version 2008);
This Standard uses the translation method that is equivalent to ISO 844:2014,
“Rigid cellular plastics - Determination of compression properties”.
The documents of our country that have a consistent correspondence with the
international documents that are referenced in this Standard are as follows:
-- GB/T 6342-1996, Cellular plastics and rubbers - Determination of linear
dimensions (ISO 1923:1981, IDT).
This Standard was proposed by China National Light Industry Council.
This Standard shall be under the jurisdiction of National Technical Committee
48 on Plastic Products of Standardization Administration of China (SAC/TC 48).
The drafting organizations of this Standard: Light Industry Plastics Processing
Application Research Institute, Hebei Wuzhou Kaiyuan Environmental
Protection New Material Co., Ltd., Wuhan Industrial Control Inspection and
Testing Co., Ltd., Shanghai Pugong Testing Technology Co., Ltd., China
National Centre for Quality Supervision & Test of Plastic Products (Beijing).
Rigid cellular plastics - Determination of compression
properties
1 Scope
This Standard specifies methods for determining the following parameters:
a) Compressive strength and relative deformation; or
b) Compressive stress at 10% relative deformation; and
c) Compression modulus of rigid cellular plastics, if needed.
There are two methods:
-- Method A uses beam displacement to determine compression properties.
When it is necessary to determine the compressive stress at 10% relative
deformation, use Method A.
-- Method B uses a strain measurement device (contact extensometer) or a
similar device that is fixed on the sample to directly measure the
deformation of the sample. When it is necessary to determine the
compression modulus, use Method B.
Note: Both method A and method B can determine the compressive strength
(at maximum load).
2 Normative references
The following documents are indispensable for the application of this document.
For dated references, only the dated version applies to this document. For
undated references, the latest edition (including all amendments) applies to this
document.
ISO 1923, Cellular plastics and rubbers - Determination of linear dimensions
3 Terms and definitions
The following terms and definitions are applicable to this document.
3.1 Relative deformation
σm: compressive strength, MPa.
σ10: compressive stress at 10% relative deformation, MPa.
xe: displacement corresponding to the compressive force Fe within the
proportional limit, mm.
xm: displacement corresponding to the maximum compressive force Fm when
the relative deformation ε<10%, mm.
x10: displacement when the relative deformation is 10%, mm.
5 Principle
Apply a vertical compressive force to the surface of the sample, so as to
calculate the maximum stress that the sample bears. If the relative deformation
corresponding to the maximum stress is less than 10%, call it “compressive
strength”. If the relative deformation corresponding to the maximum stress
reaches or exceeds 10%, take the compressive stress at 10% relative
deformation as the test result, which is called “compressive stress at 10%
relative deformation”.
6 Equipment
6.1 Compression testing machine
The range of force and displacement of the used compression testing machine
shall meet the requirements of this Standard. Two square or round parallel
plates with polished surface and no deformation are required. The side length
(or diameter) of the plate is at least 100 mm and larger than the pressure
surface of the sample; one of them is fixed and the other can be moved at a
constant rate according to the conditions that are specified in Chapter 8. The
two plates shall always be kept level.
6.2 Displacement and force measurement device
6.2.1 Measurement of displacement
Method A -- The compression testing machine shall be equipped with a device
that can continuously measure the displacement x of the moving plate; the
accuracy is ±5% or ±0.1 mm; if the latter is more accurate, select the latter (see
the second paragraph of 6.2.2).
It is not allowed to stack several samples for testing.
The results that are measured on samples of different geometries and
thicknesses are not comparable.
7.2 Preparation
When preparing the sample, its pressure surface shall be perpendicular to the
direction in which the product is stressed. To understand the complete
characteristics of anisotropic materials, or to know the main direction of
anisotropic materials, prepare multiple sets of samples.
In general, the characteristics of anisotropic body are represented by a plane
and its orthogonal plane; so, two sets of samples are considered.
The preparation of sample shall not change the structure of the foam material.
If the product does not retain the molded skin during use, the skin shall be
removed.
7.3 Quantity
When taking samples from block materials or thick plates of rigid cellular plastic
products, refer to the provisions in the relevant foam plastic product standards
for the sampling method and quantity. In the absence of relevant regulations,
take at least 5 samples.
7.4 State adjustment
According to one of the following conditions, adjust for at least 6 h:
a) Temperature of (23±2) °C, relative humidity of (50±10) %;
b) Temperature of (23±5) °C, relative humidity of 50+20 -10 %;
c) Temperature of (27±5) °C, relative humidity of 65+20 -10 %.
8 Test procedure
The test condition shall be the same as the condition of the sample state
adjustment.
According to the provisions of ISO 1923, measure the three-dimensional size
of each sample. Place the sample in the center between the two parallel plates
of the compression testing machine; compress the sample at a rate of 10% of
the initial thickness of the sample per minute as much as possible, until the
compressive strength σm and/or the compressive stress at 10% relative
deformation σ10 are measured.
......
 
(Above excerpt was released on 2020-11-28, modified on 2021-06-07, translated/reviewed by: Wayne Zheng et al.)
Source: https://www.chinesestandard.net/PDF.aspx/GBT8813-2020