ISO 844:2007 pdf free download.Rigid cellular plastics — Determination of compression properties.
ISO 844:2007 specifies a method of determining
a) the compressive strength and corresponding relative deformation
or
b) the compressive stress at 10 % relative deformation
and
c) when desired, the compressive modulus of rigid cellular plastics.
2 Normative references
ISO 1923, Cellular plastics and rubbers-Determination of linear dimensions;
5 Principle
A compressive force is applied in an axial direction to the faces of a rectangular parallelepiped test specimen The maximum stress supported by the test specimen is calculated.
If the value of the maximum stress corresponds to a relative deformation of less than 10 %， it is noted as the “compressive stren Othewise the compressive stress at 10 relatie deformation is calculated and its value noted as the”compressive stress at 10 relative deformation.
6 Apparatus
6.1 Compression-testing machine
Use a compression-testing machine suited to the range of force and displacement involved and having two square or circular plane, parallel plates which are polished and cannot be deformed and of which the length of one side(or the diameter)is at least 10 cm. One of the plates shall be fixed and the other movable; the latter shall be capable of moving at a constant rate of displacement in accordance with the conditions laid down in Clause 8. Neither plate shall be self-aligning.
6.2 Devices for measuring displacement and force
6.2.1 Measurement of displacement
The compression-testing machine shall be fitted with a system allowing continuous measurement of the displacement x of the movable plate with an accuracy of *5% or*0, 1 mm if this latter value is a more accurate measurement(see Note to 6.2.2).