BS EN ISO 844:2014 pdf free.Rigid cellular plastics – Determination of compression properties.
BS EN ISO 844 specifies a method of determining:
a) the compressive strength and corresponding relative deformation,
b) the compressive stress at 10 % relative deformation, and
c) when desired, the compressive modulus of rigid cellular plastics. There are two procedures:
— Procedure A employs crosshead motion for determination of compressive properties. Procedure A is intended to be used when compressive stress at 10 % relative deformation has to be determined.
— Procedure B employs strain measuring devices mounted on the specimen (contact extensometer) or similar device which measures directly sample deformation. Procedure B is intended to be used when compressive modulus has to be determined.
NOTE Compressive strength (at maximum load) can be determined either with Procedure A and B.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 1923, Cellular plastics and rubbers — Determination of linear dimensions
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 relative deformation ratio of the reduction (in relation to its initial value) in thickness of the test specimen (Procedure A) or of extensometer gauge length (Procedure B)
3.2 compressive strength Om maximum compressive force Fm divided by the initial cross-sectional area of the test specimen when the relative deformationεis< 10 %
5 Principle
A compressive force is applied in an axial direction to the faces of 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 strengthH. Otherwise, the compressive stress at 10 % relative deformation is calculated and its value noted as the “compressive stress at 10 % relative deformation”.BS EN ISO 844 pdf free download.