Information on the most widely used ASTM standards within the materials testing industry
ASTM D695
ASTM D695 Compression Testing fixture Rigid Plastics is used to
determine the compressive strength of rigid unreinforced and reinforced
plastic, including high-modulus composites, through a process of
straining and loading the plastic at relatively low rates of strain. It
enables replication of application-specific conditions. The compressive
property information provides a standard and consistent means to compare
materials for research and development, quality control, acceptance or
rejection under specifications, and other material evaluation processes.
Critical
compressive properties include modulus of elasticity, yield stress,
deformation beyond yield point, and compressive strength (unless the
material merely flattens but does not fracture). According to ASTM D695,
the specimen is placed between compressive plates parallel to the
specimen surface, and compressed along its major axis at constant rate
of displacement until the specimen fractures or until the load or the
decrease in length reaches a predetermined value. An extensometer
attached to the fixture is used to determine the modulus of elasticity.
When performing compression testing, it has been found that specimen
alignment plays an important role in achieving even load distribution,
which contributes to the consistency of the results.
General introduction
The standard specimen for strength determination is a right cylinder or prism whose length is twice its principal width or diameter. If the specimen is too thin, an anti-buckling support jig should be used to prevent the specimen from buckling.
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Specification
Specimen size:
Specimens can either be blocks or
cylinders. For ASTM, the typical blocks are 12.7 x 12.7 x 25.4mm (½ by ½
by 1 in).
and the cylinders are 12.7mm (½ in) in diameter and 25.4mm (1 in) long.
For ISO, the preferred specimens are 50 x 10 x 4mm for modulus and 10 x 10 x 4mm for strength.
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