By far the most common tests performed
on plastics are tensile strength, tensile modulus, flexural
strength and flexural modulus. ASTM D638 and ISO 527 are tensile
tests and flexural testing (ASTM D790, ASTM D6272 and ISO 178)
are performed by placing a test specimen on two supports on
the baseplate of the machine. The crosshead pushes on the unsupported
center of the specimen until it bends or breaks. Compression
tests include testing rigid plastic foams per ASTM D1621 and
ISO 844, and bottle crush tests. Shear tests and shear strength
is obtained by placing a specimen in a punch-type shear fixture.
The punch is pushed down at a slow rate and results calculated
as the force by area sheared.