Tensile tests on specimens are used to characterize material behavior during processing.
Material characteristic values determined under standardized processing conditions using standard specimens may differ significantly in some respects from the properties actually existing in a pipe. This is because of the processing state, which is completely different in an extruded pipe as compared to an injection-molded specimen.
To characterize this property, specimens are removed from the pipe wall along the length of the pipe. The methodology of specimen removal and testing is described for example in Parts 1 to 3 of ISO 6259 . Depending on the pipe material and the wall thickness of the pipe, various specimen shapes are used, each of which is intended for a different type of specimen holder.
Specimen strain is determined directly on the specimen using a mechanical or optical long-travel extensometer.
Testing welded and joint seams
A special form of tensile test is used for welded and joint seams. For this the specimen is removed from the pipe in such a way that the weld or joint seam is located in the free gauge-length area of the specimen. Inhomogeneous strain distribution can be anticipated, making direct extension measurement on the specimen unnecessary in this case. The result obtained is the tensile strength of the joint and, where applicable, a comparison with the tensile strength of the raw material.
Standards for tensile tests on plastic pipes
ISO 6259-1 Thermoplastics pipes - determination of tensile properties - Part 1: general test method
ISO 6259-2 Thermoplastics pipes - determination of tensile properties - Part 2: pipes made of PVC-U
ISO 6259-3 Thermoplastics pipes - determination of tensile properties - Part 3: polyolefin pipes
ISO 8521 Plastics piping systems -- Glass-reinforced thermosetting plastics (GRP) pipes -- Test methods for the determination of the apparent initial circumferential tensile strength
ISO 8513 Plastics piping systems -- Glass-reinforced thermosetting plastics (GRP) pipes -- Determination of longitudinal tensile properties
ASTM D2105 Tensile Properties of “Fiberglass” (Glass-Fiber-Reinforced Thermosetting-Resin) Pipe and Tube
ASTM D2290 Apparent Hoop Tensile Strength of Plastic or Reinforced Plastic Pipe
EN 1393 Plastics piping systems - glass-reinforced thermosetting plastics (GRP) pipes; determination of initial longitudinal tensile properties
EN 1394 Plastics piping systems - glass-reinforced thermosetting plastics (GRP) pipes - determination of the apparent initial circumferential tensile strength