Significance and Use
Shear tests provide information about the shear properties of plastic lumber when employed under conditions approximating those under which the tests are made. For many materials, there may be a specification that requires the use of this test method, but with some procedural-modifications that take precedence when adhering to the specification. Therefore, it is advisable to refer to that material specification before using this test method. Table 1 in Classification D 4000 lists the ASTM materials standards that currently exist.
Shear properties are limited to shear strength only. In the case of a material that fails in shear by a fracture, the shear strength has a very definite value. In the case of a material that does not fail in shear by a fracture, the shear strength is based on the maximum load carried by the test specimen. Many plastic lumber materials may not fail in the classic shear mode; that is, separation of the test specimen into two pieces by failure along the critical shear surface.
Shear tests provide a standard method of obtaining data for research and development, design, quality control, acceptance, or rejection under specifications. The tests cannot be considered appropriate for engineering design in applications differing widely from the load-time scale of the standard test. Such applications may require additional tests, such as impact, creep, and fatigue.
Scope
1.1 This test method covers the determination of the mechanical properties of plastic lumber and plastic lumber shapes when loaded in shear at relatively low uniform rates of straining or loading.
1.2 Plastic lumber and plastic lumber shapes are currently made predominately with recycled plastics where the product is nonhomogenous in the cross section. However, this test method would also be applicable to similarly manufactured plastic products made from virgin resins or where the product is nonhomogenous in the cross section.
1.3 The values stated in inch-pound units are to be regarded as the standard. The SI units given in parentheses are for information only.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Note 1-There is no similar or equivalent ISO standard.