ASTM D790-15 pdf free.Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials.
These test methods are used to determine the flexural properties of unreinforced and reinforced plastics, including highmodulus composites and electrical insulating materials utilizing a three-point loading system to apply a load to simply supported beam (specimen). The method is generally applicable to both rigid and semi-rigid materials, but flexural strength cannot be determined for those materials that do not break or that do not fail yield in the outer surface of the test specimen within the 5.0 % strain limit.
4. Summary of Test Method
4.1 A test specimen of rectangular cross section rests on two supports in a flat-wise position and is loaded by nieans of a loading nose located midway between the supports. Unless testing certain laminated materials (see 7 for guidance), a support span-to-depth (of specimen) ratio 16:1 shall he used. The specimen is deflected until rupture occurs in the outer surface of the test specimen or until a maximum strain (see 5.1.6) of 5.0 % is reached, whichever occurs first.
4.2 Procedure A is designed principally for materials that break at coitiparatively small delkctions amid it shall be used [or measurement of flexural properties, particularly flexural modulus, unless the material specification states otherwise. Procedure A employs a strain rate of 0.01 mm/mm/mm (0.0 1 in./in./min) and is the preferred procedure for this test method.
4.3 Procedure B is designed principally for those materials that do not break or yield in the outer surface of the test specimen within the 5.0 % strain limit when Procedure A conditions are used. of these test methods and it shall be used for measurement of ilexural strength only. Proccure B employs a strain rate of 0.10 mm/rnnilmin (0.10 in./in./min). Procedure B employs a strain rate of 0.10 mm/mm/mm (0.10 in./in./min).
7. Test Specimens
7. 1 Test specimens that are cut from plates, or
molded or extruded shapes, or molded to the ired finished
dimensions are acceptable. The actual dimensions used shall be measured in accordance with Test Methods D5947. The depth of the specimen shall be defined as the thickness of the material. The depth shall not exceed the width (see Note 11). The crosssection of the specimens shall be rectangular with opposite sides flat and parallel and adjacent sides perpendicular along the full length of the specimen
7. 2 Whenever possible, the original surface of the sheet shall be unaltered. However, where testing machine limitations make it impossible to follow the above criterion on the unaltered sheet. one or both surfaces shall be machined to provide the desired dimensions, and the location of the specimens with reference to the total depth shall be noted Consequently, any specifications for flexural properties on thicker sheets must state whether the original surfaces are to be etained or not. When only one surface was machined, it must be stated whether the machined surface was on the tension or compression side of the beam. Any necessary polishing of specimens shall be done only in the lengthwise direction of the specimen.ASTM D790-15 pdf free download.