Short introduction –
ASTM standards are consensus standards for systems, services, materials and products. ‘ASTM International’ is one of the largest voluntary standard developing organization in the world. It is a non-profit organization that provides a forum for the development and publication of international voluntary standards. There are approximately 12,575 ASTM standards that operate globally.
TESTING ASTM STANDARDS-
There test methods help in the determining of the flexural properties of the reinforced plastics and the non- reinforced ones. This includes high-modulus composites and electrical insulating material which is shaped into a rectangular bar. However, these tests cannot be determined by the material …show more content…
The flexural properties may vary from materials to materials which usually depends on the way the specimen is prepared, the temperature of the surrounding and the depth of the specimen.
The ‘Apparatus’ required for the test are:- Testing machines, Micrometers loading noses and supports.
A testing machine is required which can be properly calibrated and can be separated at a constant rate of crosshead motion. The error in the load should not exceed more than -1% - +1% of the maximum load. Appropriate corrections should be made if the stiffness of the testing material exceed more than -1% - +1% of the maximum load.
Loading Noses and supports- In order to avoid excessive indurations or failure to stress concentration they must have cylindrical surfaces. The radii of the loading nose should be 5±1 mm unless specified or agreed upon between the interested clients.
If other sorts of loading Noses and supports are used the following conditions are required-
3.2mm or more in depth, radius should be 1.6 times the specimen depth, shall have 3.2 mm of the minimum radius, the arc of the loading nose should be sufficiently …show more content…
Z= gives us the straining of the outer fiber.
D= represents the depth of the beam.
Z should be equal to 0.01
A plate with parallel grooves can be used to check the parallelism of the apparatus. Loading nose and supports would fit when it is properly aligned.
A load has to be applied to the specimen at the specific crosshead rate and may take simultaneous load-deflection data. Secant modulus or tangent modulus of elasticity, chord and the flexural strength can be determines by the load-deflection curves. To correct the necessary seating and identification of the specimen perform the toe compensation.
When the maximum stain in the outer surface of the test specimen has reached to 0.05mm/mm the test should terminated or if the break occurs prior to achieve the maximum strain. The deflection can be calculated by-
D= midspan deflection, r= strain, L=support span, d=depth of the beam.
If the strain is beyond 5% the test is not applicable some other mechanical property might be more relevant.
The toe compensation adjustment must be made to determine the adequate calculated values of the