Scope:

ASTM D7291 standard test is designed to measure the through-thickness flatwise tensile strength and elastic modulus of fiber-reinforced polymer matrix composite materials using the universal testing machine and a fixture. The maximum amount of tensile stress that a material can take until failure is termed tensile strength. Similarly, the slope of the strain-strain curve in the elastic deformation area is called elastic modulus. This test is usually employed for circular samples and focuses on maintaining alignment while bonding the fixture blocks to the sample. The material forms are bound to only continuous-fiber or discontinuous fiber (tape type or 2-dimensional fabric or both) reinforced composites.

Test Procedure:

A universal testing machine and a fixture having three dissimilar parts are formulated as specified by ASTM D7291 standard. The test sample is prepared as per the standard. The sample diameter is measured at three different locations. Then, the average diameter is calculated and recorded. The end tabs are bonded to the sample and mounted into the fixture. It is ensured that the long axis of the sample and end tab assembly is aligned with the test direction. A strain gauge is applied to the sample to measure the modulus of elasticity. Also, a tensile force is applied at a constant crosshead displacement rate as per the standard. The force vs crosshead displacement data is determined and recorded. The strain data are noted in case strain gauges are used. The maximum force and the displacement or strain are recorded at the instant of failure to test the sample’s failure. 

Sample size:

The sample might be in the shape of a straight-sided cylindrical disk or a reduced gauge section cylindrical spool. The diameter of the sample should be 1 inch (25 mm). 

Data:

Through-Thickness Modulus of Elasticity

Ultimate Flatwise Through-Thickness Tensile Strength