ASTM C1468 Test for Transthickness Tensile Strength of Advanced Ceramics

Scope:

ASTM C1468 is used for material development, material comparison, quality assurance, characterization, and design data generation of CFCCs. 

This test is used for Advanced Ceramic Composites with continuous fiber reinforcement: unidirectional (1D), bidirectional (2D), woven, and tridirectional (3D). This test can also be used with glass matrix composites with 1D, 2D, and 3D continuous fiber reinforcement. 

3D architectures with a high volume fraction of fibers in the z-axis are difficult to test with this method. Although this test is not intended for discontinuous fiber-reinforced, whisker-reinforced, or particulate-reinforced ceramics, it can be equally applicable to these composites. 

Test Procedure:

In ASTM C1468 test procedure, specimens with different grip interfaces and specimen geometry are mounted differently in the load train. The dimensions of the specimens are determined. The test modes and rates to be used for specific specimens are determined. 

The test mode and test rate are selected on the test machine. The load cell is adjusted to zero with one of the fixtures mounted on the load cell. The fixture is removed and the test specimen is inserted. The specimen is preloaded to remove the “slack” from the load train, and the amount of preload used is reported. The amount of preload for each situation is specific to each material’s tensile test specimen geometry. For ASTM C1468, the preload should be less than 1 % of the expected failure load. 

The data acquisition and test mode are initiated. The specimen is fractured, and the action of the test machine is disabled. The data collection of the data acquisition system is disabled. The breaking load is measured and recorded. The specimen is carefully removed from the grip interfaces. The specimen halves are placed along with other fragments from the gauge section into a suitable, non-metallic container for later analysis. 

 Specimen size:

In ASTM C1468, a round or square specimen is tested for tensile strength in the direction normal to the thickness. Test specimens should have a dimension of 10 mm at least. Test specimens that are circular and have a  diameter of 19 mm provide better results when compared to other geometries having a similar cross-sectional area. 

Data:

The following data is calculated in ASTM C1468 testing:

Engineering Stress:

σ =P/A

σ = the engineering stress,
P = the applied, uniaxial tensile load, and
A = the original cross-sectional area.

Transthickness Tensile Strength:

S_u = P_max /A

Su = The transthickness tensile strength, and
Pmax = The breaking load in units of N.

Modulus of Elasticity:

E = ∆σ/ ∆€

E = modulus of elasticity, and
∆σ/ ∆€ = the slope of the σ – € curve within the linear region

Conclusion:

ASTM C1468 is used to determine Transthickness Tensile Strength of Continuous Fiber-reinforced Ceramic Composites (CFCC) under monotonic uniaxial loading at ambient temperature.