ASTM C1359 Test for Tensile Strength of Advanced Ceramics at Elevated Temperatures

Scope:

ASTM C1359 test method is primarily used for advanced ceramic matrix composites with continuous fiber reinforcement, which can be unidirectional (1D), bidirectional (2D), and tridirectional (3D), or other multi-directional reinforcements. It can also be used for glass matrix composites with 1D, 2D, 3D, and other multi-directional continuous fiber reinforcements. Although this test method does not directly address discontinuous fiber-reinforced, whisker-reinforced, or particulate-reinforced ceramics. This test method can be equally applicable to these composites.

Test Procedure:

ASTM C1359 test is performed as follows-

1) The specimen is mounted: Specimens with different grip interfaces and specimen geometry are mounted differently in the load train. 

2) Preparations for Testing:  The test mode and test rate are selected on the test machine. The specimen is preloaded to remove the “slack” from the load train, and the amount of preload used is reported. If possible the specimen is heated near-zero loads in the load control test mode. 

The extensometer is mounted. Depending on the extensometer, it is mounted on the specimen either at the ambient temperature or at elevated temperatures. At the ambient temperature, it is mounted on the specimen gauge section at zero output. The specimen is enclosed in the furnace and the refractory insulation is lightly packed to seal the specimen and the furnace. The specimen is heated to the test temperature at the prescribed rate until it reaches thermal equilibrium. When the specimen has reached thermal equilibrium, the extensometer is zeroed again. 

In ASTM C1359 testing, if the extensometer is to be mounted to a hot specimen, the specimen enclosed in the furnace and refractory insulation is lightly packed to seal the specimen and furnace. The specimen is heated to the test temperature at the prescribed rate and until the specimen has reached the desired temperature. The extensometer is mounted on the specimen gauge section at zero output. When the specimen has reached thermal equilibrium, the extensometer is zeroed again. 

3) Conducting the Test: If the test temperature is not being recorded continuously, the test temperature is recorded at test initiation. The data acquisition and the test mode are initiated. After specimen fracture, the test machine and the data collection of the data acquisition system are disabled. 

ASTM C1359 testing requires the breaking load to be recorded with an accuracy of 1.0% of the load range. The test temperature at test completion is recorded. The specimen and apparatus are cooled to the ambient temperature. The specimen is removed from the grip interfaces. The specimen along with any fragments from the gauge section is placed into a suitable, non-metallic container for later analysis. The ambient temperature and relative humidity are determined. 

 Specimen size:

A minimum of five specimens are required in ASTM C1359 testing for estimating the mean. More specimens are used for estimating the form of the strength distribution. 

Data:

The following data is calculated in ASTM C1359 testing:

1. Engineering Stress:

σ=P/A

σ = the engineering stress,
P = the applied, uniaxial tensile load.
A = the original cross-sectional area, mm2.

2. Engineering Strain:

€ = (I – I₀) I₀

ε = the engineering strain,
I = the extensometer gauge length at any time, and
I₀ = the original gauge length of the extensometer.

3. Tensile strength:

S_u = P_max /A

S_u = the tensile strength
P_max = the maximum load

4. Fracture Strength:

S _f =P_break/A

S_f= the fracture strength
P_break = the breaking load when the test specimen separates into two or more pieces.

5. Strain at Fracture Strength:

Strain at fracture strength is determined as the engineering strain corresponding to the fracture strength.

6. Modulus of Elasticity:

Calculate the modulus of elasticity as follows:

E = Δσ/ Δ €

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

Conclusion:

ASTM C1359 is used to determine the tensile strength, including stress-strain behavior, under monotonic uniaxial loading of continuous fiber-reinforced advanced ceramics (CFCC) at elevated temperatures.