Test for Tensile Strength of Advanced Ceramics at Elevated Temperatures ASTM C1359
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. ASTM C1359 is used for material development, material comparison, quality assurance, characterization, reliability assessment, and design data generation for CFCCs. The standard values are reported in SI units
This 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.
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 load control test mode.
Extensometer is mounted. Depending on the extensometer, it is mounted on the specimen either at ambient temperature or at elevated temperatures. At ambient temperature, it is mounted on the specimen gage section at zero output. The specimen is enclosed in the furnace and 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.
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 gage 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.
The breaking load is 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 ambient temperature. The specimen is removed from the grip interfaces. The specimen along with any fragments from the gage section is placed into a suitable, non-metallic container for later analysis. The ambient temperature and relative humidity are determined.
A minimum of five specimens is required for estimating the mean. More specimens are used for estimating the form of the strength distribution.
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 gage length at any time, and I0 = the original gage length of the extensometer.
3. Tensile strength:
Su = Pmax /A
Su = the tensile strength Pmax = the maximum load
4. Fracture Strength:
S f =Pbreak/A
Sf= the tensile strength Pbreak = 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