ASTM C1773 provides information on the mechanical behavior and strength of CFCC tubes. This information is used for material development, material comparison, quality assurance, characterization, and design data generation.
CFCCs consist of a ceramic matrix reinforced by ceramic fibers in all directions (1D, 2D, and 3D). They remain stable at extreme temperatures. They are resistant to corrosion, wear, and damage. Therefore, they are suited for high-temperature structural applications.
ASTM C1773 applies primarily to advanced ceramic matrix composite tubes with continuous fiber reinforcement. And although this test method is not intended for discontinuous fiber-reinforced, whisker-reinforced, or particulate-reinforced ceramics, it can be equally applicable to these composites.
The mechanical properties of CFCC tubes cannot be predicted by applying measured properties from flat CFCC to the design of tubes. The CFCC tubes must be directly tested to provide reliable data.
This test is applicable only at ambient temperature. Elevated temperature testing requires furnaces and heating devices and temperature-capable grips and loading fixtures. These are not addressed in this test. The width of the gage section of the CFFC tube is measured. The thickness of the tube wall is measured. The test specimen is loaded on a fixture that holds it. The specimen/fixture assembly is then mounted monotonically in the testing machine in uniaxial tension. The applied tensile force and strain on the gage section are recorded. They are used to determine the mechanical behavior of CFCC tubes.
The axial tensile strength and the fracture strength are determined from the maximum applied force and the fracture force. The strains, the proportional limit stress, and the tensile modulus of elasticity will be determined from the stress-strain data.
Test specimens consist of CFCC tubes with outer diameters of 10 to 150 mm and wall thicknesses of 1 to 25 mm, where the ratio of the outer diameter-to-wall thickness is typically between 5 and 30.
Axial tensile strength:
Su = Pmax /A
Pmax = the maximum load
A = average shear stressed area, which is calculated as:
A = Wh
W = average specimen width, and
h = average distance between the notches
S f =Pbreak/A
S f= the tensile strength
Pbreak = the breaking load when the test specimen separates into two or more pieces.
Strain at Fracture Strength:
Strain at fracture strength is determined as the engineering strain corresponding to the fracture strength.
Modulus of Elasticity
Calculate the modulus of elasticity as follows:
E = /
E = modulus of elasticity, and
/ = the slope of the – curve within the linear region