ASTM C1863 Test for Hoop Tensile Strength of Advanced Ceramic Tube Using Direct Pressurization

Scope:

ASTM C1863 determines the ability of a CFCC tube to withstand internal pressure. It is also known as the tube burst test because a pressurized fluid applies pressure to the inner walls until the tube bursts. 

This test method is used for material development, material comparison, material screening, material down selection, and quality assurance. It is also used for material characterization, design data generation, and material model validation. 

The ASTM C1863 test method is used primarily to test CFCC tubes with continuous fiber reinforcement. CFCCs are essentially ceramic matrices reinforced by fibers. The ceramic matrix and the fiber reinforcement each can be made from a wide range of materials: oxide, graphite, carbide, nitride, and other compositions. Although this test method is not intended for discontinuous fiber-reinforced, whisker-reinforced, or particulate-reinforced ceramics, it may be equally applicable to these composites.

Test Procedure:

For ASTM C1863 testing, the dimension of the composite tube is measured including its wall thickness. The composite tube is loaded by internal pressurization from a pressurized fluid. Internal pressure is exerted on the tube by the fluid. The pressure is applied either directly to the material or through a secondary bladder inserted into the tube. The pressure is monotonic (unchanging). This radial pressure on the inside of the tube results in a hoop stress-strain response. The pressure is applied until the tube bursts.

The hoop tensile strength is determined from the resulting maximum pressure and the hoop fracture strength is determined from the pressure at fracture. The stress-strain data recorded in the ASTM C1863 testing, is used to determine hoop tensile strain, the hoop proportional limit stress, and the modulus of elasticity in the hoop direction. 

 Specimen size:

As per ASTM C1863, the geometry of the tubular test specimen depends on the ultimate use of the hoop tensile strength data. Minimum five test specimens are required for estimating a mean. More may be necessary if estimates regarding the form of the strength distribution are required. Fewer tests can be conducted for an indication of material properties if material cost or test specimen availability limits the number of possible tests.

Data:

The following data is calculated in ASTM C1863 testing:

Internal Pressure:

p = F/π(r_i^tube)²

p = internal pressure
F = axial force required by the tubular test specimen
r_i^tube = internal diameter of tube units of mm

Hoop Tensile Stress:

σ _h= η _mpX2(rt_i^tube)²/(r₀^tube)² – (rt_i^tube)²

σ _h = hoop tensile stress
P = internal pressure
η _m = maximum stress factor
r_i^tube = inner radius of the tube
r₀^tube = outer radius of the tube

Hoop Tensile Strain:

ɛ _h= 2 ∆r/2r₀^tube

ɛ _h = hoop tensile strain
∆r = change in radius
r₀^tube = outer radius of the tube

Hoop Tensile Strength:

S_hu= η _mp_maxX2(rt_i^tube)²/[(r₀^tube)² – (rt_i^tube)²]

S_hu = hoop tensile strength
p_max = maximum internal pressure
η _m = maximum stress factor
r_i^tube = inner radius of the tube
r₀^tube = outer radius of the tube

Hoop Tensile Fracture Strength:

S_hf= η _mp_fX 2(rt_i^tube)²/[(r₀^tube)² – (rt_i^tube)²]

S_hf = hoop tensile fracture
p_max = internal pressure at fracture
η _m = maximum stress factor
r_i^tube = inner radius of the tube
r₀^tube = outer radius of the tube

Modulus of Elasticity:

E=∆σ_h/ ∆ɛ_h

E = modulus of elasticity,
∆σ_h/ ∆ɛ_h = the slope of the (σ_h– ε_h) curve within the linear region.

Poisson’s Ratio:

v=- ɛ_l/ ɛ_h

ν = Poisson’s ratio
ɛ_l/ ɛ_h = the slope of the linear region of the plot of longitudinal strain versus hoop strain

Conclusion:

ASTM C1863 is used to determine the hoop tensile strength, including stress-strain response, of continuous fiber-reinforced advanced ceramic (CFCC) tubes subjected to direct internal pressurization applied monotonically at ambient temperature.