ASTM C1819-21 PDF

SIGNIFICANCE AND USE 5.1 This test method (also known as overhung tube method) may be used for material development, material comparison, material screening, material down selection, and quality assurance. This test method is not recommended for material characterization, design data generation, material model verification/validation, or combinations thereof. 5.2 Continuous fiber-reinforced ceramic composites (CFCCs) are composed of continuous ceramic-fiber directional (1D, 2D, and 3D) reinforcements in a fine-grain-sized ( 5.3 CFCC components have a distinctive and synergistic combination of material properties, interface coatings, porosity control, composite architecture (1D, 2D, and 3D), and geometric shape that are generally inseparable. Prediction of the mechanical performance of CFCC tubes (particularly with braid and 3D weave architectures) cannot be made by applying measured properties from flat CFCC plates to the design of tubes. In particular, tubular components comprised of CMCs material form a unique synergistic combination of material and geometric shape that are generally inseparable. In other words, prediction of mechanical performance of CMC tubes generally cannot be made by using properties measured from flat plates. Strength tests of internally pressurized CMC tubes provide information on mechanical behavior and strength for a multiaxially stressed material. 5.4 Unlike monolithic advanced ceramics which fracture catastrophically from a single dominant flaw, CMCs generally experience “graceful” fracture from a cumulative damage process. Therefore, while the volume of material subjected to a uniform hoop tensile stress for a single uniformly pressurized tube test may be a significant factor for determining matrix cracking stress, this same volume may not be as significant a factor in determining the ultimate strength of a CMC. However, the probabilistic nature of the strength distributions of the brittle matrices of CMCs requires a statistically significant numb... SCOPE 1.1 This test method covers the determination of the hoop tensile strength including stress-strain response of continuous fiber-reinforced advanced ceramic tubes subjected to an internal pressure produced by the expansion of an elastomeric insert undergoing monotonic uniaxial loading at ambient temperature. This type of test configuration is sometimes referred to as an overhung tube. This test method is specific to tube geometries because flaw populations, fiber architecture, and specimen geometry factors are often distinctly different in composite tubes, as compared to flat plates. 1.2 In the test method a composite tube/cylinder with a defined gage section and a known wall thickness is loaded via internal pressurization from the radial expansion of an elastomeric insert (located midway inside the tube) that is longitudinally compressed from either end by pushrods. The elastomeric insert expands under the uniaxial compressive loading of the pushrods and exerts a uniform radial pressure on the inside of the tube. The resulting hoop stress-strain response of the composite tube is recorded until failure of the tube. The hoop tensile strength and the hoop fracture strength are determined from the resulting maximum pressure and the pressure at fracture, respectively. The hoop tensile strains, the hoop proportional limit stress, and the modulus of elasticity in the hoop direction are determined from the stress-strain data. Note that hoop tensile strength as used in this test method refers to the tensile strength in the hoop direction from the induced pressure of a monotonic, uniaxially loaded elastomeric insert, where “monotonic” refers to a continuous, nonstop test rate without reversals from test initiation to final fracture. 1.3 This test method applies primarily to advanced ceramic matrix composite tubes with continuous fiber reinforcement: unidirectional (1D, filament wound and tape lay-up), bidirectional (2D, fabr...