Mechanical response and failure behavior of fiber enforced porous ceramics by directional freeze-casting

The objective of this research is to explore the correlation between the piezomagnetic response and ratcheting failure behavior under asymmetrical cyclic stressing in X80 pipeline steel. The magnetic field variations from cycle to cycle were recorded simultaneously during the whole-life ratcheting test. Analysis made in the present work shows that the piezomagnetic hysteresis loop evolves systematically with the number of cycles in terms of its shape and position. Corresponding to the three-stage process in the mechanical response, piezomagnetic response can also be divided into three principal stages, but the evolution of magnetic parameter is more complex. Furthermore, the loading branch and unloading branch of the magnetic field-stress hysteresis loop separate gradually from each other during ratcheting failure process, leading to the shape of hysteresis loop changes completely. Therefore, the progressive degradation of the steel under ratcheting can be tracked by following the evolution of the piezomagnetic field. And the shape transition of the hysteresis loop can be regarded as an early warning of the ratcheting failure.

Download Full-text

Radial-Concentric Freeze Casting Inspired by Porcupine Fish Spines

Ceramics ◽

10.3390/ceramics2010015 ◽

2019 ◽

Vol 2 (1) ◽

pp. 161-179 ◽

Cited By ~ 9

Author(s):

Frances Su ◽

Joyce Mok ◽

Joanna McKittrick

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Axial Compression ◽

Porous Ceramics ◽

Compressive Modulus ◽

Splitting Tensile Strength ◽

High Porosity ◽

Freeze Casting ◽

Casting Method ◽

Multiphase Materials

Freeze casting is a technique used to manufacture porous ceramics with aligned microstructures. In conventional freeze casting, these microstructures are aligned along a single direction of freezing. However, a caveat to these ceramics has been their ensuing lack of strength and toughness due to their high porosity, especially in the direction orthogonal to the direction of alignment. In this work, a novel freezing casting method referred to as “radial-concentric freeze casting” is presented, which takes its inspiration from the radially and concentrically aligned structure of the defensive spines of the porcupine fish. The method builds off the radial freeze casting method, in which the microstructure is aligned radially, and imposes a concentric alignment. Axial compression and Brazilian tests were performed to obtain axial compressive strengths, axial compressive moduli, and splitting tensile strengths of freeze cast samples with and without epoxy infiltration. Notably, radial-concentric freeze cast samples had the greatest improvements in axial compressive modulus and splitting tensile strength with infiltration, when compared against the changes in mechanical properties of conventional and radial freeze cast ceramics with infiltration. These results provide further evidence for the importance of structure in multiphase materials and the possibility of enhancing mechanical properties through the controlled alignment of microstructures.

Download Full-text

Properties of Highly Filled, Highly Plasticized, Semicrystalline Polymer Networks

Rubber Chemistry and Technology ◽

10.5254/1.3538551 ◽

1991 ◽

Vol 64 (2) ◽

pp. 181-201 ◽

Cited By ~ 2

Author(s):

Richard D. Vargo ◽

Frank N. Kelley

Keyword(s):

Tensile Strength ◽

Mechanical Response ◽

Polymer Networks ◽

Three Dimensional ◽

Important Variable ◽

Failure Behavior ◽

Energy Data ◽

Viscoelastic Effects ◽

Tearing Energy ◽

Increasing Temperature

Abstract 1. Component reactivity of ingredients such as fillers and plasticizers is significant and is measurable by a technique developed during this work. 2. The undesirable syneresis problem common to these highly plasticized materials can be controlled through adjusting equivalence ratios. Syneresis can be controlled primarily by decreasing the crystallinity of the material. 3. Changing percent crystallinity with temperature is a very important variable controlling the physical properties, i.e., ultimate properties, tearing energy, and dynamic-mechanical response. 4. The tearing energy data did not display simple amorphous behavior, and, as such, could not be shifted using a reduced variables technique such as WLF shifting. All variables were needed to represent the data. Three dimensional plotting developed previously by von Merrwall et al. was utilized to represent the data. The resulting tear-energy data exhibit the normal viscoelastic effects of rate and temperature as well as the superposition of the effects of crystallinity on the tearing energy. A decrease in tearing energy with increasing temperature is primarily due to increasing crystallinity in the samples. Plasticizer decreased the tearing energy, while filler increased the tearing energy. Filler lessened the effects of temperature and plasticizer on tearing energy. 5. Ultimate property measurements using ring samples for these model propellants revealed that these materials did not behave in a simple thermo-rheological manner, since crystallinity effects are predominant in the tensile mode. Because of crystallinity and strain-induced crystallinity, the data could not be represented by a failure envelope as proposed by Smith. The presence of plasticizer has the effect of decreasing the tensile strength, while filler tends to increase the tensile strength for the plasticized systems. 6. A model is presented to explain the high strain-to-failure behavior of these systems. Further details of this work can be found in Reference 22.

Download Full-text

Freeze-Casting of Porous Ceramics: A Review of Current Achievements and Issues

Advanced Engineering Materials ◽

10.1002/adem.200700270 ◽

2008 ◽

Vol 10 (3) ◽

pp. 155-169 ◽

Cited By ~ 723

Author(s):

S. Deville

Keyword(s):

Porous Ceramics ◽

Freeze Casting

Download Full-text

A Structurally Based Stress-Stretch Relationship for Tendon and Ligament

Journal of Biomechanical Engineering ◽

10.1115/1.2798284 ◽

1997 ◽

Vol 119 (4) ◽

pp. 392-399 ◽

Cited By ~ 127

Author(s):

C. Hurschler ◽

B. Loitz-Ramage ◽

R. Vanderby

Keyword(s):

Distribution Function ◽

Probability Distribution ◽

Failure Criterion ◽

Probability Distribution Function ◽

Mechanical Response ◽

Elastic Fiber ◽

Tissue Level ◽

Constitutive Law ◽

Failure Behavior ◽

Simplified Form

We propose a mechanical model for tendon or ligament stress–stretch behavior that includes both microstructural and tissue level aspects of the structural hierarchy in its formulation. At the microstructural scale, a constitutive law for collagen fibers is derived based on a strain-energy formulation. The three-dimensional orientation and deformation of the collagen fibrils that aggregate to form fibers are taken into consideration. Fibril orientation is represented by a probability distribution function that is axisymmetric with respect to the fiber. Fiber deformation is assumed to be incompressible and axisymmetric. The matrix is assumed to contribute to stress only through a constant hydrostatic pressure term. At the tissue level, an average stress versus stretch relation is computed by assuming a statistical distribution for fiber straightening during tissue loading. Fiber straightening stretch is assumed to be distributed according to a Weibull probability distribution function. The resulting comprehensive stress–stretch law includes seven parameters, which represent structural and microstructural organization, fibril elasticity, as well as a failure criterion. The failure criterion is stretch based. It is applied at the fibril level for disorganized tissues but can be applied more simply at a fiber level for well-organized tissues with effectively parallel fibrils. The influence of these seven parameters on tissue stress–stretch response is discussed and a simplified form of the model is shown to characterize the nonlinear experimentally determined response of healing medial collateral ligaments. In addition, microstructural fibril organizational data (Frank et al., 1991, 1992) are used to demonstrate how fibril organization affects material stiffness according to the formulation. A simplified form, assuming a linearly elastic fiber stress versus stretch relationship, is shown to be useful for quantifying experimentally determined nonlinear toe-in and failure behavior of tendons and ligaments. We believe this ligament and tendon stress–stretch law can be useful in the elucidation of the complex relationships between collagen structure, fibril elasticity, and mechanical response.

Download Full-text

Freeze casting of aqueous coal fly ash/alumina slurries for preparation of porous ceramics

Journal of Physics and Chemistry of Solids ◽

10.1016/j.jpcs.2009.12.022 ◽

2010 ◽

Vol 71 (4) ◽

pp. 503-506 ◽

Cited By ~ 10

Author(s):

Hyung Bin Ji ◽

Won Young Kim ◽

Tae Young Yang ◽

Seog Young Yoon ◽

Byung Kyu Kim ◽

...

Keyword(s):

Fly Ash ◽

Coal Fly Ash ◽

Porous Ceramics ◽

Freeze Casting

Download Full-text

Preparation, Microstructure and Properties of ZrO2 Gradient Porous Ceramics by Freeze-Casting Process

Materials Science Forum ◽

10.4028/www.scientific.net/msf.816.226 ◽

2015 ◽

Vol 816 ◽

pp. 226-230 ◽

Cited By ~ 2

Author(s):

Tao Tao Ai

Keyword(s):

Electron Microscopy ◽

Compressive Strength ◽

Porous Structure ◽

Cross Section ◽

Lamellar Structure ◽

Sintering Temperature ◽

Casting Process ◽

Porous Ceramics ◽

Freeze Casting ◽

Scanning Electron

The ZrO2gradient porous ceramics were prepared by a novel freeze-casting process. The porous structure of the ZrO2ceramics was investigated by scanning electron microscopy (SEM). And the porosity and compressive strength were also measured. Experimental results indicated that the porous structure of the specimens was remarkably affected by the sintering temperature. The dendritic pores were obtained after sintered at 1300 °C. The porosity and compressive strength of the specimen were 56.79% and 4.37 MPa, respectively. As the sintering temperature reached to 1500 °C, a lamellar structure was obtained on the cross-section of the specimen. Meanwhile, the porosity decreased to 26.77% and the compressive strength increased to 8.26 MPa. The ceramics can be divided subsequently into three distinctive zones along the solidification direction, i.e. lamellar zone, transition zone and cellular zone.

Download Full-text

Micromechanical Modeling of Damage Evolution and Mechanical Behaviors of CF/Al Composites under Transverse and Longitudinal Tensile Loadings

Materials ◽

10.3390/ma12193133 ◽

2019 ◽

Vol 12 (19) ◽

pp. 3133

Author(s):

Zhenjun Wang ◽

Siyuan Yang ◽

Zehui Du ◽

Wugui Jiang ◽

Aodi Zhang ◽

...

Keyword(s):

Mechanical Response ◽

Matrix Alloy ◽

Fracture Morphology ◽

Micromechanical Modeling ◽

Interface Debonding ◽

Failure Behavior ◽

Transverse Fracture ◽

Fiber Failure ◽

Transverse Tensile ◽

Alloy Properties

This paper investigates the progressive damage and failure behavior of unidirectional graphite fiber-reinforced aluminum composites (CF/Al composites) under transverse and longitudinal tensile loadings. Micromechanical finite element analyses are carried out using different assumptions regarding fiber, matrix alloy, and interface properties. The validity of these numerical analyses is examined by comparing the predicted stress-strain curves with the experimental data measured under transverse and longitudinal tensile loadings. Assuming a perfect interface, the transverse tensile strength is overestimated by more than 180% and the transverse fracture induced by fiber failure is unrealistic based on the experimental observations. In fact, the simulation and experiment results indicate that the interface debonding arising from the matrix alloy failure dominates the transverse fracture, and the influence of matrix alloy properties on the mechanical behavior is inconspicuous. In the case of longitudinal tensile testing, however, the characteristic of interface bonding has no significant effect on the macroscopic mechanical response due to the low in-situ strength of the fibers. It is demonstrated that ultimate longitudinal fracture is mainly controlled by fiber failure mechanisms, which is confirmed by the fracture morphology of the tensile samples.

Download Full-text