Types Of Fracture Behavior Research Articles

Fatigue fracture of hydrogels

Rapid advances are taking place to develop hydrogels of high stretchability and toughness, but fatigue fracture has not been studied for any hydrogels. This negligence hinders the development of hydrogels and their applications. Here we initiate a study of fatigue fracture of hydrogels. We choose polyacrylamide hydrogel as a model material. To place fatigue fracture in context, we apply monotonic, static, and cyclic load, and observe three types of fracture behavior: fast fracture, delayed fracture, and fatigue fracture. Below the critical load for fast fracture, we find two distinct thresholds, one for delayed fracture, and the other for fatigue fracture. The fracture behavior of hydrogel is sensitive to both the amplitude of load and the concentration of water. We relate the experimental observations to the molecular picture of swollen polymer networks. Fatigue fracture of hydrogels is a topic ready for scientific studies and engineering advances.

Influence of the Microstructure on the Fracture Behavior of Carbon Bonded Alumina

Carbon bonded alumina (Al2O3-C) in various compositions are developed for the production of open cell filters, which are used for melt metal filtration processes [. The Small Punch Test (SPT) is used to determine the mechanical properties of such materials. Previous investigations showed two different types of fracture behavior [2,, which can be distinguished by typical features of the load deflection curves of the SPT. This paper clarifies this behavior by examining the fracture surfaces using scanning electron microscopy (SEM).

평직 CFRP 적층복합재료의 섬유배열각도에 따른 파괴강도 예측

CFRP composite materials have been widely used in various fields of engineering because of their excellent properties. They show high specific stiffness and specific strength compared with metallic materiasl. Woven CFRP composite materials are fabricated from carbon fibers with two orientation angles (0°/90°), which influences the mechanical properties. Therefore, woven CFRP composite materials show different types of fracture behavior according to the load direction. Therefore, the fracture behavior of these materials needs to be evaluated according to the load direction when designing structures using these materials. In this study, we evaluate the fracture strength of plain-woven CFRP composite materials according to the load direction. We performed tests for six different angles (load direction: 0°/90°, 30°/-60°, +45°/-45°) and estimated the fracture strength for an arbitrary fiber angle by using the modified Tan's theory and harmonic function.

Acoustic Monitoring of Hydraulic Fracture Propagation in Pre-Fractured Natural Rocks

Active acoustic monitoring can capture two types of fracture behavior in rock samples, opening and closure of an existing fracture and tip movement of a propagating fracture. The first type is related to wave transmission across the fracture interface. The second one is related to the travel times of waves that diffract at the fracture tip. A series of experiment has been conducted with an acoustic system that has transducers mounted on the loading frames of a tri-axial cell situated in the Rock Mechanics Laboratory, TUDelft, the Netherlands. The existing fractures are formed by cleaving the rock samples into layers and putting them back together. The propagating fractures were created by hydraulic fracturing via bore-hole injection. The tests in this study featured both cleaved and hydraulic fractures, and aimed to characterize the interaction between them. This paper focus on the data processing that is adapted to these special tests and comparison between the monitored and recovered fractures.

Influence of molecular weight on impact fracture behavior of injection molded high density polyethylene: Scanning electron micrograph observations

AbstractA group of high density polyethylene with different molecular weight was prepared by melt blending two kinds of HDPE with weight average molecular weight of 3.2 × 105 g/mol and 7.2 × 105 g/mol, respectively. The fracture behavior of injection molded specimens of these samples was investigated by Izod impact test and scanning electron microscopy. The results show that the variations of impact toughness of injection molded HDPE could be reflected directly by the evolution of morphology of fracture surface as molecular weight increases. Higher molecular weight led to higher impact toughness, due to both thickened oriented shear zone which could enhance the crack resistance and depressed two types of fracture behavior (tearing‐brittle fracture and heat softening/melting fracture) with low energy consumption. Fracture behavior in different position of injection molded HDPE shows different molecular weight dependence. The impact toughness at far‐gate‐end increases with increasing molecular weight, while the impact toughness at near‐gate‐end, especially for the blends, almost keeps constant within a certain range of molecular weight. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Fracture behavior of cylindrical porous alumina with pore gradient

In this study, laminated cylindrical porous alumina materials with a pore gradient along the radial direction are fabricated by combining a lower sintering temperature with the presence of an organic-former (PMMA particles). It has been proved that pore morphology can be controlled by the lamination method in the centrifugal molding technique. The fracture behavior of the porous laminated alumina with a pore gradient is investigated by using the ring compression testing. An analytical formula to account for the pore gradient is introduced to calculate fracture strength based on the curved beam theory. There are two types of fracture behavior, which are not related to the lamination process and vary with the amount of pore-former. In the case of the same porosity, a reduction in fracture strength is observed with increase in the number of laminated layers, and the minimum strength is found in continuous graded cylinders.

Polyethylene toughened by CaCO 3 particles: The interface behaviour and fracture mechanism in high density polyethylene/CaCO 3 blends

Tensile behaviour and impact force-time curves of high density polyethylene/CaCO 3 blends have been investigated. The results showed that there may exist a flexible interfacial area with lower stiffness than the matrix. The concept of yielding in the interfacial area was proposed to explain the fracture mechanism of HDPE/CaCO 3 blends. Three types of fracture behaviour were assumed to be dependent on the surface-to-surface interparticle distance: (1) cavitation and crazing; (2) coexistence of cavitation and yielding in the interfacial area; (3) interfacial area yielding and matrix yielding. Based on the results, the interface conditions for brittle-ductile transition and core-shell morphology of CaCO 3 particles were discussed.

The analysis of interlaminar fracture in uniaxial fibre-polymer composites

One of the most important mechanical properties of a fibre-polymer composite is its resistance to delamination. The presence of delaminations may lead not only to complete fracture but even partial delaminations will lead to a loss of stiffness, which can be a very important design consideration. Because delamination may be regarded as crack propa­gation then an obvious scheme for characterizing this phenomenon has been via a fracture mechanics approach. There is, therefore, an extensive literature on the use of fracture mechanics to ascertain the interlaminar fracture energies, G c , for various fibre-polymer composites using different test geometries to yield mode I, mode II and mixed mode I/II values of G c . Nevertheless, problems of consistency and discussions on the accuracy of such results abound. This paper describes a detailed study of the methods of analysing the experimental data obtained from fracture mechanics tests using double-cantilever beam, end loaded split and end notched flexure specimens. It is shown that to get consistent and accurate values of G c it is necessary to consider aspects of the tests such as the end rotation and deflection of the crack tip, the effective shortening of the beam due to large displacements of the arms, and the stiffening of the beam due to the presence of the end blocks bonded to the specimens. Analytical methods for ascertaining the various correction constants and factors are described and are successfully applied to the results obtained from three different fibre-polymer composites. These composites exhibit different types of fracture behaviour and illustrate the wide range of effects that must be considered when values of the interlaminar fracture energies, free from artefacts from the test method and the analysis method, are required.

The effect of temperature on cold-rolled nylon-6

The effect of pre-orientation on nylon-6 at various temperatures reveals three types of fracture behaviour—(1) brittle (−196 and −150°C), (2) brittle/ductile (−100°C), and (3) ductile (above 100°C). Multiple fracture occurred in the brittle region, particularly with increasing degrees of pre-orientation. In the brittle/ductile transition region, there is evidence of ductility in the fractured specimen. Some evidence of flow is seen in the specimens pre-oriented up to 25%, but beyond that multiple fracture occurs although less marked than at the lower temperatures. In the third region, i.e. the ductile region, the material exhibits considerable ductility.