Strength and Toughness of Network Materials

A Computational investigation of local material strength and toughness on crack growth

A cracking approach to inventing new tough materials: fracture stranger than friction.

Specific application method for determining the strength and fracture toughness of metal materials

A new methodology inspired from the Theory of Critical Distances for determination of inherent tensile strength and fracture toughness of rock materials

Paper-based friction materials have been used for power train in vehicles. The motional property and reliability of vehicles depend on the mechanical properties and strength of paper-based friction materials. Paper-based friction materials are composed of aramid fiber, cellulose fiber, carbon fiber, fillers and resin, and have an extremely complex microstructure. The mechanical properties and strength of paper-based friction materials are affected by constituent materials and a fabrication method. Their effects on the mechanical properties and strength are not fully investigated In addition, an experimental method to evaluate the mechanical properties and strength of paper-based friction materials has not been established. In this study, effects of fibers on in-plane tensile strength and debonding fracture toughness of paper-based friction materials were investigated. Experimental results show that the aramid fibers reduces the in-plane tensile strength but enhances the debonding fracture toughness, the cellulose fibers enhance the in-plane tensile strength but reduces the debonding fracture toughness and the carbon fibers reduces the in-plane tensile strength and the debonding fracture toughness.

This paper is concerned with the diffraction problem in a transversely isotropic piezoelectric medium by a half-plane. The half-plane obstacle considered here is a semi-infinite slit, or a crack; both its surfaces are traction free and electric absorbent screens. In a generalized sense, we are dealing with the Sommerfeld problem in a piezoelectric medium.¶The coupled diffraction fields between acoustic wave and electric wave are excited by both incident acoustic wave as well as incident electric wave; and the sound soft and electric "blackness" conditions on the screens are characterized by a system of simultaneous Wiener-Hopf equations. Closed form solutions are sought by employing special techniques. Some interesting results have been obtained, such as mode conversions between acoustic wave and electric wave, novel diffraction patterns in the scattering fields, and the effect of electroacoustic head wave, as well as of surface wave-Bleustein-Gulyaev wave.¶Unlike the classical Sommerfeld problem, in which the only concern is the scattering field of electric wave, the strength of material, e.g. material toughness, is another concern here. From this perspective, relevant dynamic field intensity factors at the crack tip are derived explicitly.

By means of different checks and measures, we observed and analysed the microstructure of Fe−Al/Al2O3 composite material. We found that not only intragranular nanostructure grains and rod-like crystals but also fine-grained structure of the composite material as well as the bridging of the Fe−Al intermetallics compound contribute to the material's strength and toughness. It is shown that the strengthening and toughening of the Fe−Al/Al2O3 composite is the joint effect of a multiplicate strengthening and toughening mechanism.

With the rapid development of the polymer materials industry and the improvement of people's environmental awareness, magnesium hydroxide has been widely used in polymer materials due to its high decomposition temperature, non-toxic smoke suppression, and the advantages of neutralizing harmful gases produced by polymer combustion. However, the conventional preparation methods of magnesium hydroxide exhibit several issues, including high hydrophilicity, elevated polarity, and limited compatibility with polymers. This research proposes an improved method by adding sodium stearate and KH560 modifier, controlling the rate of magnesium oxide and preparing magnesium hydroxide flame retardants using a modifier-directed hydration method. Various characterizations confirmed its morphology, particle size and structure. The magnesium hydroxide exhibits low polarity, small particle size, stable structure and excellent hydrophobicity (with a contact angle of 120.32°, and a free energy of 1.34mN/m). In parallel, the magnesium hydroxide/polypropylene composites demonstrate excellent flame retardancy (LOI of 25%, V-1 grade) and simultaneously enhance the dispersion of magnesium hydroxide within the polypropylene matrix, improving the material's toughness and strength.

The fragmentation of a brittle plate subjected to dynamic biaxial loading is investigated via numerical simulations. The aim is to extend our understanding of the dynamic processes affecting fragment size distributions. A scalable computational framework based on a hybrid cohesive zone model description of fracture and a discontinuous Galerkin formulation is employed. This enables large-scale simulations and, thus, the consideration of rich distributions of defects, as well as an accurate account of the role of stress waves. We study the dependence of the fragmentation response on defect distribution, material properties, and strain rate. A scaling law describing the dependence of fragment size on the parameters is proposed. It is found that fragmentation exhibits two distinct regimes depending on the loading rate and material defect distribution: one controlled by material strength and the other one by material toughness. At low strain rates, fragmentation is controlled by defects, whereas at high strain rates energy balance arguments dominate the fragmentation response.

Effects of Immobilization on the Biomechanical Properties of the Broiler Tibia and Gastrocnemius Tendon

A method of strength evaluation based on fracture mechanics is important to analyze the fracture strength of material with crack. The heterogeneity of mechanical property in dissimilar materials causes change of fracture behavior. Analysis of mechanical property and fracture strength in dissimilar materials is important to evaluate fracture toughness with accuracy. The purpose of this paper is experimentally to analyze correlation between Young's modulus ratio and fracture toughness in dissimilar materials with a single edge crack. 4 kinds of specimen were used in this experiment. One was homogeneous material, the others were 3 kinds of dissimilar materials. The fracture behavior of dissimilar materials was analyzed by high-speed video camera and digital image correlation method. Then, specimens were bended and displacement near the crack was measured. Fracture toughness was experimentally calculated based on fracture mechanics. The experimental results showed that fracture energy and strain distribution around a crack tip were same values at all specimens. We conclude that relationship between Young's modulus ratio and fracture toughness in dissimilar materials is uncorrelated. Then, the heterogeneity of Young's modulus causes the change of crack opening displacement.

The uniaxial tensile properties of multi-scale fiber-reinforced cementitious material (MSFRCM) with steel and polyvinyl alcohol (PVA) fibers and calcium carbonate whisker (CW) were studied. The results showed that CW improved the uniaxial tensile stiffness, strength, peak strain, and toughness of the steel-PVA hybrid fiber-reinforced cementitious material. The CW not only played a role in the small deformation stage but also improved the load holding capacity and toughness of the hybrid fiber-reinforced cementitious material during the large deformation stage. Computational models to assess the uniaxial tensile strength and toughness of the MSFRCM were established. Microstructure observations showed that the steel and PVA fibers formed a weak interfacial transition zone (ITZ) due to the “wall effect.” The CW effectively optimized the structure of the ITZ of the steel and PVA fibers through physical and chemical effects, such as filling, bridging, improving Ca(OH)2 orientation, and chemical effects. The steel fibers, PVA fibers, and CW in the MSFRCM bridged cracks at the macro, mesoscopic, and microscopic levels, respectively. As a result, we observed a fiber chain effect that improved the positive hybrid effect between the multi-scale fibers.

The garbage issue becomes a very serious problem at the moment. Much research has been done to make waste into useful materials. One of the utilization of waste is as the basic material of composite material that can be applied in the field of engineering. Some of the wastes generated are styrofoam, bagasse and eggshell. Styrofoam, bagasse and eggshell can be applied to a composite material. Styrofoam serves as a composite binder material while the bagasse and eggshells serve as a reinforcement. Volume fraction between styrofoam, bagasse and eggshell are 80%:10%:10%, 70%:15%:15%, 60%:20%:20%, and 50%:25%:25%. The aims of research are determine the mechanical properties of composite material based waste materials from styrofoam, bagasse and eggshell. Mechanical properties tested in this study are bending strength and toughness of composite materials. The results showed bending strength of composite for each volume fraction of 80%:10%:10%, 70%:15%:15%, 60%:20%:20%, and 50%:25%:25% are 5.07 MPa, 8.45 MPa, 8.68 MPa, and 11.01 MPa, respectively. Toughness of composite materials for each volume fraction of 80%:10%:10%, 70%:15%:15%, 60%:20%:20%, and 50%:25%:25% are 0.33 J/mm2, 0.42 J/mm2, 0.75 J/mm2, and 0.75 J/mm2, respectively. Composite materials based on waste materials from styrofoam, bagasse and eggshell can be used as an alternative material for drone frames.

The influence of temper shape on the mechanical properties of archaeological ceramics

ABSTRACTThe influence of temperature between R.T. and liquid nitrogen (−196°C) on the strength and toughness of three grades of Mg-PSZ and a 3 mol% Y-TZP material have been investigated. The toughness of the Mg-PSZ materials passes through a maximum at the Ms temperature, whereas the strength increases monotonically with decreasing temperature regardless of Ms. The Y-TZP material exhibits increasing toughness with decreasing temperature but the strength passes through a maximum at -80°C. The results are discussed in terms of transformation and R-curve limited strength of transformation toughened ceramics. For Mg-PSZ materials it is suggested that the critical stress to initiate a non reversible transformation on the tensile surface is responsible for microcracking and ensueing R-curve development.