Search

This study comprehensively investigates Al2O3′s mechanical properties, focusing on fracture toughness, surface energy, Young's modulus, and crack propagation. The density functional theory (DFT) is employed to model the vacancies in Al2O3, providing essential insights into this material's structural stability and defect formation. The DFT simulations reveal a deep understanding of vacancy-related properties and their impact on mechanical behavior. In conjunction with molecular dynamics (MD) simulations, the fracture toughness and crack propagation in Al2O3 are explored, offering valuable information on material strength and durability. The surface energy of Al2O3 is also assessed using DFT, shedding light on its interactions with the surrounding environment. The results of this investigation highlight the significant impact of oxygen vacancies on mechanical characteristics such as ultimate strength and fracture toughness, drawing comparisons with the effects observed in the presence of aluminum vacancies. Additionally, the research underscores the validation of fracture toughness outcomes derived from both DFT and MD simulations, which align well with findings from established experimental studies. Additionally, the research underscores the validation of fracture toughness outcomes derived from DFT and MD simulations, aligning well with findings from established experimental studies. The combination of DFT and MD simulations provides a robust framework for a comprehensive understanding of Al2O3′s mechanical properties, with implications for material science and engineering applications. [ABSTRACT FROM AUTHOR]

A density functional theory (DFT) calculation is carried out in this work to investigate the effect of vacancies on the behavior of Al(111)/6H SiC composites. Generally, DFT simulations with appropriate interface models can be an acceptable alternative to experimental methods. We developed two modes for Al/SiC superlattices: C-terminated and Si-terminated interface configurations. C and Si vacancies reduce interfacial adhesion near the interface, while Al vacancies have little effect. Supercells are stretched vertically along the z-direction to obtain tensile strength. Stress–strain diagrams illustrate that the tensile properties of the composite can be improved by the presence of a vacancy, particularly on the SiC side, compared to a composite without a vacancy. Determining the interfacial fracture toughness plays a pivotal role in evaluating the resistance of materials to failure. The fracture toughness of Al/SiC is calculated using the first principal calculations in this paper. Young's modulus (E) and surface energy (Ɣ) is calculated to obtain the fracture toughness (KIC). Young's modulus is higher for C-terminated configurations than for Si-terminated configurations. Surface energy plays a dominant role in determining the fracture toughness process. Finally, to better understand the electronic properties of this system, the density of states (DOS) is calculated. [ABSTRACT FROM AUTHOR]

The most frequently used construction material in buildings is concrete exhibiting a brittle behaviour. Adding fibers to concrete can improve its ductility and mechanical properties. To this end, a laboratory study was conducted to present an experimental model for the specimens' size effect of on macro-synthetic fiber-reinforced concrete using variations in fracture energy. Composite concrete beams with different thicknesses and widths were made and tested under mode I to obtain (1) fracture toughness, (2) fracture energy, and (3) critical stress intensity factor values. Results indicated that by increasing the thickness and the width, fracture toughness and fracture energy were enhanced. Moreover, increasing the thickness and width of the beam led to critical stress intensity factors enhancement respectively by 35.01–41.43% and 7.77–8.09%. [ABSTRACT FROM AUTHOR]

Fracture toughness, bending strength, Young's modulus, hardness and subcritical crack growth were determined for six different alumina/zirconia composites. The bending strength was modelled using Weibull distribution. The fracture toughness, bending strength and resistance to subcritical crack growth increase as a function of ZrO 2 content (stabilized with 3 mol% Y 2 O 3). The authors claim that a threshold stress in a three-parameter Weibull distribution may correspond to a threshold stress intensity factor in which the subcritical crack growth is negligible. [ABSTRACT FROM AUTHOR]

Polyurethane foams crush in compression and have a brittle fracture in tension, so their failure could be evaluated based on Linear Elastic Fracture Mechanics. Fracture toughness in mixed mode loading is of particular interest because foam cracking weakens the structure's capacity for carrying loads. Four fracture criteria (Maximum circumferential tensile stress, Minimum strain energy density, Maximum energy release rate, Equivalent stress intensity factor) were considered for evaluation of mixed mode fracture of three closed cell rigid polyurethane foams with densities: 100, 145 and 300 kg/m3. Mixed mode fracture tests were performed using asymmetric semi-circular specimen. The equivalent stress intensity factor criterion looks to give the better prediction of mixed mode fracture. Also the effect of cell orientation and the crack propagation angle were investigated. [ABSTRACT FROM AUTHOR]

Highlights: [•] Digital Image Correlation was used to measure R-curve of clay brick blocks. [•] DIC allows to collect data from crack propagation up to the total rupture of samples. [•] An average K IC of clay brick blocks equal to 0.36MPam1/2 was estimated. [•] A quite accurate R-curve of clay brick blocks was traced. [ABSTRACT FROM AUTHOR]

Many efforts have been made in recent years to determine the fracture toughness of different types of foams in static and dynamic loading conditions. Taking into account that there is no standard method for the experimental determination of the fracture toughness of plastic foams different procedures and specimens were used. This paper presents the polyurethane foam fracture toughness results obtained for different foam densities. Two types of specimens were used for determining fracture toughness in modes I, II and a mixed one, and also the size effect, loading speed and loading direction were investigated. The paper proposed correlations for density, cell orientation and mixed mode loading based on the experimental testing results. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents a correlation between dynamic and static fracture toughness of polyurethane rigid foams. Static three point bend tests and instrumented impact tests were performed using single edge notch specimens. The obtained results show that for all foam densities the dynamic fracture toughness is higher than the static toughness. Density appears to have the main influence on both static and dynamic fracture toughness. A quasi brittle fracture without plastic deformations and cushioning was observed for all foam densities. [Copyright &y& Elsevier]