Interfacial Stabilities, Electronic Properties and Interfacial Fracture Mechanism of 6H-SiC Reinforced Copper Matrix Studied by the First Principles Method

The interfacial mechanics and electrical properties of SiC reinforced copper matrix composites were studied via the first principles method. The work of adhesion (Wad) and the interfacial energies were calculated to evaluate the stabilities of the SiC/Cu interfacial models. The carbon terminated (CT)-SiC/Cu interfaces were predicted to be more stable than those of the silicon terminated (ST)-SiC/Cu from the results of the Wad and interfacial energies. The interfacial electron properties of SiC/Cu were studied via charge density distribution, charge density difference, electron localized functions and partial density of the state. Covalent C-Cu bonds were formed based on the results of electron properties, which further explained the fact that the interfaces of the CT-SiC/Cu are more stable than those of the ST-SiC/Cu. The interfacial mechanics of the SiC/Cu were investigated via the interfacial fracture toughness and ultimate tensile stress, and the results indicate that both CT- and ST-SiC/Cu interfaces are hard to fracture. The ultimate tensile stress of the CT-SiC/Cu is nearly 23 GPa, which is smaller than those of the ST-SiC/Cu of 25 GPa. The strains corresponding to their ultimate tensile stresses of the CT- and ST-SiC/Cu are about 0.28 and 0.26, respectively. The higher strains of CT-SiC/Cu indicate their stronger plastic properties on the interfaces of the composites.

Interfacial Stabilities, Electronic Properties and Interfacial Fracture Mechanism of 6H-SiC Reinforced Copper Matrix studied by the First Principles Method

The interfacial mechanics and electrical properties of the SiC reinforced copper matrix composites were studied via the first principles method. The work of adhesion (Wad) and the interfacial energies were calculated to evaluate the stabilities of the SiC/Cu interfacial models. The carbon terminated (CT)-SiC/Cu interfaces were predicted more stable than those of the silicon terminated (ST)-SiC/Cu from the results of the Wad and interfacial energies. The interfacial electron properties of SiC/Cu were studied via the charge density distribution, charge density difference, electron localized functions and partial density of the state. The covalent C-Cu bonds were formed based on the results of the electron properties, which further explained the fact that the interfaces of the CT-SiC/Cu are stable than those of the ST-SiC/Cu. The interfacial mechanics of the SiC/Cu were investigated via the interfacial fracture toughness and ultimate tensile stress, and the results indicate that both CT- and ST-SiC/Cu interfaces are hard to fracture. The ultimate tensile stress of the CT-SiC/Cu is nearly 23GPa, which is smaller than those of the ST-SiC/Cu of 25 GPa. The strains corresponding to their ultimate tensile stresses of the CT- and ST-SiC/Cu are about 0.28 and 0.26, respectively. The higher strains of CT-SiC/Cu indicate their stronger plastic properties on the interfaces of the composites.

A RAPID METHOD FOR RELIABILITY ANALYSIS OF COMPOSITE TOPHAT STIFFENED STRUCTURES USING A FIRST PRINCIPLES METHOD AND DESIGN RULES

Composite materials are increasingly being used within engineering, especially in low weight applications. A significant drawback that these materials exhibit is their variability. There is a growing trend towards stochastic analysis of marine structures and this is even more important for scenarios that have a high variability. To implement these new techniques it is important to be able to, rapidly and accurately, determine reliability during the design phase. Therefore, a reliability analysis, utilising a rapid implementation, has been performed on plates that have been designed using two different sets of design rules and a first principles method. The results show that whilst, under the limits investigated, the reliability of the design rules are slightly safer than those found using first principles; the sensitivity analysis shows that each of the design rules generates a different reaction from each variable, encouraging different types of structures through their idiosyncrasies. Furthermore the method shown allows a rapid analysis to be performed on complex composite structures in a relatively short time frame using either first principles methods or design rules.

An Investigation of the Mechanism on Interfacial Charge Transformation of the TiB2/Cu Composites Studied by the First Principles

The charge communications have been widely existed in the metal materials when they are under the processing, the modeling and the failing. We studied the interfacial charge transformation of the TiB2/Cu composites via the first principles method. The layer thickness was predicted by the interfacial charge communications performed on the regions of the TiB2/Cu interfaces. The layer thickness of the Ti-terminated (TT)TiB2/Cu were predicted longer than those of the B-terminated(BT) TiB2/Cu and contrasting with their average vales as 0.75 (nm) and 0.65 (nm), respectively. The Mulliken population was applied to investigate the bond length, bond population and charge transformation of the six TiB2/Cu models. The Ti-Cu bond was only detected in TT-HCP interfaces among the all TT-TiB2/Cu models, which was further confirmed that the metallic bond of the Ti-Cu with the bond length and population as 2.5 Å and 0.22, respectively. Nevertheless, the B-Cu bond were detected in all BT-TiB2/Cu models, and the bond length and population higher than those of B-Cu bond in chemical complexes. The 5 atomic layers were involved in quantitative analyses of the interfacial charge transformation. The results indicate that the charges lost by interfacial Ti atom were inequivalent obtained by Cu and B atoms which nearby the interfacial Ti atoms of the TT-TiB2/Cu. Comparing with the BT-TiB2/Cu models, the charges acquired by the interfacial B atom were most from the Ti and less from the Cu atoms surrounded the interfacial B atoms.

Mechanical and Electronic Properties of DNTF Crystals under Different Pressure

In the present study, the effects of pressure on the structure, elastic properties and electronic structure of DNTF compounds are studied using the first principles method. It is found that pressure has a great influence on lattice constants. When the pressure reaches 80 GPa, the structure of DNTF changes suddenly. The variation trend of C11, C22 and C33 values is consistent with that of pressure. In addition, pressure can improve the compressibility and shear resistance of the DNTF compound. The pressure can reduce the bandgap and further increases the charge density, causing DNTF to decompose and explode.