University of Saskatchewan,
Keywords: fracture mechanics, SiC/Cu, interpenetrating phase nanocomposites, molecular dynamics
Summary:Owing to their high strength, good abrasion resistance, low density, high melting temperature, and other interesting characteristics, ceramics have been extensively used in a wide range of industries . However, one of the major drawbacks of the ceramics is low fracture toughness. To address this issue, several studies have been conducted. One of the very effective means is using ceramics along with a second ductile phase to address this issue. This is a new class of composites with three dimensional, interconnected microstructural networks of the constituents was introduced which are referred to as interpenetrating phase composites (IPCs) or co-continuous composites. With advancement in manufacturing at the nano scale, it is now vital to have an in-depth understanding of the effective mechanisms and behavior of IPCs at that scale [2,3]. In the present study, the effect of various parameters on the fracture behavior of SiC at atomic scale is studied by using molecular dynamics (MD) method. The parameters such as crack orientation, temperature, strain rate, presence of a Cu (as a ductile phase), and the volume fraction of the Cu are studied. The presence of Cu phases is found to be very effective method for increasing the ductility of ceramics even at low volume fractions of Cu. However, the efficacy of Cu phase fades out as the temperature increases. Three low-index crack surfaces including (110), (111), and (100) in crystalline 3C-SiC are investigated and it is found that the fracture energy and crack growth direction is totally dependent on the crack orientation and the crack propagation could be totally different for different planes of crack. In order to investigate how the mentioned factors would affect the development of dislocation, plastic deformation, and amorphization, a visual methodology was employed. In this method, different results such as atomic stress field, atomistic local von Mises shear strain invariant, coordination number and central symmetry parameter are being plotted on the atomic model and different colors are allocated to different values, thus the location of presence of damage or plasticity can be easily detected. It is found that the visualization method can be a very effective method for detecting different types of dislocations (see Fig. 1). Moreover, the toughness of SiC under different conditions were calculated and utilized as a quantitative means for comparing the effect of different factors.