A First Principle Study of Mechanical Strength of Kevlar-29

The first principle study is performed for the analysis of the mechanical strength of Kevlar-29. The structure is optimized by the density functional theory implemented in SIESTA. The bond strength is investigated by the displacement of central nitrogen atom along X, Y and Z directions; respectively. The structural property analysis provides an asymmetric nature of Kevlar-29. Larger bond breaking energy is observed during compression along Z direction and vice versa for elongation. There is strong s-p hybridization in the orbitals and exhibits an insulating nature. The forbidden energy gap is increased while compression and it reduces gradually during elongation. The bonds have higher ionic and lower covalent nature, there is larger covalency for applied strain along Z-axis, hence the strength is little higher along the same axis than along X and Y-axes. Larger stress is required along Z-axis to produce the strain and smaller along Y-axis, therefore; Kevlar-29 is mechanically stronger along its Z-axis and weaker along Y-axis.