Quantitative in-situ study of strength-governed interfacial failure between h-BN and polymer-derived ceramic

To quantitatively study the toughening behavior in two-dimensional (2D) material reinforced ceramics, pull-out experiments were conducted to investigate the properties of the interface between multi-layer h-BN nanosheet and polymer-derived ceramic (PDC). By using nanoindentation-assisted micro-mechanical devices integrated with scanning electron microscopy (SEM), the interfacial sliding and failure behaviors between h-BN and PDC were systematically studied. The failure process was monitored in situ with precise quantitative measurements of the relative displacements across the interface that were obtained with digital image correlation (DIC). An analytical cohesive shear-lag model was developed, and the interfacial modulus and strength of the h-BN/PDC interface were measured to be 5.65 ± 1 GPa⋅µm⁻¹ and 66.4 ± 16.8 MPa, respectively. A micromechanical analysis shows that the interfacial failure in these materials is governed by the interfacial strength at small length scales, rather than the interfacial fracture energy.