Enhanced fracture properties of continuous Cf/ZrB2-based composites with polydopamine-derived carbon boundary layer

Continuous carbon fiber-toughened ZrB 2 -based composites (C f /ZrB 2 -based composites) are potential thermo-structural materials suitable for ultra-high temperature applications. To improve the fracture properties, polydopamine-derived carbon (PDC) was deposited on carbon fibers and used as a boundary layer of C f /ZrB 2 -based composite (C f /PDC/ZrB 2 ). Results indicated that PDC was applied uniformly to fibers, with no instances of cross-sticking observed among adjacent fibers. The matrix could effectively infiltrate into the intra-bundle region, resulting in the formation of a highly dense C f /PDC/ZrB 2 composite. PDC can effectively modulate the interface of C f /ZrB 2 -based composite. Using polydopamine-derived carbon (PDC) as a boundary layer, the average interfacial shear strength of the composite was decreased from 369 MPa to 133 MPa. The fracture toughness of C f /PDC/ZrB 2 composite was 8.4 MPa·m 1/2 , representing a 19 % enhancement in comparison with the composite without a PDC layer. The work of fracture of C f /PDC/ZrB 2 composite was 8.5 kJ·m −2 , significantly surpassing that of the composite without a PDC layer (1.7 kJ·m −2 ). The outstanding fracture properties can be attributed to the beneficial interfacial bonding established by PDC layer between fiber and matrix, which promotes the activation of toughening mechanisms including crack branching/deflection and fiber bridging/pull-out.