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

Continuous carbon fiber-toughened ZrB2-based composites (Cf/ZrB2-based composites) are potential thermostructural 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 Cf/ZrB2- based composite (Cf/PDC/ZrB2). 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 Cf/PDC/ZrB2 composite. PDC can effectively modulate the interface of Cf/ZrB2-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 Cf/PDC/ZrB2 composite was 8.4 MPa center dot m1/2, representing a 19 % enhancement in comparison with the composite without a PDC layer. The work of fracture of Cf/PDC/ZrB2 composite was 8.5 kJ center dot m 2, significantly surpassing that of the composite without a PDC layer (1.7 kJ center dot 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/pullout.