Intermittent carbon nanotube encapsulation of carbon fiber: A facile and efficient strategy to simultaneously strengthen and toughen interphase of composites

Conventional carbon fiber reinforced polymer composites are in urgent need to meet the increasing demand for simultaneously strong and tough to be applied as primary force-taking structure in extreme environment. The challenge remains to solve the contradiction between strength and toughness, since an increment in one is usually at the expense of the other. The prospect of interphase structure and properties tuning may be a good solution channel. Here, by constructing alternating sporadic and dense carbon nanotubes (CNTs) around cylindrical fiber via facile, eco-friendly and highly efficient vacuum filtration approach that enables us to gain a similar concave-convex structure, which leads to rough fiber surface and significantly improved wettability of fiber with polymer matrix. The resultant composites reveal respective 69.1% and 159% increase up to 102.5 MPa and 110.6 J/m2 in interfacial shear strength and toughness, greatly exceeding other composites modified by CNTs. The original and innovative strategy of intermittent CNTs encapsulation offers an avenue for obtaining high-performance composites for structural applications.