Structuring the thermoplastic interleaf with lotus-leaf-like structure and its interlaminar toughening for CFRPs

Abstract

A new kind of self-supporting thermoplastic film with two-sided lotus-leaf-like structure was prepared and its effect on the interlaminar fracture toughness of carbon fiber/epoxy composite was studied. Phenolphthalein modified polyetherketone films with uniform, large scaled lotus-leaf-like structure were prepared by soft lithography. After interleaved with the structured films, the mode I interlaminar fracture toughness of the composite is slightly increased by 17%, whereas the mode II interlaminar fracture toughness is substantially increased as high as 325%. It is found that a special interlayer structure was formed, which contains thermoplastic nails and thermoplastic-rich layer. The mode I fracture path occurred mainly inside the carbon plies, whereas the mode II fracture path propagated through the highly tough thermoplastic nails and the thermoplastic-rich layer, and it frequently deflected near the thermoplastic nails, causing a high energy dissipation. This new method for preparing structured interleaves is expected to provide a new route for interlayer design.