Hybrid CFRP-CNT Micro-nanocomposites with Improved Fracture Toughness and Integrated Damage Sensing Capability.

Abstract

This thesis aims to utilize conductive carbon nanotube (CNT) networks in fibre reinforced plastics (FRPs) for integrated damage sensing functionalities. Different routes, including dissolvable thermoplastic carriers and direct spray coating techniques were employed for CNT delivery and localization in damage prone zones in composite laminates. Thermoplastic as well as thermoplastic/thermoset binary systems incorporating CNTs were studied, with a focus on electrical properties of the resulting nanocomposites and dissolution behaviour of the thermoplastic in the thermoset. Nanotube modified thermoplastic interleaves as well as direct CNT spray coating onto fibre preforms showed mechanical property improvement through increased interlaminar toughness. Percolated sprayed CNT networks have also been used as a sensitive tool for in-situ damage detection, and internal crack propagation during a standard composite test has been monitored by electrical sensing signals. Both interlaminar fracture toughness and interlaminar shear strength tests were performed in combination with in-situ damage sensing, and an excellent correlation between sensing signals and mechanical response was observed. These sensing signals have been used to determine internal crack propagation as well as damage levels during testing, with the potential for structural health monitoring.