Abstract
In this work, the carbon fibres (CFs) surfaces were modified via sizing and coated with a very thin layer of a complex formulation including carbon nanotubes (CNTs). A push-out method was developed based on nanoindentation to assess the interfacial shear strength of the fibre/matrix. The mechanical properties such as indentation hardness, reduced modulus, indentation displacement and indentation creep of the composite were evaluated by means of the Oliver-Pharr method. The critical load of different composites was measured and the interfacial shear strength (IFSS) was calculated to compare the effect of the CNTs concentration in the sizing solution. Wettability evaluation of the sized fibres was performed prior to nanoindentation to investigate the adhesion of the resin. After push-out testing, characterisation by optical microscopy/SEM was carried out to ratify the results. It was found sizing with a small amount of evenly distributed nano-inclusion on CFs can increase the interfacial shear strength but large amount of sizing could lead to a decrease of the interfacial bonding due to the agglomeration of CNTs on CFs.
Highlights
A carbon fibre reinforced polymer (CFRP) composite consists of a continuous matrix which helps to keep the shape and carbon fibres (CFs) distributed within it to ensure the strength of materials
CFs surfaces were modified with a very thin layer via sizing by a complex formulation including different amounts of carbon nanotubes (CNTs), which aims at creating strong interfaces between the fibre and the matrix in the composite
A push-out method based on nanoindentation was used to measure the critical load, and to calculate the interfacial shear strength (IFSS) to compare the effect of the varied sizing amount of CNTs
Summary
A carbon fibre reinforced polymer (CFRP) composite consists of a continuous matrix (resin) which helps to keep the shape and CFs distributed within it to ensure the strength of materials. Sizing was used to treat CFs by dispersing CNTs in agents of water-borne polycarbonate (WPC) and water-borne polyurethane (WPU) It was found small content of CNTs addition has a beneficial effect on the bonding between CF (CF) and polycarbonate (PC) [10]. The average interfacial shear strength (IFSS) at the fibre/matrix interface can be calculated by the critical load, the sheet thickness and the fibre diameter [14]. The interfacial properties of sized CFs by CNTs and epoxy resin were investigated using the instrumental nano-indentation machine. The mechanical properties such as indentation hardness, reduced modulus, indentation displacement and indentation creep of the composite were evaluated by means of the OliverPharr method [15]. Characterisations by OM/SEM were carried out to ratify the results
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