Abstract
The effect of plasma treatment of the multi-walled carbon nanotube (MWCNT) surface on the fracture toughness of an aerospace grade epoxy resin and its unidirectional (UD) carbon fiber prepreg laminates has attracted scientific interest. A prepreg route eliminates the possible risk of carbon nanotube filtration by unidirectional carbon fibers. X-ray photoelectron spectroscopy results suggested that oxygen atom concentration at the nanotube surface was increased from 0.9% to 3.7% after plasma modification of the carbon nanotubes. A low number (up to 0.5 wt.%) of MWCNTs was added to epoxy resin and their carbon fiber prepreg laminates. Transmission electron micrographs revealed that the plasma treatment resulted in a better dispersion and distribution of MWCNTs in the epoxy resin. Plasma-treated MWCNTs resulted in a more pronounced resistance to the crack propagation of epoxy resin. During the production of the reference and nanotube-modified prepregs, a comparable prepreg quality was achieved. Neat nanotubes agglomerated strongly in the resin-rich regions of laminates lowering the interlaminar fracture toughness under mode I and mode II loading. However, plasma-treated nanotubes were found mostly as single particles in the resin-rich regions of laminates promoting higher energy dissipation during crack propagation via a CNT pull-out mechanism.
Highlights
Since the last decade, fiber-reinforced polymer composites have been increasingly used by the civil aircraft industry due to their high specific stiffness and strength, chemical resistance, and thermo-mechanical properties [1]
Carbon fiber prepregs impregnated with epoxy resins have especially been the material of choice for the primary structural composite parts
Plasma treatment led to an increase of oxygen atom concentration at the surface of multi-walled carbon nanotube (MWCNT)
Summary
Fiber-reinforced polymer composites have been increasingly used by the civil aircraft industry due to their high specific stiffness and strength, chemical resistance, and thermo-mechanical properties [1]. Carbon fiber prepregs impregnated with epoxy resins have especially been the material of choice for the primary structural composite parts. It is, well known that epoxy resins are generally brittle and possess low fracture toughness [2]. The toughening of epoxy resins has been widely investigated by incorporating various additives in matrix, such as core–shell [3], rubber [4], nano-silica [5], layered silicates [6,7], graphene [8], and single- or multi-walled carbon nanotubes [9,10,11]. A high number of parameters, including the dispersion and distribution quality of CNTs [15], or the nanotube length and aspect ratio [16] affect the nanocomposite morphology, and the final mechanical properties
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