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The resin characterization is a key element in the manufacturing of composite materials. Resin processing properties and their associated constitutive models are essential in order to define and optimize the processing parameters and predict the final properties of a composite structure. In this article, a comprehensive methodology is presented to characterize the main processing properties of a thermoset resin system. As a case study, the thermal, chemorheological, and thermomechanical properties of the CYCOM 890RTM epoxy resin were investigated. A cure kinetics model taking into account the diffusion was found to accurately predict resin cure kinetics behavior within the processing condition range. The developed resin rheological model accurately predicted the onset of resin gelation and the evolution of resin viscosity with temperature and degree-of-cure. The glass transition temperature and instantaneous elastic modulus were determined using also a rheometer in a solid torsion mode. Finally, volumetric changes, resin chemical shrinkage and coefficient of thermal expansion were investigated taking into account the chemical and thermal effects. In general, the detailed procedure and techniques presented in this work can be applied to the intensive characterization of a wide range of thermoset resin systems.

Carbon nanotubes (CNT) in their various forms have great potential for use in the development of multifunctional multiscale laminated composites due to their unique geometry and properties. Recent advancements in the development of CNT hierarchical composites have mostly focused on multi-walled carbon nanotubes (MWCNT). In this work, single-walled carbon nanotubes (SWCNT) were used to develop nano-modified carbon fiber/epoxy laminates. A functionalization technique based on reduced SWCNT was employed to improve dispersion and epoxy resin-nanotube interaction. A commercial prepregging unit was then used to impregnate unidirectional carbon fiber tape with a modified epoxy system containing 0.1 wt% functionalized SWCNT. Impact and compression-after-impact (CAI) tests, Mode I interlaminar fracture toughness and Mode II interlaminar fracture toughness tests were performed on laminates with and without SWCNT. It was found that incorporation of 0.1 wt% of SWCNT resulted in a 5% reduction of the area of impact damage, a 3.5% increase in CAI strength, a 13% increase in Mode I fracture toughness, and 28% increase in Mode II interlaminar fracture toughness. A comparison between the results of this work and literature results on MWCNT-modified laminated composites suggests that SWCNT, at similar loadings, are more effective in enhancing the mechanical performance of traditional laminated composites.Crown

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