This work explores the development of a scalable process to manufacture nanomaterial enhanced fibre reinforced thermoplastic composites. The high specific strength and stiffness properties of carbon fibre reinforced composites (CFRPs) are of value to aerospace, automotive, energy and sporting industry. Polyether ether ketone (PEEK), is a high performance aerospace thermoplastic with a high melting temperature, strength and chemical resistance properties. However, intrinsic electrical and thermal conductivity properties of PEEK are not sufficient for electrical and thermal dissipation applications without further enhancement. Incorporation of highly conductive nanomaterials offers an effective approach to enhancing thermal and electrical properties of CFRPs.
The methods to synthesise high-quality nanomaterials are generally not scalable or cost-effective. Liquid phase exfoliation (LPE) offers a scalable method to generating high quality, purity nanomaterials at low cost. High concentration aqueous nanomaterial suspensions stabilised using non-ionic surfactants are environmentally and industrially beneficial. Development of a high concentration aqueous graphene and boron nitride nanosheet (BNNS) suspensions with F108 and F68 surfactant were investigated. The liquid nanosuspensions were spray deposited onto CF/PEEK prepreg tape substrates to develop thin films for interlaminar enhancement. The thin film surface roughness and nanomaterial quality were characterised with respect to the increased nanomaterial additions, surfactant content and polymer chain length properties.
With increased nanomaterial loadings the surfactant content increased resulting in reduced anisotropic thermal, electrical and mechanical properties exhibited by the nanocomposite. Micro-computed tomography techniques imaged long cylindrical voids concentrated within the nanomaterial interlayers and permeating the entire nanocomposite. Numerical simulations of void locations were in agreement with the measured anisotropic electrical and thermal property reductions.
Optimisation of the methodology found that a shorter surfactant chain, reduced surfactant content in the suspension formulation and heat treatment of the thin films and composite substrates had a strong correlation with reduced void content. The electrical and thermal property enhancements of the manufactured graphene nanocomposites were measured in addition to significant mechanical improvements. Preliminary anisotropic improvements were observed with BNNS additions using the same methodology. The optimised methodology successfully demonstrated scalable manufacture of thermally and electrically conductive CF/PEEK composites with nanomaterial interlayer additions.