Bolsa de Doutoramento FCT: Graphene-based composite laminates for structural applications [UI/BD/151477/2021]

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CFRP laminates enhanced with graphene nanoparticles in multifunctional applications

Publication . Parente, J.M.; Carvalho, Ana; Nunes-Pereira, João; Reis, Paulo; Pereira Silva, A

In automobile, aeronautical, aerospace, sports and energy fields, there has been an increase of the use of carbon fibre reinforced polymers (CFRP) due their considerable advantages, such as, low weight, static and fatigue strength as well as corrosion resistance1. The addition of nanoparticles, in particular carbon allotropes, like graphene nanoplatelets (GNP) or carbon nanotubes (CNT) allow not only enhanced mechanical performance2, but also can alter the electrical conductivity response of the CFRP composite system3. While the carbon fibre is conductive, the epoxy is not conductive, and the aleatory dispersion of the nanoparticles should introduce in the composite system considerable changes in electric conductivity. The present work intends to study the effect of GNP on the mechanical response of composite laminates, and for this purpose CFRP laminates with and without GNP were manufactured and characterized in terms of flexural and viscoelastic behaviour. Furthermore, electric conductivity tests were performed to investigate the influence of the GNP in the electric response. The results obtained, show that the addition of GNP amounts up to 0.75 wt. % to the epoxy matrix improved the flexural results (Figure 1a). Concerning the electromechanical properties, it was possible to conclude that both laminate composites, with and without GNP, presented reproducible piezoresistive response, with a negative relative change in resistance (ΔR/R0) with increasing strain (), which may allow the health monitoring of the structure (Figure 1b).

2023Documento de conferência

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Graphene-based composite laminates for structural applications

Publication . Parente, João Miguel Nunes; Reis, Paulo Nobre Balbis dos; Silva, Abílio Manuel Pereira da; Pereira, João Pedro Nunes

This thesis explores the synthesis, microstructure and properties of polymer-matrix composites reinforced with graphene nanoplatelets (GNP), carbon nanotubes (CNT) and carbon nanofibers (CNF), both as individual fillers and in hybrid combinations. The aim is to develop structural materials with high mechanical performance and integrated self-sensing capabilities. Nanocomposites were produced by dispersing nanoparticles in epoxy resin, followed by thermal curing. Mechanical and sensing behaviour were evaluated using three-point bending and cyclic fatigue tests under realistic loading conditions. Viscosity measurements show that GNP or CNF can increase resin viscosity by up to 74 %, which challenges processing at higher loadings. Curing at 5 °C yields the best flexural strength and surface hardness, with GNP-reinforced composites showing up to 24.8 % strength improvement. Volumetric shrinkage during cure varies with filler type: GNP increases shrinkage by 91 %, while CNF reduces it by 77 %, underscoring the role of nanoparticle–matrix interactions. In fibre-reinforced laminates, placing glass fibres on the compression side of hybrid carbon/glass layups enhances both load and deflection at peak, with a 3G/5C configuration achieving a 5.9 % higher peak force and 13.1 % greater deflection than the reverse. Incorporating 0.75 wt. % GNP into carbon-fibre laminates raises bending stiffness and extends fatigue life by 15.1 %, while increases of 10.6 % and 9.2 % are observed in hybrid and glass-fibre laminates. These enhancements show that even low graphene concentrations effectively delay fatigue damage. Combining CNT and GNP at equal loadings (0.375 wt. % each) yields synergistic gains in stiffness and strength. In carbon-fibre composites, strength and stiffness rise by 11 % and 18 %, respectively; glass-fibre composites show gains of 8 % and 55 %. Electrical resistance monitoring during fatigue reveals gauge factors up to three times those of commercial strain gauges, with stress-amplitude sensitivity improving by 20.1 % in carbon composites and 32.4 % in glass composites. This confirms high-sensitivity and stable self-sensing. The integration of hybrid nanofillers with mechanical and electrical performance validation forms a framework for designing multifunctional composites. Key challenges remain in scaling uniform nanoparticle dispersion, ensuring long-term network stability and standardizing sensor calibration. Addressing these issues is essential for translating laboratory results into practical Structural Health Monitoring (SHM) applications.

2026-03-27Tese de doutoramento

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Entidade financiadora

Fundação para a Ciência e a Tecnologia

Programa de financiamento

OE
Bolsa de Doutoramento

Número da atribuição

UI/BD/151477/2021