Glass-fibre-reinforced composites with enhanced mechanical and electrical properties - Benefits and limitations of a nanoparticle modified matrix

Nanoparticles and especially carbon nanotubes (CNTs) provide a high potential for the modification of polymers. They are very effective fillers regarding mechanical properties, especially toughness. Furthermore, they allow the implication of functional properties, which are connected to their electrical conductivity, into polymeric matrices. In the present paper, different nanoparticles, as fumed silica and carbon black, were used to optimise the epoxy matrix system of a glass-fibre-reinforced composite. Their nanometre-size enables their application as particle-reinforcement in FRI's produced by the resin-transfer-moulding method (RTM), without being filtered by the glass-fibre bundles. Additionally, an electrical field was applied during curing, in order to enhance orientation of the nanofillers in z-direction. The interlaminar shear strengths of the nanoparticle modified composites were significantly improved (+16%) by adding only 0.3 wt.% of CNTs. The interlaminar toughness G(Ic) and G(IIc) was not affected in a comparable manner. The laminates containing carbon nanotubes exhibited a relatively high electrical conductivity at very low filler contents, which allows the implication of functional properties, such as stress-strain monitoring and damage detection

Toughening mechanisms on recycled rubber modified epoxy based composites reinforced with graphene nanoplatelets

Recycling is a subject undergoing intense study in terms of sustainable development. In every area, recycling is strongly encouraged by governments due to the international agreements on environmental issues. For example, many industrial manufacturers have a tendency to find clean and cost-efficient solutions by utilizing recycled materials to produce new components. In this regard, rubbers have very wide usage in aeronautic and automotive industries both in structural and in interior body components. Rubbers are also used to modify brittle polymer components in the existence of hard, resistant fillers. In this study, fresh scrap EPDM rubbers are used to manufacture novel composites by modifying epoxy resin with the inclusion of graphene nano platelets (GnPs). Rather than micro sized particles, nanoparticles have high surface area, which means that a low content of these nanoparticles may enhance the material’s properties more efficiently. Besides, due to its superior structural, thermal and physical characteristics, addition of graphene promises improved mechanical properties if they can be dispersed homogeneously. This paper is focused on the fracture characteristics and toughening mechanisms of epoxy – fresh scrap rubber composites. The mechanical and physical properties of these composite systems are studied in the present work. Mechanical properties are examined by means of three-point bending tests with smooth and single edge notched beam specimens (SENB). Also, nano indentation tests were realized to see the creep compliance and viscoelastic properties. Finally, scanning electron microscope (SEM) was used to observe the fracture surfaces and the microstructure

Piezoresistive polypropylene-carbon nanofiber composites as mechanical transducers

Abstract: polymeric materials have been replacing other materials in various applications, from structural to electronic components. In particular, since the discovery of conducting polymers and the beginning of the manufacture of conducting composites with carbon fillers, their use in electronics is growing up. A group of electronic components with large potential for industrial applications such as structural monitoring, biomedical or robotics are sensors based on the piezoresistive effect, fabricated from conductive polymers and/or composites. The aim of this article is to characterize the piezoresistive effect of conductive polymer composites based on polypropylene filled with carbon nanofibers, and to demonstrate a way of fabricating strain gauges from these materials, using industrial techniques. With this purpose, some films were prepared by shear extrusion, which allows the composites to be produced industrially in a standard non-expensive process. Then, both the dependence of the electrical response on the preparation conditions and on the mechanical solicitations was measured. The obtained gauge factor values, up to 2.5, and piezoresistive coefficients up to 0.0019 mm2/N, prove the viability of these materials for fabricating strain-gauges, where their main advantages are the lower price and the ability to deal with much higher deformations, when compared to metal or semiconductor strain-gauges.We acknowledge the Foundation for Science and Technology through the 3 degrees Quadro Comunitario de Apoio, the POCTI and FEDER programs and the NANO/NMed-SD/0156/2007 project. The support of Applied Sciences Inc. for generously supplying the CNFs used. We would also like to thank Carla Leer and Patrick Lake for their assistance in the production of the CNF composites. J. G. Rocha thanks the FCT for the Grant SFRH/BSAB/1014/2010