Liberata Guadagno

Effect of incorporation of carbon nanotubes on the mechanical properties of epoxy-amine composites

In this work, the effect of incorporation of multi-wall carbon nanotubes (MWCNTs) on the dynamic mechanical properties of epoxy-amine composites for structural applications was investigated. The composites were prepared by dispersing MWCNTs into an epoxy resin based on TetraGlycidyl-MethyleneDiAniline (TGMDA) and both epoxy precursor and composite were cured with 4,4-diamino diphenyl sulfone (DDS). Morphological investigation by atomic force microscopy (AFM) indicates efficient dispersion of MWCNTs in the thermosetting matrix. The dynamic mechanical properties show very high values in the storage modulus and glass transition temperature. The incorporation of MWCNTs induces an increase in the storage modulus and a change in the curve profile of tg δ suggesting a small fraction with lower mobility due to a different degree of crosslinking. A more effective curing cycle allows to compensate this drawback due to the inclusion of nanofiller inside epoxy matrix.

Healing efficiency of epoxy-based materials for structural application

This paper describes a self-healing composite exhibiting high levels of healing efficiency under working conditions typical of aeronautic applications. The self-healing material is composed of a thermosetting epoxy matrix in which a catalyst of Ring Opening Metathesis Polymerization (ROMP) and nanocapsules are dispersed. The nanocapsules contain a monomer able to polymerize via ROMP. The preliminary results demonstrate an efficient self-repair function which is also active at very low temperatures.

Anisotropic thermal conductivity study of nano-additives/epoxy based nanocomposites

This study investigates the anisotropic thermal conductivity behavior of an tetrafunctional epoxy resin containing low percentages (at loading level from 0.25 to 2% wt) of different types of carbon...

Thermal Degradation and fire properties of epoxy modified resins

The flammability of the resin is a major limitation in the aeronautic applications where new developed materials for primary and secondary structures must fulfill special regulation in order to demonstrate that their level of fire safety is equivalent to a conventional transport (aluminum) material. In this paper, the attention is focused on the thermal properties and the fire behavior of TGMDA based epoxy resins in which carbon nanotubes and POSS have been dispersed at nanometric or molecular level. The effect of the hardener, the diluent and the nanoparticles on the thermal properties has been investigated. Thermogravimetric data have been modeled according to the Coats and Redfen equations which provide a fast method for the determination of the kinetics of thermal degradation of polymers. The char yield has been used as criteria for evaluating limiting oxygen index (LOI) of the resin in accordance with Van Krevelen and Hoftyzer equation and the results have been compared with the experimental LOI dataThe flammability of the resin is a major limitation in the aeronautic applications where new developed materials for primary and secondary structures must fulfill special regulation in order to demonstrate that their level of fire safety is equivalent to a conventional transport (aluminum) material. In this paper, the attention is focused on the thermal properties and the fire behavior of TGMDA based epoxy resins in which carbon nanotubes and POSS have been dispersed at nanometric or molecular level. The effect of the hardener, the diluent and the nanoparticles on the thermal properties has been investigated. Thermogravimetric data have been modeled according to the Coats and Redfen equations which provide a fast method for the determination of the kinetics of thermal degradation of polymers. The char yield has been used as criteria for evaluating limiting oxygen index (LOI) of the resin in accordance with Van Krevelen and Hoftyzer equation and the results have been compared with the experimental LOI data

Manufacturing process of a multifunctional composite panel with nanocharged matrix

This paper proposes an effective manufacturing process developed to overcome drawbacks that can occur using a nanofilled resin as matrix in aeronautical composites. Nanoparticles embedded in epoxy resins impregnating carbon fibers are able to improve a composite with new desired functionalities. As soon as the nanoparticles are dispersed in a resin, the viscosity dizzily rises and usually, the traditional manufacturing processes are not suitable to obtain a good quality of the manufactured panels. An alternative method has been developed starting from the Resin Film Infusion (RFI) process. This method has been firstly tested on several flat panels, and then it has been transferred on a more complex shaped panel with three stringers. In this work, a flame resistant resin based on a tetrafunctional epoxy precursor filled with carbon nanotubes to increase electrical conductivity, has been used for the panel manufacturing.

Use of graphene oxide functionalized with Grubbs and Hoveyda Grubbs catalyst to activate metathesis reaction in epoxy mixtures

In this paper we discuss the possibility to use graphite oxide functionalized with Grubbs and Hoveyda Grubbs catalysts to activate metathesis reactions in epoxy mixtures.

Thermal conductivity of epoxy nanocomposites filled with MWCNT and hydrotalcite clay: A preliminary study

Aim of this work is to study the effect clay on the thermal conductivity of epoxy resin filled with CNTs. Experiments and theoretical predictions show that the presence of hydrotalcite clay in a mesh of carbon nanotubes gives rise to aggregates and twisted bundles, resulting in a lower carbon nanotubes length and a lower thermal conductivity of epoxy nanocomposites.

Synthesis of a new hardener agent for self-healing epoxy resins

Actually, the development of smart composites capable of self-repair in aeronautical structures is still at the planning stage owing to complex issues to overcome. One of the critical points in the development of self-healing epoxy resin is related to the impossibility to employ primary amines as hardeners. In this paper, the synthesis of a new hardener for self-healing resins is shown together with applicability conditions/ranges.

Use of FTIR Analysis to Control the Self-Healing Functionality of Epoxy Resins

In recent years polymer composites are increasingly used to replace the traditional metal alloys in structural applications, ranging from civil infrastructure to high performance vehicles such as racing cars and military aircraft. This popularity is due to their lower weight, as well as to a continuous improvement of their performance aided in recent years by nanotechnology. However, limited storage stability and reliability are critical for polymer composites designed for structural applications [1-4]. In fact, in service, they are subject to damage due to microcracks that are produced in the structure under the action of various kinds of stresses, for example: a) mechanical vibrations or various types of mechanical stresses, b) sudden temperature changes, c) irradiation by electromagnetic radiation causing direct or indirect rupture of chemical bonds (UV light, γ rays, etc.), d) intentional or inadvertent contact with chemical substances that adversely affect the structure, e) various factors which in combination can contribute to compromising the integrity of the structure. Internal damage is difficult to detect and, once developed, even more difficult to repair. This critical point is a real problem in the field of aeronautic vehicles. In fact, for large components, such as parts of primary structures, several non-destructive damage detection techniques have been developed including ultrasonic, infrared thermography, x-ray tomography, and computerized vibro-thermography. This technology has helped to detect damage but repair of this damage has been limited to reinforced patch bonding and/or bolting. Actually, durability and reliability are still problematic in the field of these structural materials; in fact, in order to achieve the mechanical strength required for many structural applications, highly cross-linked polymeric materials are necessary. The trade off for this gain in mechanical strength is that the resulting materials tend to be brittle and are therefore more prone to developing cracks trough normal usage, ultimately failing.