A. Martone

Enthalpy relaxation of an epoxy matrix/carbon nanotubes

The enthalpy recovery of an Epoxy/Carbon Nanotube systems (E/CNT) manufactured at low nanotube content, have been investigated by using Differential Scanning Calorimetry. Two different nanotube concentration were considered, 0.5 and 0.1 w/w and results compared with the behaviour of the neat epoxy material. Final results reveal that the aging phenomenon is not monotone with the nanofiller content but a significant “depression” of the physical aging seems be highlighted by the lowest nanotube content, i.e. 0.5 w/w. This observation has not been rationalised yet, although it seems reasonable to correlate this later effect with the topological feature of nanotube network within the hosting epoxy. Future work will verify this hypothesis

Investigation of the Effective Reinforcement Modulus of Carbon Nanotubes in an Epoxy Matrix

Polymer nano-composite matrix could be the ideal solution for a new generation of composite materials. The continuous demand for new high performance polymer composite for various applications, in different industrial sectors, has lead many researchers to investigate the potential use of the carbon nanotubes (CNTs) as nano-reinforcements of polymer matrix for the manufacturing of traditional laminate composite. CNTs have attracted considerable attention due to their unique mechanical, surface, multifunctional properties and strong interactions with the hosting matrix mainly associated to their nano-scale features. CNTs’ impressive mechanical properties, with stiffness and strength values falling within the range of 100-1000 GPa and 2.5-3.5 GPa, respectively, make them ideal candidates to develop novel composites characterized by advanced polymer matrices (Treacy, 1996). Despite the enormous amount of experimental data available in literature (Coleman et al. 2006, Thosterston et al., 2003), there are still controversial results concerning elastic property, strength and fracture toughness; moreover, due to inherent difficulties in processing these unconventional nanostructure as nano-fillers in polymer system, a reliable theoretical correlation of the experimental data is still in shadow. Different approaches to build an appropriate theory for predicting reinforcement efficiency of CNTs within an hosting matrix have been presented in the literature.Indeed, the reinforcement capability of carbon nanotubes in a polymeric matrix will depend on their amount, but, undoubtedly, their arrangement within the hosting medium plays a fundamental role in the load transfer mechanism. For this reason, the state and level of dispersion need to be accounted in any attempt for predicting the mechanical behaviour of the final nano-composite system. In literature the enhancing reinforcement of CNT loading for the Young’s modulus is commonly reported. However, at the same time, discrepancy among the different data is highlighted. Therefore, an important issue for modelling purpose is the lack of a reliable database for this property. Characterization and structure-properties of nano-mechanics modelling research have shown that enhancement in mechanical properties of nano-composites are strongly

Insight on mendable resin made by combining Diels-Alder epoxy adducts with DGEBA

Formation of micro-cracks is a critical problem in polymers and polymer composites during their service in structural applications. In this context, materials endowed with self-healing features would lead to the next polymers generation. In the present paper, an epoxy system integrating Diels-Alder epoxy adducts is investigated by thermal and spectroscopic analysis. The direct and retro D-A reaction have been studied by FTIR and specific absorption bands have been identified. Finally, mechanical tests have been performed on the system. The polymer is able to heal fracture and micro-cracks recovering its stiffness after a thermal treatment.

Multifunctional properties of nanocomposites made by 1D and 2D graphene based fillers

High aspect ratio graphene based fillers with different dimensionalities showed the ability to greatly modify rheological, mechanical, thermal and electrical properties of polymers at very low content. In this work, the effect of filler dimensionality on the multifunctional properties of an epoxy matrix reinforced by both carbon nanotubes (1D) and graphite nanoplatelets (2D) have been investigated across the percolation region.

MULTISCALE MODELING OF HYBRID STRUCTURAL COMPOSITES WITH INTEGRATED DAMPING FEATURES

The aim of this work is to propose a design approach for a multifunctional hybrid composite material that integrates high damping performances while withstanding the required structural features. Hybrid composite consists in a three phases composite where a viscoelastic material is added to the conventional structural long fibers/polymeric matrix laminate. Design addresses the problem of integrating the viscoelastic material within the laminate architecture to exploit its maximum damping efficiency. Key aspect is the definition of a viscoelastic multiscale model starting from the constituents to the lamina, and further to the hybrid laminate properties.An analytical procedure has been developed that uses the strain energy method to evaluate the specific damping capacity for all dimensional scales and classical lamination theory was extended to include the transverse shear effects. The method potentiality has been tested against experimental data from Literature. Possible configurations of hybrid laminates...

Corrosion-resistant self-healing coatings

The use of polymeric coatings with self-healing ability is a viable approach for a new smart corrosion protection strategy. Polymer systems are usually applied on a metal surface to provide an effective barrier against the corrosive species. The protective coatings have to delay the inexorable water uptake, blister or crack formation and delamination. Among self-repairing polymers, in this area of interest, Diels-Alder epoxy resins are particularly appealing for coating application, because the products and intermediates obtained during the healing treatment are stable to aggressive environments, such as the major oxidation agents, air and water. In addition, the chemical stability and crosslinked structure of epoxies are preserved and ensure the coating functionality. An intrinsic mendable epoxy system, containing bifunctional adducts, has been prepared by Diels-Alder reaction. Optical microscopy and nanoindention tests validated the morphological and structural recovery of the coating. Immersion test in saline solution revealed the complete restoration of the corrosion protection for a healed sample.The use of polymeric coatings with self-healing ability is a viable approach for a new smart corrosion protection strategy. Polymer systems are usually applied on a metal surface to provide an effective barrier against the corrosive species. The protective coatings have to delay the inexorable water uptake, blister or crack formation and delamination. Among self-repairing polymers, in this area of interest, Diels-Alder epoxy resins are particularly appealing for coating application, because the products and intermediates obtained during the healing treatment are stable to aggressive environments, such as the major oxidation agents, air and water. In addition, the chemical stability and crosslinked structure of epoxies are preserved and ensure the coating functionality. An intrinsic mendable epoxy system, containing bifunctional adducts, has been prepared by Diels-Alder reaction. Optical microscopy and nanoindention tests validated the morphological and structural recovery of the coating. Immersion test in...

An integrated strategy to promote self-healing at interface in composites based on Diels-Alder epoxy

The self-healing polymers are a class of smart materials able to recover after sustaining damage. An epoxy resins containing Diels-Alder (D-A) adducts in the backbone and related single-fiber compo...

Mechanical Properties of Nanolaminates Based on Graphene Nanoplatelets

Abstract Graphene-based nanocomposites assume different architectures depending on manufacturing process, e.g., paper-like structures received great success for supercapacitor application due to their outstanding electrical and thermal conductivity. Recently, a nacre-like architecture, named nanolaminate, attracted the attention of scientists since it should be considered as bulk material. There are several micromechanics models for the prediction of the elastic properties of nanocomposite materials, based on the geometry, orientation of the filler, elastic properties of the filler and matrix. The stiff constituent phases (graphene platelet) in the structural materials bonded together by the soft constituent phases result in the so-called brick-and-mortar (B-and-M) structure. The effect of filler properties will be discussed by considering the analytical and numerical procedures available in literature for bidimensional filler composites. Several critical physical mechanisms may affect the reinforcing effects, including the agglomeration, stacking up, and rolling up of graphene sheets.

Phenomenology of Shape Memory Alloys

Abstract The strong demand for high performance structural and mechanical systems for aerospace, defense, and advanced manufacturing industries has promoted the evolution of advanced materials. Materials cannot respond to changes of the surrounding environment and are not able to operate under the service conditions for which they are not optimally designed. There is a significant need for the evolution of advanced active materials with enhanced performance whose elastodynamic response can be optimally adapted in real time under a broad range of service conditions. Unlike the common structures, shape-memory materials are stimuli-responsive materials, they have the extraordinary feature to respond to external stimuli adapting their structure to the surrounding environment and compensating for undesired effects. A shape change because of a temperature change is called thermally induced shape-memory effect.