In the present paper the mechanical behaviour of an epoxy/silica nanocomposite system is analysed, discussing the results from tensile and fracture tests.
Moreover a study on the effect of the curing ...cycle on the mechanical properties of nanocomposites is carried out, considering two different curing conditions. Results indicate that the curing cycle has a significant effect on the overall mechanical behaviour of the nanocomposite. Indeed, while nanomodification always enhances the fracture toughness of the epoxy resin, the strength and the notch strength are shown either to increase or to decrease, depending on the curing process of specimens.
Fracture properties are compared to the theoretical predictions based on a multiscale and multimechanism model recently developed by the authors, showing a satisfactory agreement.
Analytical models are developed for the first time in this work for assessing the in-plane electric, thermal and thermoelectric properties of multi-directional composite laminates based on the lay-up ...and the ply orthotropic properties. In particular, both the apparent laminate Seebeck coefficients along two orthogonal in-plane directions and the complete coupled thermoelectric constitutive law are obtained.
The analytical relationships developed are then validated against the results obtained from a bulk of Finite Element (FE) analyses and against both experimental data taken from the literature and the results from an ad hoc experimental campaign carried out in the present work.
The models developed represent a useful tool for designing composite parts to serve as thermoelectrically-enabled structural elements capable of harvesting thermal energy and converting it into electrical, as for instance from heat dissipation found in several applications.
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The paper reports the results of a project aiming to obtain multifunctional binary and ternary polymer nanocomposites with enhanced mechanical and anti-microbial properties. To this end a DGEBA-based ...epoxy resin is loaded using montmorillonite clays and later used as matrix for glass fibre reinforced laminates. Both binary and ternary nanomodified specimens are manufactured and subjected to mechanical testing. An accurate analysis of the effect of nanomodification on the biological activity is carried out as well.
•Results from nanocomposites with enhanced mechanical and anti-microbial properties are presented.•Epoxy is loaded with nanoclays and used as matrix for glass fibre reinforced laminates.•Binary and ternary nanomodified specimens are manufactured and tested.•The effect of nanomodification on the biological activity is studied.
•Analytical models were developed for the thermoelectric properties of cross-ply composite laminates with transverse cracks.•The models are in good agreement with finite element simulations.•The ...thermoelectric properties depend on the transverse crack density.•For the analysed material systems, a degradation of the power factor is estimated in the presence of cracks.•An increment or degradation in the figure of merit is estimated, depending on the level of thermal anisotropy.
Composite materials, based on carbon fibres and/or nano-modified polymers, are characterised by a thermoelectric coupling. Indeed, an electric potential drop is generated in the presence of a thermal gradient (Seebeck effect), which makes them suitable for thermoelectric applications.
In this work, novel analytical models are presented for the calculation of the apparent in-plane electric, thermal and thermoelectric properties of composite cross-ply laminates in the presence of transverse cracks. The aim of this analysis is to understand the variation in the apparent laminate properties if damage takes place in the form of transverse cracks, this being typically the first damage mode occurring in composite laminates under static and cyclic tensile loadings.
The present work presents a preliminary study on the effect of the filler distribution on the elastic modulus of a nanoparticle filled polymer. To this end, two different theoretical approaches are ...implemented and compared. Both of them account for an interphase layer embedding the nanoparticle, with mechanical properties different from those of the matrix. Conversely, only one of them accounts for the variation of the interparticle distance. The comparison between these models allows to draw some conclusions on the effect of the filler distribution.
In this work, an experimental investigation of the notch effect on clay-modified epoxy resins is carried out, discussing the results from Single Edge Notch Bending tests and Double Edge Notch Tension ...tests on notched components. It is found that when the notch root radius is greater than a limit value, which depends on the clay content, the brittle failure of notched nanomodified specimens is controlled by the material strength. Under this circumstance nanomodification, while enhancing the polymer fracture toughness, might have a detrimental effect on the strength of notched components. This study brings to light a new feature of nanomodification according to which particular care should be used when using nanomodified resins for structural applications in the presence of notches or holes.
The present article investigates the possibility of simulating the electrical conductivity of carbon nanotube-reinforced polymer composites by numerical methods. Periodic representative volume ...elements are generated by randomly distributing perfectly conductive reinforcements in an insulating matrix and are used to assemble an electrical network representative of the nanocomposite, where the nanotube-nanotube contacts are considered equivalent resistors modeled by means of Simmons' equation. A comparison of the results with experimental data from the literature supports the conclusion that a random distribution of reinforcements is not suitable for simulating this class of materials since percolation thresholds and conductivity trends are different, with experimental percolation taking place before the expectations. Including nanotube curvature does not solve the issue, since it hinders percolation even further. In agreement with experimental observations, the investigation suggests that a suitable approach requires the inclusion of aggregation during the volume element generation to reduce the volume fraction required to reach percolation. Some solutions available in the literature to generate properly representative volume elements are thus listed. Concerning strain sensing, the results suggest that representative volume elements generated with random distributions overestimate the strain sensitivity of the actual composites.
The main purpose of this work is to provide a comprehensive overview on the preparation of multifunctional epoxies, with improved antimicrobial activity and enhanced mechanical properties through ...nanomodification. In the first section, we focus on the approaches to achieve antimicrobial activity, as well as on the methods used to evaluate their efficacy against bacteria and fungi. Relevant application examples are also discussed, with particular reference to antifouling and anticorrosion coatings for marine environments, dental applications, antimicrobial fibers and fabrics, and others. Subsequently, we discuss the mechanical behaviors of nanomodified epoxies with improved antimicrobial properties, analyzing the typical damage mechanisms leading to the significant toughening effect of nanomodification. Some examples of mechanical properties of nanomodified polymers are provided. Eventually, the possibility of achieving, at the same time, antimicrobial and mechanical improvement capabilities by nanomodification with nanoclay is discussed, with reference to both nanomodified epoxies and glass/epoxy composite laminates. According to the literature, a nanomodified epoxy can successfully exhibit antibacterial properties, while increasing its fracture toughness, even though its tensile strength may decrease. As for laminates—obtaining antibacterial properties is not followed by improved interlaminar properties.
The main aim of this work is to provide a brief overview of the analytical solutions available to describe the in-plane and out-of-plane stress fields in orthotropic solids with radiused notches. To ...this end, initially, a brief summary on the bases of complex potentials for orthotropic elasticity is presented, with reference to plane stress or strain and antiplane shear problems. Subsequently, the attention is moved to the relevant expressions for the notch stress fields, considering elliptical holes, symmetric hyperbolic notches, parabolic notches (blunt cracks), and radiused V-notches. Eventually, examples of applications are presented, comparing the presented analytical solutions with the results from numerical analyses carried out on relevant cases.
In this work, a peridynamics-based representative volume element approach is implemented to estimate the effective tensile modulus of nanomodified epoxy resins. The results obtained through this ...homogenization procedure are then used as input for the analysis of nanocomposite fracture toughness, which is carried out by exploiting a classical continuum mechanics-peridynamics coupling strategy. In the coupled model, the small-scale heterogeneity of the crack tip region is preserved by implementing the recently proposed intermediately-homogenized peridynamic model. Comparison to experimental data confirms the capability of the peridynamics-based approaches to properly model the effective tensile modulus and fracture toughness of polymer-based nanocomposites.
•Nanocomposite effective tensile modulus is derived through a PD-based RVE homogenization.•RVE homogenization results are used as input for the fracture toughness analysis.•Effect of nanomodification on the fracture toughness is studied through a FEM-PD coupling strategy.•PD-based approaches operate at different length scales.•Numerical results are calibrated by performing tensile tests and mode I fracture tests.
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