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This article presents research on the influence of a coupling agent -methacryloxypropyltrimethoxysilane (MEMO) and cross-linking agent dicumyl peroxide (DCP) on thermal and nanomechanical properties of neat and waste polyethylene (WPE) as well as their blend. Modification of nanosilica by silanization was performed under supercritical conditions of carbon dioxide-ethanol mixture. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), indentation as well as scratch testing at nanoscale were employed for characterization of the polymer matrix with unmodified and modified nano-SiO2 particles. Low amounts of the peroxide and silanized nano-SiO2 particles in the composite formulation significantly improved thermal and tribo-mechanical behavior at nanoscale. POLYM. COMPOS., 34:1710-1719, 2013.

This study reports research related to different preparation methods and characterization of polymer nanocomposites for optical applications. The Eu-ion doped Gd2O3 nanophosphor powder with different nanoparticle content was embedded in the matrix of PMMA. Preparation was carried out by mixing molding (bulk), electrospinning (nanofibers) and solution casting (thin films) with neat particles and particles coated with AMEO silane. Among the pros and cons for proposed methods, the mixing molding enables to avoid solvent use while the best deagglomeration and nanoparticle distribution is gained using the electrospinning method. The results of dynamic mechanical analysis (DMA) and nanoindentation revealed that the storage modulus of the composites was higher than that of pure PMMA and increased with nanophosphor content. Surface modification of particles improved the mechanical properties of nanocomposites.

One of the more important developments in magnetic materials, polymer bonded magnets, have opened a new world of application opportunities. The Nd-Fe-B/polymer composite materials offer an excellent combination of strong magnetic and dynamical-mechanical properties. However, the transition temperatures of filler and matrix should be selected carefully considering the future application. Uniform particle distribution and good adhesion between Nd-Fe-B powder particles and polymer are essential for the quality of the composite, while stiffness of polymer matrix is one of the influencing factors as well. The damping properties of Nd-Fe-B/polymer composites with 15 wt.%, 50 wt.% and 75 wt.% of Nd-Fe-B powder were studied by dynamic mechanical analysis and compared with a pure polymer sample. Thermal stability was analyzed using a simultaneous differential scanning calorimetric and thermogravimetric analysis technique.

Composites with nano-SiO2 particles and high density polyethylene (HDPE) matrix were produced by hot pressing with various particle contents and particle surface treatment using commercially available silane coupling agents: gamma-methacryloxypropyltrimethoxy silane and gamma-glycidyloxypropyltrimethoxy silane. The influence of the particle treatment on the mechanical properties of composites was determined by compression and indentation tests. Additionally, numerical analysis was performed in order to calculate Young's modulus and stress concentrations for various particle contents in order to provide reference data by simulating micro- and macro particle composites with perfect bonding to the matrix.

Considering the conditions to which steels used for the manufacture of steam pipelines are exposed, the micromechanism of their destruction in exploitation is exclusively the ductile one. In order to make an estimation of the level of the damage that occurs in exploitation, in this paper a combined experimental and numerical procedure has been developed based on micromechanical or local approach to the fracture mechanics of metallic materials. After the analysis of the results obtained for micromechanical criterion of failure for virgin steel and that used in the steam pipeline, a proposal for prolongation of the working life of tested steel for steam pipelines until the next overhaul is given.

In recent years, optical fibers have received attention as sensors for the purpose of in-service health monitoring in composite materials. Advantages of optical fiber sensors over conventional sensing methods are well-known and include resistance to corrosion and fatigue, similarity of their material properties to the reinforcing fibers, small, flexible and lightweight nature, immunity to electromagnetic interference and high response bandwidth. These features enable their embedding into composite structures and access locations where other sensing methods cannot easily probe. This paper evaluates the feasibility of real-time monitoring of indentation damage in composite laminates from indentation loading using the embedded intensity-based optical fiber sensors. An optical fiber sensing system, which relies solely on monitoring light intensity for providing indication of the composite structural health, offers simplicity in design and cost-effectiveness. For this, aramid/polyvinylbutyral (PVB) laminates with embedded optical fibers were fabricated. Three configurations of woven composites were tested, namely aramid/PVB, metal/PVB and aramid/metal/PVB. Several stacking sequences of aramid and metallic woven layers were used for investigations. Initiation of damage and fracture during testing was detected by observation of the intensity) drop of light signal transmitted through optical fiber.

An application of the embedded intensity based fiber optic sensors (FOS) for fatigue damage detection in cantilevered composite rods is presented. During the fatigue test with constant amplitude of oscillations, the deflection and the intensity of optical signals were acquired constantly until the optical signal drop has been observed. Characteristics of optical signals are described and discussed. In order to quantity the state of damage just after a significant change in optical signal intensity. the numerical verification of the reduced stiffness, based on static measurements, is carried out.

The influence of particle geometry and volume fraction on the mechanical properties of a hydroxyapatite (HAp) particulate reinforced polymer (poly-L-lactide and collagen) matrix composite was investigated through finite-element (FE) analysis. For cube-shaped (near sharp and curved corners and edges) embedded particles, it was found that the maximum stress concentration factor (SCF) in the matrix decreases with an increase of the HAp particle volume fraction (PVF). The maximum stress concentration in the matrix material containing a spherical inclusion has low sensitivity to the PVF. The compressive Young's modulus was found to be slightly dependent on particle shape, but very sensitive to PVF. Calculated stiffness values from FE analysis were compared to the experimental results available in the literature and with predictions from the Halpin-Tsai model.

The influence of inclusion geometry and volume fraction on stiffness behavior of a particle hydroxyapatite filled polymer (poly-L-lactide and collagen) matrix composite was investigated by finite element. analysis. The compressive Young modulus was found to be slightly dependent on the particle shape, but very sensitive to the volume fraction of the filler particles. It was also shown that filler aspect, ratio, in the range of 1.0-2.5, had an impact on the maximal stress values, while the stiffness values were only barely influenced by the aspect ratio.

A three-dimensional (3D) finite element (FE) analysis of the stress concentration factor (SCF) in biocomposite model cell has been performed. The model composite consisted of a hydroxyapatite hard particle (HAp) embedded in poly-L-lactide soft matrix (PLLA). Two cases were considered, namely the shape of the particle was held constant while the volume fraction of HAp was varied and the particle shape was changed whilst the volume fraction was constant. For block shaped embedded particles, it was found that the SCF decreases with an increase of the HAp particle volume fraction. It was also found that the shape of reinforcing particles had little effect on the mechanical behaviour of material.

A typical intensity-modulated optical fiber sensor system consists of a light source, a sensing device, within which the intensity of light is altered by the measurand in some way, a detector to measure the intensity of the transmitted signal and optical fibers to carry light between these components. The optical fiber coating interaction with the host material plays a major role in determining the proper transfer of load from the structure to the optical fiber. Three-dimensional (3D) finite element (FE) model of the structure was performed to study and predict the behaviour of the stress/strain fields in and around acrylate coated embedded optical fibers in flexural test coupons of carbon fiber composite. The modeling results and the fracture surface scanning electron micrographs suggest that the soft acrylate coating is debonding.