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We deduced the equation of motion for free vibrations using Mohr-Maxwell method, considering that the bar is requested to bending by the inertial forces and by the damping forces. We experimentally obtained the dynamic response for sandwich bars with polypropylene honeycomb core, which have the exterior layers made of epoxy resin reinforced with steel fabric. In addition, we determined the damping coefficients per unit mass and per unit length of the bar, for bar with core thicknesses equal to 10, 15 , 20 mm; width of 40 and 60 mm, and the free length of embedded bar equal to 200, 250, 300 and 350 mm. For each type of bar studied, we determined the relationships of exponential type for the calculus damping coefficients (mentioned above), according to the free length of the embedded bar. Keywords: sandwich beam, damping factor, polypropylene honeycomb, free vibrations

The purpose of this paper is to show the possibility of finding the location and to describe internal discontinuities in plates made of plastic materials using non-destructive evaluation methods. Their effect on the mechanical behaviour is also evaluated by means of numerical calculus. The technique of computer tomography („CT”) is used as a non-destructive evaluation method whereas the numerical calculus is realized by the finite element method. Keywords: computer tomography, discontinuity, finite element analysis

The paper refers to the new approach in bone grafting: biomaterials. Many artificial bone substitute materials are currently available for use in orthopaedic trauma surgery. The selection of these materials is more and more difficult as many bone substitute products are now available for use and this method led to a new approach, although the autologus bone grafting still represents the “gold standard” in bone reconstruction surgery. Keywords: bone grafting, biomaterials, reconstruction, fracture

The objective of this paper consists in the minimization of warpage problems which depend on the process parameters during injection molding of thin wall plastic parts using an optimization technique involving Taguchi method, S/N ratio and ANOVA method. For this purpose, a number of experiments are carried out by utilizing the combination of process parameters based on a three-level L9 Taguchi orthogonal array table. To achieve the minimum warpage, the optimum level of process parameters is determined. A drain with 8 sockets is investigated, where melt temperature, mold temperature, injection speed, and packing pressure are selected to be the process variables. The results show that the optimum parameters that can minimize the warpage problem are: melt temperature (190°C), mold temperature (30°C), injection speed (70 mm/s), and packing pressure (55 MPa). The most effective factor on the warpage is packing pressure with a general influence of 55.71%. Keywords: plastic injection molding; thin wall parts; warpage; Taguchi method; S/N ratio; ANOVA method; optimization

The present paper aims to present a method for redesigning plastic products using the Reverse Engineering technique. The originality of this paper stems from its integration of modern scanning techniques and reverse engineering with traditional manufacturing techniques. The paper presents a case study about the redesign of an existing product for which no technical documentation is available, using three distinct phases: reverse engineering, modeling analysis and redesign, manufacturing and testing.. Keywords: redesign, reverse engineering, mould, polymeric material

This study presents new findings of the water/ethanol (ratio) influence on the aniline hydrochloride polymerization process in presence of ammonium persulfate. Water/ethanol mixtures in presence of monomer hydrochloride, as proved by the conductometric, spectrophotometric and refractometric investigations, are far from ideal solutions and promote a partitioned environment , for the polymerization process. By controlling this key parameter (water/ethanol ratio) the polymerization can be shifted from a initial dispersion process to a solution one, followed by precipitation. The associated phenomena revealed modification in terms of conversion, structure (FTIR, UV-VIS), morphology (SEM), thermal stability and doping agent retention (TGA-DTG). Keywords: conductive polymers, aniline hydrochloride, water/ethanol system, polyaniline

The options to deposit chemically a functional composite copper-diamond coating from trilonic electrolyte have been studied with respect to textile polyethylene terephthalate substrate. The optimal basic composition of the electrolyte for surface treatment and the optimal conditions of deposition has been found from the viewpoint of the deposition rate, respectively the thickness of qualitative layer of the copper matrix. A systematic study of the influence of different types and concentrations of surface active agents (SAA) and different temperatures of the electrolyte at continuous air flow stiring has been realized, aimed co-deposition of copper metal-matrix composite, containing diamond particles (sizes, varying within the range 3-70mm). Keywords: coating; fabrics/textiles; surface treatments; metal-matrix composites (MMCs); functional composites

In this article, some advantages and disadvantages of the incorporation method of azobenzene moieties in several polymer matrices (polymethacrylate, poly(styrene-alt-maleimide), poly(oxazoline-co-methacrylate), poly(methacrylate-co-methacryloxypropyl trimethoxy-silane)) are highlighted. Their physical properties (molecular weights, glass transition temperatures, chromophore load, solubility, and solvatochromism) are discussed with regard to their macromolecular architecture. Solvent effect on the UV-Vis absorption spectra of azo-polymers was investigated using Reichardt’s solvent polarity scale and Kamlet-Taft multiparameter equation. Kamlet-Taft equation revealed that hydrogen bond acceptor properties and dipolarity/polarizability of the solvent have a significant contribution upon the solvatochromic behaviour of azopolymers. Keywords: azobenzene, side-chain polymers, solvatochromism, Kamlet-Taft equation

A series of six new experimental light-curing dental composites based on two Bis-GMA-type oligomers, quartz and nano-fluorohydroxyapatite (nano-FHAP), in different ratios, were prepared. The paper refers to the characterization of organic and inorganic phases from the uncured composite pastes and determination of the properties of the light-cured composite materials. Differential scanning calorimetry was used to measure the heat of polymerization of the monomer mixtures. Investigation of nano-FHAP was made by transmission electron microscopy TEMBF, HRTEM and X-ray diffraction. The mechanical strengths, water sorption and solubility were determined. We came to the conclusion that for the same monomer mixture, the water sorption and solubility values increased with the content of nano-FHAP in the composite material, but there remained in the limits of ISO 4049/2000 for the compositions comprising up to 50% nano-FHAP in the filler. The highest mechanical strengths were obtained in the case of composites containing 75% quartz in the filler. Keywords: dental nanocomposites, extent of polymerization, mechanical properties, water sorption, solubility

Fibre Reinforced Polymers (FRP) confinements on square and rectangular sections behave differently from confined circular sections. Confining inward pressure over the entire circular section is uniform, whereas in non-circular sections confining pressure development is inconsistent. As a result, these sections could be divided into the distinct properly and partially confined areas. Presence of these partially confined regions would much reduce influence of FRP confinements to increase concrete’s peak strength and ultimate strain. To evaluate confinement effectiveness, effect of mentioned areas must be taken into account precisely. This paper describes a theoretical model adapted to seismic strengthening and retrofit of the square section RC columns confined with advanced composite materials. The model is the author’s earlier proposed one calibrated with cautious survey on the existing test data. This model takes into account geometrical parameters of the column shape such as overlapping length and corner rounding radius; furthermore both concrete and FRP confinement mechanical properties. Finally it proposes a new shape factor for the square sections which plays a major role in effectiveness evaluation of FRP confinement. Keywords: Fibre Reinforced Polymers, square section, Reinforced Concrete columns, strengthening