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This paper presents an analysis of a composite cell at a micro level. The authors modeled the interface between a micro sphere and a polymeric matrix for two cases: an interface characterized by a strong bond between the two involved bodies and an interface with low friction between the micro sphere and the polymeric matrix. Even if these models are ideal images of actual composites, the analysis of strain and stress distributions reveals there is a big difference in the mechanical behaviour of the two micro cells. These two cases were analyzed considering a perfect elastic behaviour of involved materials. The shape and the intensity of stress distributions are different for the analyzed models. A weak interface makes the matrix to have restrained zones with high values of von Mises stresses, concentrated on top and bottom of the sphere (on the loading direction). An actual cell of a similar composite (polymeric matrix and a micro sphere as reinforcement) could not have an „extremist” behaviour as these two here presented, but an intermediate one, depending on actual properties of the materials and the nature of the interface. Keywords: micro cell composite, strain distribution, stress distribution

In this paper we studied the dyeing behaviour of polyester fibers from recycled polyester and virgin dyed with Foron brilliant rot SGL (CI Disperse Red 121). The amount of dye fixed recycled fiber is higher than that of virgin. Elemental analysis confirms a slight change in the carbon and oxygen content of recycled fiber compared to virgin. Thus the recycled polyester fiber carbon content is higher than virgin fiber in oxygen exchange is less. Dyed samples were treated with AgNO3 in order to confer antibacterial properties. The analyses SEM/EDAX have highlighted the presence of silver ions on the surface of fibers. Keywords: dyeing, recycled PET, virgin PET, disperse dye, antimicrobian effect

In this paper the buckling problem is solved for the laminated composite structures from a thin-walled metallic cylindrical shell which is strengthened by fiber-reinforced polymers. The research concerning the influence of composite thickness and fiber orientation on axial critical buckling load is executed. For linear buckling problem, the purposed method is based on modified relations for an orthotropic cylinder. The method was verified by comparison with buckling theories of laminated composite shells and with numerical results based on finite element method. Keywords: lamina/ply, buckling, analytical modelling, numerical analysis

This paper analyses the influence of processing temperatures of polyamide 6.6 Grivory type HTV-3H1 noir 9205, polyamide 6.6 Grivory type HTV-45H1 noir 9205 and polyamide 6.6 Grivory type HTV-6H1 noir 9205 on some mechanical properties, when injecting items used in various technical articles. The test-specimens on PA 6.6 Grivory type HTV-3H1 noir 9205 were molded at the following injection temperatures: 310, 320, 330, 340 and 350°C. The test-specimens on PA 6.6 Grivory type HTV-45H1 noir 9205 were molded at the following injection temperatures: 320, 330, 340, 350 and 360°C. The test-specimens on PA 6.6 Grivory type HTV-6H1 noir 9205 were molded at the following injection temperatures: 330, 340, 350, 360 and 370°C. These specimens were tested using methods for determination of the following mechanical properties: tensile strength, Izod impact strength and hardness (Shore). For all these polymers, it was determined that increasing of injection temperature results in insignificant changes of hardness. The Izod impact strength decreases with increasing the injection temperature. After reaching the minimum value, Izod impact strength increases again if the processing temperature is raised further. The tensile strength at break increases with increasing the processing temperature. After reaching the maximum value, tensile strength at break decreases if the processing temperature is raised further. Keywords: polyamide 6.6 (PA 6.6), tensile tests, Izod impact test, Shore Durometer hardness test

The present study evaluates the marginal adaptation of fixed partial prosthesis made from resin composite. The main goal is to obtain restorations with excellent aesthetics and extremely high quality which increase the lifetime of the prosthesis system - dental structures. The method allowed the observation of defects that might occur during the technological processing, as well as their correction. It was used the 3D Shape software with which have been achieved scans for the virtual presentation the marginal adaptation. Following the investigation it was showed, that the cementation is extremely important, the errors occurring in this phase are influencing of the final results and behaviour. Composite resin fixed partial prosthesis are restorations which through a correct technology can compete with the ceramic fixed partial dentures. Keywords: aesthetic restoration, marginal adaptation, defects, 3D Shape software

In the last years, researches regarding the manufacture of polyamide parts using selective laser sintering process have developed increasingly more because of the advantages this materials offer. This paper was focused on a comparative study about the mechanical proprieties and surface roughness of parts manufactured by Selective Laser Sintering (SLS) from PA2200 powder. Tested parts were achieved on DTM Sinterstation 2000 Machine and EOS Formiga P 100 Machine. The results obtained lead to the conclusion that the mechanical proprieties obtained for the test parts made at 7,5W laser power on DTM Sinterstation 2000 Machine, are close to the results obtained for the test parts made at 30W on EOS Formiga P 100 Machine. Keywords: Polyamide, Selective Laser Sintered, mechanical proprieties, roughness

The concern for quality assurance and improvement of the manufacturing processes of plastic materials is of great interest to industry companies offering the guarantee to ensure the conformity, performance, competitiveness and profitability. This paper addresses the importance of improving the quality of plastics manufacturing processes, on high (flow) performance. It illustrates the application of the “Six Sigma” statistical method for injected products that have certain defects / nonconformities, especially dimensional manufacturing. Keywords: plastic products, quality, six sigma, manufacturing process, efficiency

The bile duct system has two distinct components: one intrahepatic and another extrahepatic. Both components are subject to large anatomical variability. Knowledge of intraparenchimatous bile duct system distribution is particularly useful for planning and performing major surgical resection and liver transplantation. For this reason, the training of students and medical residents must use liver corrosion casts. On the 130 pieces of hepatic corrosion casts, a percentage of 80.75% of cases have modal typology, homologated by Terminologia Anatomica (1998). On a percentage of 19.25% of the studied cases were found major variations of the intrahepatic bile duct system (classified into four morphological types). In 16.15% of cases, the posterior branch in his passage to the left hepatic duct intersects the main portal fissure. Medial and lateral branches showed no major variations on the studied material. Use of human intrahepatic bile duct system corrosion casts with major anatomical variations, can compensate for lack of clinical material in training of medical students and residents. Keywords: corrosion casts, intrahepatic bile duct system, major variations, training

Chitosan (CHI) and poly(acrylic acid) (PAA) polyelectrolyte multilayers were constructed onto silica microparticles with particle diameter of 40 – 60 mm (Daisogel type). The multilayers were subject to two post-treatment strategies: (i) immersion in an aqueous solution with pH = 2.4 for 5 min, followed by immersion for 1 min in water and thermal treatment at 120oC for 60 min and (ii) cross-linking with glutaraldehyde for 60 min. The sorption properties for a cationic dye were investigated taking methylene blue (MB) as a model. The reusability of (CHI/PAA)n multilayers deposited onto Daisogel microparticles in the consecutive sorption/desorption cycles of MB was investigated as a function of the number of double layers and the post-treatment strategy. Keywords: polyelectrolyte multilayer; chitosan; poly(acrylic acid); methylene blue; silica

The aim of the study was to compare using atomic force microscopy the surface roughness of three types of composite resins after finishing and polishing procedure with three different systems. A hybrid (Valux Plus, 3M ESPE), a microhybrid (Filtek Z 250, 3M ESPE) and a nonohybrid (Herculite XRV Ultra, Kerr) composite resins were chosen for this study. A number of 28 samples having 10 mm in long ,7 mm in width and 2 mm in high of each composite resin were obtained. The samples were equally split in 4 groups. In control group 7 specimens of each material received no finishing and polishing treatment after being cured under plastic matrix strip. In the first study group 7 samples of each material were finished using fine, safe end taper tungsten carbide bur, 7 samples were finished using superfine needle diamond bur and 7 samples used diamond impregnated one stage polisher. The surface of all composite samples was analyzed using atomic force microscopy. The results were expressed as root mean square surface roughness (nm). The results were statistically analysed using ANOVA and post hoc Bonferroni test at a 0.5 significance level. Significantly differences were obtained in the surface roughness of all three tested composite resins after finishing and polishing when comparing to surface roughness from control group. The one-step diamond abrasive polisher leaded to a significant lower surface roughness for all three composite resins when comparing to the surface roughness when tungsten carbide bur or diamond bur were used. Surface roughness of Valux Plus was higher than that observed for Filtek Z 250 or Herculite XRV Ultra, irrespective of the system used for finishing and polishing. The surface roughness of composite resins is in relation with the type of composite resin and the type of finishing and polishing system. The one-step diamond abrasive polisher was more efficient in obtaining smooth surface when comparing to tungsten carbide bur or diamond bur. The nanohybrid composite resin has a lower surface roughness when comparing to microhybrid and the hybrid composite resin after finishing and polishing. Keywords: composite resins, surface roughness, AFM, finishing and polishing system