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Impact damage in structures made of composite materials is a major concern since such damage can be introduced during the life of the structure, and its mechanical properties can be dramatically reduced as a result. Many efforts have been made in order to predict the damage and residual properties after impact. In the present paper a previously verified model is used in order to evaluate the residual tensile strength of woven fabric laminated composites. The model takes into account the number of plies; the impact energy and the stacking sequence. The effect of the thickness on the residual tensile strength as well as on the impact energy threshold was also examined. The predicted values seem to be a very good approximation of the experimental results. Keywords: Laminate, reinforcement, impact device, residual stiffness, uniaxial tension

Polyphenols have antioxidant character due the presence of several phenol functional groups. In human health, they are thought to be useful in combating oxidative stress, a syndrome causative of neurodegenerative and cardiovascular diseases. The main source of polyphenol antioxidants is nutritional, since they are found in most vegetables and fruits. We used tannic acid as polyphenol model. The polyphenols are encapsulated in chitosan matrices because chitosan is a natural bioactive material and it is pursued to release the polyphenols only in a certain medium. In this paper, the obtaining strategy of chitosan nanostructurate membranes with tannic acid, as Controlled Delivery System, is presented. Keywords: chitosan, cationic surfactant, tannic acid, morphological analysis

The thermal decomposition behaviour of some phosphorus-containing polyesters and a polyesterimide was studied using thermogravimetric analysis in air at several heating rates between 5°C/min and 20°C/min. The results of this study, realized for polyesters with phosphorus linkage as pendant group, were compared with the behavior of some polyesters having the same backbone structure, with phosphorous in the main chain, respectively without phosphorous. A kinetic model of the reaction order was also proposed for thermal degradation of studied polymers by using Vyazovkin method. Keywords: phosphorus-containing polymers, thermal degradation, flame retardant properties

Aromatic hydrocarbons especially 1,2 benzanthracene and perylene were effective in suppression of carbonyl and hydroperoxide formation upon irradiation, while carbon structures (carbon black and graphite) seems to produce increased radiation degradability, as it was shown by IR data. Pyrene and perylene induced increased stability to thermal oxidation subsequent to irradiation. The radiation induced formation of some hydroxyl groups grafted on degraded polynuclear structure has been supposed to explain the observed increased stability. Several changes in IR absorption bands observed with these irradiated hydrocarbons support this hypothesis. Keywords: chemiluminescence, aromatic compounds, degradation, polyethylene

In the generation of new materials replaceing the metals, taking into account their characteristics and future perspectives, one should pay a special attention to the composite materials, which were named consolidated plastic materials, just a short time ago. This paper emphasizes that the quality of the drilling tools and the geometry of their active part, the dimensional precision and of geometric form and also the quality of the surfaces processed by drilling, depend especially on the nature of the composite material and of the reinforcing fibers. Keywords: composite material, drilling, machining, wear

In this study the polymer transport dynamics in a 2D lattice model is investigated. The dependence of the polymer escape time through a nanometer pore on the stiffness and the monomers number of the polymer is demonstrated. We have also proved the major effect of superimposed electric field on the polymer translocation. Keywords: 2D lattice model, Langevin equation, nanopore, transport phenomena, translocation time

The paper deals with the synthesis and characterization as polymer processing aids, i.e. as plasticizers and/or lubricants, of some mixed (unsymmetrical) diesters of adipic acid by using aliphatic alcohols of variable length, such as C4, C6, C2-6, izo C10 and izo C13, along with complex aliphatic-aromatic alcohols, like 2-phenoxyethanol, 2-[(o-sec-butyl)phenoxy]ethanol and 2-[(p-nonyl)phenoxy]ethanol, respectively. The diesters derivatives obtained this way showed plasticizing and/or lubricating properties. The variation of such properties was studied by varying the polar / unpolar ratio within each structure of the considered product. Interesting correlations were recorded and the theoretical premises were fully proved. Keywords: unsymmetrical adipic diesters, plasticizers, lubricants, phenoxy-ethanols

Lubrication aspects, in extreme operating conditions, highlights important problems concerning bearings design or greases behaviour management for given operating conditions. The researches that were done in the last period were focused on greases service life and behaviour versus rolling bearings operating conditions but, it must be emphasized, that some particular aspects such as the presence of the electrical fields were less studied. Some results in this specific area were previously forwarded by Prashad who highlighted issues such as greases resistivity modifications with time, particular bearings and lubricating greases damaging mechanisms. Aspects concerning temperature influence on grease resistivity, correlations between greases structural, physical and chemical deterioration and bearings specific failures, in the presence of the electrical field, are questions that must be answered. These problems are very important because electrical rotating machines support bearings reliability is strongly dependant on greases service life and performances. The paper presents some correlations between the electrical field characteristics and electrical motors rotors support rolling bearings greases deterioration based on lubricant’s SEM and raceways microscopical analyses. Starting from these results it can be concluded that rolling bearings deterioration under the influence of the electrical field is a complex phenomenon with effects, both, on lubricating greases and bearings rolling contact surfaces. From this point, a greases deterioration model, in the presence of the electrical field, will be proposed. Keywords: lubricating greases, electrical field, deterioration

This paper presents studies regarding the behaviour at heat treating of an AlCu4Mg1 aluminum alloy. The experiments were made on laboratory conditions and can be applied in industry. The proposed methodology can be resumed in: adopting the heat treating technology for the proposed alloy; choosing the necessary working installations in order to realize the heat treating for the specified alloy; choosing the tools and the machines used for studying the chemical and mechanical characteristics; programming the experiment and analytical interpretation of the results. For experiments, was used a study charge (9 treated parts) and a test part (a non treated part). Every part from the study charge had a particularly final heat treating technology. Test part is not treated and the mechanical characteristics are determined in this situation. As a conclusion, the paper presents the algorithm for applying the optimum heat treating in order to obtain the necessary properties for the working parts. Keywords: aluminum, plasticity behaviour, heat treating, chemical composition, elasticity

Due to their important and special characteristics composites have known a continuous development lately. Consequently there has been given great attention to improve, both, their manufacturing and machining technologies. In machining, milling represents an important procedure and, as there are not many data concerning process parameters dependence, some statistic models were considered worth to be determined. So, there has been studied Romanian glass fiber reinforced polymeric composites and have been obtained two mathematical relations of surface roughness dependence - Ra parameter- on some milling process variables. Keywords: composites, glass fibers, milling, surface roughness