Volume 57, Issue 2

Abstract: Thermoplastic polymers have found widespread applicability in electronic industry owing to their facile processing and relatively low costs. Transparent polymer foils, like polyethylene terephthalate (PET), can be utilized in manufacturing components for liquid crystal display (LCD) devices. This work is focused on surface processing of PET through different procedures. The induced surface modifications of polymer samples were analyzed by optical microscopy. Contact angles of nematic drops on PET film are measured to evaluate how the method of surface modification reveals that the surface texturing affects the interactions of polymer with the liquid crystal. The influence of created surface anisotropy on the work of adhesion at polymer/liquid crystal interface is analyzed. Preliminary assessment of nematic orientation on the surface of modified PET foils is performed using polarized light. The results were discussed in regard with the used methodology to adapt the surface of the PET films to achieve optimal orientation of nematic molecules. The obtained data will open new perspectives on processing polymer foils as alignment layers used in LCD devices.

Abstract: Abstract.The paper aims to present research on the determination of the coefficient of acoustic absorption as a function of frequency, for composite monolayer plates (made of: MDF - wooden dried agglomerated fibres with medium density, RWB – rebated wood from dried beech, PS - extruded polystyrene) and multilayer (with outer coatings of: MDF, RWB and polymeric core of extruded polystyrene). The sound-absorbing behavior of such plates is highlighted in the cabins made of multilayer structures.

Abstract: In this study, a new solution for the development of an antiradar camouflage by overlaying several mono-pigment polymeric structures in a composite structure is provided. In this respect, powder materials with antiradar properties (carbon nanotubes, graphite, active charcoal, aluminum trioxide) were embedded in polymeric matrices. The performances of the developed products were tested using an experimental device for the measurement of electromagnetic efficiency within the frequency range from 1 to 18 GHz.

Abstract: Lately, PP-R pipes have become increasingly popular in terms of drinking water installations and heating. Comparated to the classic pipes from copper or steel, pipes from propylene are much easier to use, they have obvious qualities and they are marketed at a much lower price. The study aims a comparative analysis of the physical-mechanical properties of the four most common types of pipes from propylene, which are currently found in commerce : simple without insertion(PP-R), with insert of composite fiber (PP-R-CF), with insert of basalt fiber (PP-R-BF) and with insert of aluminium (PP-R-AIF). Experimental research showed that from the point of view of thermal expansion, the best behavior is from the pipes from propylene without any insert and the value of the thermal expansion coefficient for the reinforcement pipe with basaltic fiber is very small. After these attempts at tensile, it resulted that all four samples which were analyzed from the point of view of the tensile strength, don’t exceed the limit that was given by the manufacturer (10-30 MPa), the values obtained being: for pipe from polypropylene of 17 MPa, for pipe from polypropylene with insert of aluminium of 18 MPa, for the test tube from pipe of polypropylene with insert of basalt fiber of 29 MPa and for the test tube from pipe of polypropylene with insert of composite fiber of 30 MPa. Therefore, from the point of view of the behavior at tensile and bending, the best behavior is from the pipes from polypropylene with insert of basalt fiber and pipes from polypropylene with insert of composite fiber.

Abstract: Background. The macroporous polyurethane ether foam was introduced in the medical field, as early as the 90 ties, for the Vacuum-assisted closure (V.A.C.) of a wound. We describe our experience after treating abdominal wound dehiscence in a group of elderly gynecological patients with NPWT (Negative Pressure Wound Therapy), using ether foam coated with a silver layer. We reviewed elderly patients chart data that underwent abdominal surgery complicated with wound dehiscence treated with VAC for eighteen months. In all patients, the system used was the standard GranuFoam Silver™ dressing (different extents), which was usually replaced every 48/72 h. A total of 15 consecutive female patients were included. The median age was 67.3 (58-71) years. Duration of VAC treatment was median 14.2 (11-34) days, and we saw an improvement in wound repair but also clearance of S.S.I. on the third day after applying V.A.C. Ulta™. Definitive secondary closure of the wound was obtained in all patients, as the infection’s site clearance. The abdominal VAC treatment with GranuFoam Silver™ dressing in patients with infected abdominal wound dehiscence is safe and has proper patient compliance. The latest evolution of the silver foam polyether dressing, in conjunction with NPWT therapy, offers a better antimicrobial effect and shorter healing stage.

Abstract: Diabetes mellitus (DM) and cardiovascular diseases (CVD) represent worldwide, major health problems. Frequently, diabetic patients may require therapy with implantable intra-cardiac electronic devices. In this article, we analysed the complications related to the presence of polymer-coated electrodes leads occurred among 351 patients, carriers of implantable electronic intra-cardiac devices: permanent pacemakers (PPM), cardiac resynchronisation therapy (CRT) or implantable cardioverter-defibrillators (ICD). Of all these patients, 99 (28.20%) had type 2 DM (p=0.022), double than the prevalence of DM in the general population (11%). Only two patients with PPM and DM had fractures of electrodes leads and one was diagnosed with right heart infective endocarditis, but no non-diabetic patient developed any complications related to the presence of polymer coated electrodes leads.

Abstract: The paper presents the manufacturing process of advanced composite wind turbine blades designed for an experimental counter rotating vertical wind turbine (CR-VAWT). An iterative approach was used to present the manufacturing process of turbine blades starting from presentation of the turbine structure and material description as well as all manufacturing process stages. Two types of turbine blades were successfully manufactured using metallic molds and a cost-effective manufacturing technology. Based on the turbine blades obtained it can be said that the selected manufacturing process showed good results, very similar with results expected in case of using advanced technologies (i.e. autoclave technology.

Abstract: The aim of this in vitro study was to evaluate the characteristics of four commercial dental composites: two dual-curing luting resin cements and two indirect composites for crowns and bridges. The novelty of the study consists in the use of combined characterization methods for the investigated materials, namely: after maintaining the samples in the water/ artificial saliva, besides sorption, the surface degradation of the samples was observed after their immersion period; thereafter, the immersion medium was lyophilized and then the percentage of residual monomer found in the medium was determined by HPLC. After 44 days, small concentrations of monomers have been determined in the aqueous/saliva extracts. SEM images show that the samples from each class of material, with a higher content of inorganic filler, exhibit a larger erosion of the surfaces after contact with water compared to the other two samples that show a larger erosion of surfaces after contact with saliva than with water. The surface of the dual-curing resin cement with a higher content of inorganic filler is the smoothest from the samples exposed to saliva, instead the other resin cement is the roughest, as shown by AFM analysis. The overall observation reveals that the samples kept in saliva are rougher than the ones kept in water. Smooth surface materials of both classes of materials ( with a higher content of inorganic filler) have absorbed a higher amount of water / saliva compared to materials with a rougher surface.Water sorption in the composite resins is influenced by the hydrophilicity of the monomers, the nature and size of the inorganic filler particles, and the quality of the matrix / filler interface.

Abstract: The main objective of the paper was to prepare eco-friendly chiral hydrogels from chitosan and betulinic aldehyde under ultrasonic radiation effect, targeting their use for enantiomeric separations. This strategy promoted the obtaining of the hydrogels by supramoleclar organization of the imine units bonding the betuline skeleton with chitosan into ordered clusteres, while not altering the physico-chemical properties of the reagents. FTIR, SEM, CD spectroscopy and POM techniques were used to prove the pelicularities of the hydrogelation mechanism under the ultrasonication. The stability of the hydrogels was investigated by monitoring the influence of the swelling in three media of diferent pH, by POM and CD. It was concluded that the chiral hydrogels prepared by ultrasonication are stable when the pH vary from acidic to basic, indicating the new synthetic approach as a valuable method to yield suitable materials for enatiomeric separations in medical field.

Abstract: Polypropylene fiber is widely used as a reinforcing material in composite materials of various engineering projects, because it has high strength and corrosion resistance. In this study, with the purpose of examine the impact of discrete polypropylene fiber on frost resistance of cemented soil, cemented soil treated with polypropylene fiber is used as the research sample. Firstly, the impact of curing time, fiber content and length on the strength of cemented soil has been considered. And then, the frost resistance characteristics of cemented soil reinforced by polypropylene fiber with the content of 0.5% have been investigated. The results show that with the development of curing time, the strength of cemented soil increases logarithmically. By adding an appropriate amount of polypropylene fiber, the strength of the specimen may be improved. In this study, cemented soil reinforced by polypropylene fiber 0.1% in content and 3 mm in length has the best reinforcement effect. After 21 cycles of freezing and thawing processes, a sharp decline in strength of cemented soil without fiber, and the strength loss ratio is up to 45%. There are cracks in the specimens, and some of the specimens have broken off. Differently, after 21 freeze-thaw cycles, the strength of the cemented soil with fiber decreased less, and the strength loss ratios are between 1 and 13%, and there are only small cracks on the surface of specimens. The results show that adding discrete polypropylene fiber is a suitable method to prevent the generation and development of internal cracks in the cemented soil during freezing and thawing, thereby improving the frost resistance. These results can be used as a reference for the application of cemented soil reinforced with fiber in seasonal frozen regions.

Abstract: By using molecular dynamics, this study evaluates and compares the diffusion coefficients of CH4, CO2, H2, N2 and O2 gas molecules through a polysulfone / carbon nanotube, polysulfone / graphene and polysulfone / carbon nanotube-graphene composite membranes. Mechanical properties of the composites were assessed by performing virtual traction tests and the Young’s moduli exhibits values between 2.59 GPa for polysulfone membrane and 3.87 GPa for polysulfone / carbon nanotube-graphene composite membrane. The latter is found to exhibit superior permeability and mechanical properties, making it a promising device for gas separation.

Abstract: Two different polyimide structures were synthesized by two-step polycondensation reaction in solution, in the first step using equimolar amounts of one of two aromatic diamine (DDM or MMDA) and one dianhydride (6HDA) in N,N-dimethylacetamide (DMAc) to obtain the poly(amic acids), followed in the second step by thermal imidization. In order to obtain novel polyimide/metal nano hybrid materials, conductive Ni/Cu nanoparticles were embedded on polyimide substrates, using laser ablation technique. The morphology of the resulted thin metal layers was investigated using atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The results highlighted different surface characteristics of the auto-organized metallic/polymer nanoparticles, depending on the chemical structure of the polyimide substrate, the parameters of the laser ablation setup, the deposition time, the type of the metallic target. The obtained features of these polyimide/metal nano hybrid materials can be employed as an indicator of the possibility of using them for potential applications as conductive circuits or substrates for adhesion control.

Abstract: Over the time, numerous studies have been reported describing successful pulmonary valve replacement, either with xenografts or allografts, performed in sheep model. In contrast, comparable results have not been achieved yet for aortic valve replacement in orthotopic position, which involves a more difficult surgical technique, high hemodynamic demands for the implanted valve and poor survival of animals undergoing this kind of surgery. To our knowledge, in Romania, these were the first orthotopic allogeneic aortic root implantations using the subcoronary technique, carried out by our team. We established feasible perioperative, anesthetic and surgical protocols, which will be used in future studies to evaluate the in vivo functional performances of decellularized valves compared with autologous adipose derived stem cells seeded valves. Therefore, a unique research core was created, which is currently the only center of this kind in our country, by joining a multidisciplinary team consisting of biomedical engineers, cardiovascular surgeons, anesthesiologists, cardiologists, pathologists, microbiologists and veterinarians, who will continue the research activity in the field of tissue engineering and translate experimental results into clinical activity.

Abstract: In the last decades as the need for high economical and technical efficiency items/applications became acute, lightweight, high strength and low-cost materials development and investigation emerged as a logical and promising course of action. With high potential for both military and civil sector, the ultra-high molecular weight polyethylene (UHMWPE) is considered a new class of material. Among this class, the Dyneema® HB26 composite is of most interest for the present study. The present paper focuses on the static and dynamic investigation of the HB26 mechanical behavior experiencing an out of plane compressive load. For experimental purposes, using a 15 mm thickness panel two types of samples (cylindrical and cubic samples) were processed. For compression test Instron Testing Machine and the Split Hopkinson Pressure Bar (SHPB) were used. The experimental tests were then compared against the numerical findings highlighting a good consistency.

Abstract: Because hyaluronic acid (HA) cosmetic gels are the most commonly used gels in the cosmetic industry, the purpose of this study was to develop a new gel formulation of HA in carboxymethyl cellulose sodium (Carmellose, CMC Na), prepared in three different ways and to characterize the gel obtained in terms of texture, pH, thixotropy and decide which preparation method is optimal for obtaining a cosmetic gel. The gel formulations were prepared by dispersing CMC Na in water and glycerol and mixing it in three different ways with HA (at the same time, after gelling and 24 h after gel preparation). The pH, rheological properties and texture of hydrogels were evaluated. The study demonstrated that the formulation prepared with CMC Na has higher viscosity and stability at a pH = 6-9. The viscosity depends on the preparation method of hydrogels, the highest values of the mechanical parameters were recorded in the formulation in which CMC Na and HA were added at the same time. The present study showed that the difference on the texture was realised by the used preparation method. In conclusion the preparation method of a hydrogel with CMC Na 4% and 1% HA has a significant influence on the texture profile and the viscosity characteristics.

Abstract: Although autologous bone graft is the gold standard in bone reconstruction, the limited volume, the morbidity associated with the donor site, the dificult modelling of complex forms and the unpredictable rate of resorption fuel the researches towards the development of alloplastic materials as bone substitutes.A new fiber reinforced composite (FRC) was developed using 35% combination of monomers bisphenol A glycidylmethacrylate [bis-GMA], urethane dimethacrylate [UDMA], triethylene glycol dimethacrylate [TEGDMA], ) and 65% E-glass fibers (300 g/mp). Sixteen (n=16) male Wistar rats were used for the study. The experimental group (n=12) received intrafemoral implants of FRC. The control group (n=4) received intrafemoral titanium implants. After one month and three months respectively, tissues adjacent to implants were histologically evaluated. The intensity of the bone tissue inflammatory reaction, as well as the presence of the osteoblasts and the newly formed bone on the implant surface were the main criteria assessed. The FRC material determined a similar tissue reaction to Ti specimens, at one- and three-months follow-up. Both materials, inserted in the medullary canal, were surrounded by a fibrous connective tissue capsule, which, as time passed, underwent intramembranous ossification process. Fiber reinforced composite may be considered a promising alternative to titanium implants in critical size defects reconstruction.

Abstract: The paper presents a numerical study regarding the mechanical response of the body of a freight wagon to the usual loads encountered during service. The main goal of the present research is to investigate the possibility to replace the steel walls of the wagon with walls made of laminated composites. In this way, the total mass of the wagon can be decreased, leaving room for supplementary load of goods. Finite element analyses of the wagon with steel walls is presented first, in order to show that most of the load is taken by the structure of the wagon, while the stresses in the walls are low. Further, composite plates with different thickness are studied to find the minimum value of thickness for which the displacements have values below a certain range. These thicknesses are further considered in the finite element analyses of the entire wagon with composite walls to investigate if the new walls significantly change the stresses in the vehicle structure. It was concluded that the replacement does not alter the stress state in the structure, and, consequently, it is a good solution for diminution of the total mass of the vehicle.

Abstract: Although a standardized hip joint prosthesis is a quick and easy solution to repair most diseases related to the hip joint, it never satisfies the patient`s personal needs due to the uniqueness of the human anatomy. Femoral hip stem geometry is one of the factors that have an important impact on prosthesis lifespan or the revision surgery frequency that occurs due to postoperative complications, such as impingement or dislocation after THR (Total Hip Replacement). In this sense, the development of a custom hip stem prosthesis starting from a standardized femoral stem can bring benefits to the patient in time, being able to reduce the failure percentage of THR. The purpose of this article is the development of a custom prosthesis based on patient`s CT (Computer Tomographic) scans in order to be 3D printed with biocompatible materials, being able to serve as a study model in both engineering and medicine. Also this study represents a first step in understanding how to apply the unique distribution of mechanical properties in human bone, in order to manufacture a hip prothesis that can mimic them.

Abstract: Specific heat and thermal linear expansion coefficient of epoxy composites reinforced with carbon, aramid, glass and hybrid fabrics with unfilled and filled stratified matrices were studied. The thermal measurements of specific heat were performed with Differential Scanning Calorimeter (DSC instrument) and those of thermal coefficient of linear expansion were realized with Thermomechanical Analyzer (TMA instrument). It was analyzed the influence of fiber orientation at various angles (±15°, ±30° and ±45°) and the effects of two types of filler mixtures added into polymeric matrix on the thermal behavior of composite materials. It was found that in case of epoxy matrix the added filler mixtures reduced its thermal coefficient of linear expansion and had an insignificant influence on specific heat. In case of epoxy composites reinforced with fabrics, the fiber orientation and fillers addition showed different effects on the investigated thermal parameters in dependence of the used reinforcement types.

Abstract: Determining the dynamic properties in the frequency domain of aircraft structural elements is a very important aspect taken into account nowadays by aircraft manufacturers. One of the helicopters most exposed element to structural vibrations is the rotor blade, thus making its construction and the material choice a very important decision. Finite element methods can be used to assess the vibrational properties of such elements, in order to prove their airworthiness. The main objective of the article is to study how the use of different materials affects the structural behavior of the helicopter tail rotor blade, with regard to the frequencies at which these structures are prone to vibrate. The blade profile is the NACA0012 symmetric airfoil used on the IAR330 helicopter tail rotor blade and the main objective is to identify the best inner core material, while highlighting the importance of polymeric materials.

Abstract: The low velocity impact response of hybrid epoxy composites reinforced with plain weave fabrics, ply orientation at various angles and filled stratified matrix was analyzed in this study. The hybrid epoxy composites were subjected to impact tests at 45J and 90J of energy levels with drop weight impact machine. The damaged areas were investigated by visual inspection of impacted and non-impacted surfaces and by tomographic images. It was found that the replacement of certain carbon inner plies with glass ones and the modification of fiber orientation improved the damage resistance of the hybrid composites with aramid outer layers subjected to impact loading at 45J of energy level.

Abstract: The amniotic membrane is a readily available biomaterial with an important potential for tissue regeneration in dermatology and ophtalmology, with anti-inflammatory and anti-microbial properties. The extracellular matrix of the amniotic membrane is composed mainly of collagen, fibronectin and laminin. The purpose of our study was to investigate the structural modifications of collagen extracellular matrix of amniotic membrane upon interaction with two different antibiotics, frequently used in surgical and post- surgical procedure, respectively ciprofloxacin and gentamicin. SEM micrographs evidenced the ultrastructure features of dried amniotic membrane, with laminar structure, flexible, transparent, with no blood vesels or nerves. FTIR spectroscopy combined with deconvolution techniques was applied with the aim to determine the extent of denaturation upon treatment with different antibiotics. By spectral analysis, we concluded that gentamicin treatment is more favorable compared to ciprofloxacin, as the denaturation process is reflected by the lower sheet/turns ratio of the secondary structure composition.

Abstract: Expanded polystyrene (EPS) is used in a variety of applications due to its characteristics, light weight, good thermal insulation and durability. Expanded polystyrene, when used to insulate buildings, undergoes various mechanical stresses, such as: compression stresses, bending stresses, dynamic stresses or shock stresses. This paper presents the results of three-point compression and bending tests for four types of polystyrene (EPS-50, EPS-80, EPS-100 and EPS-120) at different speeds. Based on the data resulting from the compression tests, the theoretical mathematical model was determined, which can be used both for determining the theoretical mechanical characteristics and for modelling the EPS properties in numerical simulations.

Abstract: The paper deals with destructive testing of “new” group of material - Wood Plastic Composite (in short WPC). WPC emerging from a fusion of two different kinds of components - thermoplastics matrix and natural reinforcement (fibres or flour). Natural fibres offer several advantages - they are renewable, inexpensive, low-density, good isolate a sound and low cost. These components are mixed under the influence of high temperature and then pressed to make various shapes. This material contains cracks localized on the interface between the wood and plastic. These cracks occurred due to inhomogeneity of WPC and affected mechanical properties of final WPC product. The testing of mechanical properties (tensile test and bending test) were determinate in VUHZ Dobra (Ostrava) - following the ISO standards. Significant differences between mechanical properties after testing were caused by non-perfect encapsulation between components and non-homogeneity of materials.

Abstract: The additive manufacturing technology has made its debut in the industrial field about 30 years ago, when prototyped parts were usually used at the 3D printing stage during fabrication, to give the end customer a truthful concept of how a part will looks when conventional manufacturing techniques were used for final part fabrication. Because of the increasing demand for non-toxic, biodegradable materials and products, human society is always searching for new materials with specific applications, which are able to fulfill the above-mentioned requirements. Consequently, it is essential to identify the qualities of these materials and their behavior when subjected to various external factors, in order to find their optimal solutions for application in various domains. Manufacturing parts from biodegradable materials by 3D printing represents a major concern of industry specialists. The 3D printing process involves several parameters whose influence on the sample functional characteristics is a topical issue. In this paper are determined influences of certain technological parameters (thickness of the layer, filling speed, and part orientation on the printing bed) on some mechanical properties (tensile strength, structure, thermal analysis by DSC, and friction coefficient). Experiments were performed on specimens made of three materials: PLA, HD PLA Green, and Impact PLA Gray. A complete factorial experimental plan was used with three input parameters on two levels. Each experiment was repeated three times following the process stability. The obtained mean values of the tensile test were used in the analysis. The analysis was performed with the MiniTab application, which allowed the parameters hierarchy by influencing each mechanical characteristic studied, model development, and optimum values setting.

Abstract: The paper aimed to reveal, qualitatively and quantitatively, the modifications suffered by the PLA during the complex heating cycle specific to the 3D printing followed by laser marking. The obtained results showed that the melting point of the PLA decreases from 162.2oC (which is specific to PLA filament) to 153.1oC after the 3D printing process and to 149.7oC after the laser heating. The glass transition suffered the same lowering after the printing process but an important increasing after the laser heating. The elastic modulus evolution proved a decreasing of the plasticity and that is hapenning when the material suffers an increasing of its rigidity. The elongation viscosity was analyzed and its values were decreasing with the increasing of the temperature that happened on the material. The decreasing was produced by the reduction of the elasticity, when the chain branches are decreasing their length. The decreasing is more pronounced with the increasing of the temperature. The ratio between the loss modulus to the storage modulus and quantifies the way in which the PLA absorbs and disperses energy moves its peak from 65oC (curve specific to the PLA filament) to 45oC (curve specific to the last layer deposited by 3D printing process and re-heated by laser beam for marking). The peak means the lowest storage modulus, which is a measure of elastic response of a material, so the transition from glass to high elasticity moves to the lower temperatures.

Abstract: Bisphenol-A (BPA) is widely spread among the endocrine-disrupting chemicals (EDCs). Different hormone derivates or various organochlorinated pesticides are industrial human-made “plastics.” EDCs are ubiquitary used in the modern world, and their impact on human health has been intensively studied in the last decades. BPA is used as a representative model for endocrine disruption mechanisms; it represents a critical element of producing polycarbonate plastics and epoxy resins, necessary for the manufacture of beverage or food containers, various personal-care products or dental industry products. Environmental exposure to BPA or other EDCs has resulted in functional or morphological drastically alterations of the genital tract or mammary gland that lead to earlier onset of different diseases, reduce fertility, or inducing prostate cancer. All the above have been observed via multiple in vitro analyses on human cells or in vitro analyses on animal models, especially rats. BPA causes prostate cancer through a sum o mechanisms. It increases the activation of various signaling pathways (Erk or Akt kinase), steroidal receptors recruiting chromatin, derived activity of different histone-modifying enzymes, transcription of various androgen receptor mutants detected in prostate cancer or acting via a pro-inflammatory mechanism that leads to prostate cancer progression once installed. Other EDCs such as different dioxins, cadmium, or inorganic arsenic are also incriminating in the neoplastic transformation of the prostate. This review aims to evaluate the current knowledge on this topic. Most of the authors agree on the carcinogenetic effects of these compounds. Extensive in vivo research on humans is imperative for a better and more accurate understanding of “plastics” impact.

Abstract: In this paper it is presented a comparative theoretical study - performed by finite element analysis (FEA), of the tension state that appears at the level of the spine, as well as in the areas adjacent to it, under the following conditions: a) the existence of a comminutive fracture at the level of the vertebra T11; b) of the external immobilization of the body through a Lombax orthesis (LO) or of the internal immobilization of the column by means of a spinal fixator (SF); c) of performing some basic flexion or extension movements. In this study, both flexural force and extension force varied on three levels. The results of the comparative theoretical study were supplemented with the clinical observations obtained from a number of 52 patients who had suffered comminutive fractures in the T11 vertebra and who were treated - by external immobilization, in the Lombax orthesis or were surgically treated - by applying a trapped spinal fixator on the T10-T12 vertebrae. The study had demonstrated that, by immobilizing the body in the Lombax orthesis, following the application of the flexion or extension movement, the mobility of the body is low, the bone fragments move less distances by about 12% against to their displacement under the condition of immobilizing the column by a spinal fixator. Although, in the latter case, the displacements of the bone fragments are greater, the elastic behaviour of the spinal fixator determines the returning of the fragments and of the spine to the initial position as well as the distance between the vertebrae. Clinical investigations on patients treated by external immobilization of the body in the Lombax orthesis show that the values of the local kyphosis angle (LKA) are about 30% lower than the values of the same parameter obtained under the surgical treatment.

Abstract: The concept of ballistic protection is a subject of great importance and is defined as representing all the capabilities of the military vehicle to withstand attacks, in order to ensure protection of the crew during the missions. The projectile-plate impact research must answer a series of questions on designer or fighter behalf, among which the most important would be whether the bullet penetrates or perforates and whether the velocity after the perforation ensures a lethal effect on the personnel. The current paper presents the numerical evaluation of the working together of aluminum layers with plastic materials in a multilayer structure with honeycomb core, on impact with a rigid projectile. Plastic materials have revolutionized many industries and they are increasingly used due to their main properties, low mass and high strength. The research included the use of plastics, the positioning within the panel and the study of the two constructive versions of the structure, with coupled and uncoupled layers. Post-processing model and interpretation of the results are offered and these could be enriched and customized for other situations, similar or less similar, implicitly, the method is provided, finding a quick answer to certain questions.

Abstract: With a wide range of composite resins available today, clinicians can benefit from knowledge of the infrastructure of a particular material in order to determine which type will work best in a specific clinical situation. The purpose of this study is to analyze the biomechanical behavior of four types of composite resins, two of them used in direct restorations and the other two for prosthetic restorations created in the lab.The deformations, hardness and elasticity were analyzed under the same conditions, namely at 200 Mpa, as these are very important parameters for the biomechanical behavior of the analyzed biomaterials, the specificity elements being correlated with the biomaterial structure, polymerization time and polymerization modality. As a synthesis of the biomechanical behavior outcome related to the used resins versus the resins used in the lab of dental technique using indirect means, a relatively wide range of higher value parameters stands out with regard to resistance for the lab composites compared to those used in direct restorations.