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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.

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.

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.

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.

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.

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.

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.

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.

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.

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.