Browse Articles

The PPR pipes are more and more used in different industrial applications, due to their multiple advantages compared with the conventional metallic pipes. The experimental study presented in this article, was conducted in two directions, analyzing the behavior of welded PPR pipes and also the behaviour of unwelded PPR pipes exposed to different aggressive environments. In the second investigation, the PPR pipes were immersed in different chemically active environments as gasoline, sodium hypochlorite (NaClO), water + sodium hypochlorite (NaClO)-20% NaClO volume concentration, for a period of 3 weeks (21 days), in order to reveal the influence on the mechanical properties of the PPR pipes. The examination was made by using both visual inspection and tensile and bending tests. The investigations made have led to the conclusion that the presence of sodium hypochlorite do not affect the mechanical properties of PPR pipes, unlike the gasoline which significantly decrease the yield stress value. For the welded PPR pipes it was found that they failed at pressures of about 180 bar. Although the optimal welding parameters, recommended by the manufacturer, were modified (maintenance time), the only sample that failed in the welded joint was the one with the most acute misalignment and the shortest welding time. However, the sample withstood high pressures, reaching about 55% of the burst pressures obtained for welded pipes with the recommended welding parameters. The need to conduct such studies derived from the fact that most of the information regarding the behavior of PPR pipes is provided by the manufacturers and there is insufficient information in the scientific literature.

Boswellia seratta (BS) is the best herbal medicine to treat Rheumatoid Arthritis (RA), due to its anti-inflammatory and anti-arthritic activity. Delivering BS through an oral drug delivery system has been in effective, because of its enzymatic degradation within the Gastro-Intestinal (GI) tract. In this paper, we develop a gastro retentive approach for delivering BS to avoid high hepatic first pass metabolism and optimized buccal patch based on the drug delivery characteristics. There are seven different formulated buccal films of BS that were prepared by the solvent casting method, using mucoadhesive polymers, Poly Vinyl Alcohol (PVA), and Sodium Carboxy Methyl Cellulose (SCMC). These with drug formulation can be represented as PCB. The prepared films were evaluated by various physicochemical properties and characterization studies. Results obtained from physico-chemical properties, in-vitro and ex-vivo studies among all seven patches, PCB5 shows better drug-releasing characteristics. This was further confirmed by FT-IR and XRD characterization studies. Also, the data was statistically analysed using Analysis of Variance (ANOVA).

Novel block biocopolymers were made by copolymerizing the prepared polylactide-dipenta-erythritol macromonomer with two different monomers, N-hydroxyethyl acrylamide (HEAA) and N,N-dimethylamino ethyl methacrylate (DMAEMA), with an activator generated by atom transfer radical polymerization (ATRP), to have a different duplicating unit of 10, 25, 50, and 100. ATRP employs a copper(I) bromide (CuBr) catalyst system with N, N, N′, N′′, N′′-pentamethyl diethylenetriamine (PMDETA). Different spectroscopic and analytical methods used for characterization of the prepared biocopolymers, such as FT-IR, 1H NMR, 13C NMR, and GPC, showed that they had narrow dispersity with controllable molecular weight and were accompanied by nanostructures as examined by SEM technique on all biocopolymers, confirming the correctness of the expected structures of biocopolymers. The shape and size of the produced polymeric nanoparticles were determined using a scanning electron microscope (SEM), and they were developed using the Image-J application.

The timber industry takes an important place in our modern life, and there has been an increased interest in it for a long time, especially in industrially developed countries. The concerns of the environmental organization regarding the plant wealth preservation have caused scientific trends to search for sources or industries that can achieve acceptable alternatives to natural wood. The materials in this article are related to industrial timber manufacturing of greenhouse wood waste, low density polyethylene and non-standard joinery waste. Moreover, panel samples made from the above materials were briefly subjected to tests as well as tested by fresh and salt water absorption.The density calculation results for all samples have shown the possibility of obtaining a wide range of wooden planks from the lightest to the heaviest ones, depending on the type of filler used. Additionally, the conducted research has shown the possibility of producing artificial wood panels made from the studied materials with good quality and fully satisfactory physical and mechanical properties.

Every day, the need for composite materials grows. The physical and chemical characteristics of the constituent materials inside the hybrid composite impact the final structure. The rate at which these individual properties are sustained varies, but it has an impact on the final properties of hybrid composites. Sporting goods and lightweight orthopaedic components are made from hybrid composites. Glass fibre epoxy and sawdust are utilised to construct hybrid composites in this study, using glass fibre to epoxy resin ratios of (60:40, 60:39, 60:38, 60:37).The current research involves the creation of hybrid composites and their study for flexural and tensile strength under various load conditions. Applying resin and hardener, as well as inserting reinforcement, is repeated in the hand-layup manufacturing process to improve characteristics and create a laminate form. They improve fatigue and fracture resistance while providing dimensional stability and weight savings.

The purpose of the present research was to assess the effect of three different fresh detox juices on the color stability of the resin composite with three different adhesive systems. Disc-shaped resin composite specimens were prepared. Composite discs were randomly divided into 3 subgroups according to the adhesive system (Adper EasyOne, BondForce, Clearfil QuickBond), adhesive system was applied to the upper surfaces of the composite discs according to the manufacturer`s instructions. The first color measurements were made with a spectrophotometer after the composite discs were kept in water for 24 hours. Samples in each group were divided into 4 subgroups according to the immersion solution (n=10; brands, water). The samples, which were kept in respective detox juices, were kept for 10 minutes twice a day, at other times they were kept in distilled water. Second color measurements were performed 30 days later. Data were analyzed with two-way ANOVA and Tukey HSD tests. According to the two-way analysis of variance, the adhesive system does not affect the color change significantly (p=0.773), but the detox juices has a significant effect on the color change (p=0.01). Fresh detox juices may adversely affect the color stability of adhesive systems, regardless of their color, but this effect may not be expected to be clinically observable.

Research on crack propagation for fiber reinforced composites containing flame retardant is rare. The micro-cracks propagation is a reason for delamination and debonding failure of fiber reinforced composites. To study the crack propagation of continuous glass fiber reinforced epoxy resin laminates that contained ammonium polyphosphate flame retardant (GFRP-APP), the quasi-static single-edge tensile loading (SETL) experiments for the end-notched GFRP-APP specimens were carried out by MTS universal electronic testing machine. The crack propagation of the end-notched 90° GFRP-APP specimen includes two types, both of which belong to opening type (mode I). Namely, one type is mode I multi-cracks propagation without preexisting crack, and the other is mode I fiber bridge propagation with preexisting crack. The intralaminar fracture toughness along fiber direction of GFRP-APP is approximately 8.4 N/mm, which is calculated by area method. The opening displacement-tensile force curves can be divided into three stages for 90° GFRP-APP specimen without crack, i.e., crack gestation, crack birth and crack propagation. However, the 90° GFRP-APP specimen with crack not contains the crack birth stage. Additionally, the microscopic morphology for the fracture face of pure epoxy resin and GFRP-APP, and the phase analysis for GFRP-APP were performed by scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). As a conclusion, the pores and interfaces in materials were the guiding factors of micro-crack propagation, and the ammonium polyphosphate flame retardant particle contributed extra interfaces.

At the moment, the tendency in the composites field, is to use natural resins and fibers to obtain „environmental friendly” materials, that are compostable and biodegradable. In this paper there is an experimental study of the depletion capacity of the vibration from the composite beams, using the hardener made of cotton, flax, hemp, silk textile and the three types of the Dammar hybrid resin matrix. The damping factor and the eigenfrequency of the vibrations was determined experimentally for these bars. Based on the acquired results, the dynamic elasticity modulus and the loss factor were calculated, for each composite material studied.

Highlighting the properties of polymer composites is a complex process given their great diversity and the wide range in which their characteristics could vary. An Artificial Neural Network model for predicting tensile strength was designed using LabVIEW software. The proposed model was developed for randomly reinforced polymeric composite materials with 30%, 40% and 50% fiber-glass. Volume fraction of glass fibre has represented the independent variable for this study. The dependence of the tensile strength on the volume fraction was investigated and highlighted by modelling using neural networks. The designed Artificial Neural Network behaves as a computational system that process data input into a desired output using a network of functions composed of layers. The training process was developed with different Artificial Neural Network architectures with two hidden layers to produce the best prediction results. For each hidden layer the number of neurons was varied be-tween 3 to 50.

The present paper analyses the possibility of using the digital image correlation technique to study the mechanical behavior of small scale components. A microscope is supplemented to the equipment for magnification, together with a miniature tensile testing machine. Several samples with already studied stress concentrators were analyzed. For comparison purposes, a finite element model of the geometry, with appropriate loading conditions, is created and the strain field is compared, in orderv to be validated to the experimental one. Results show that an accurate reading can be made by using this technique. Furthermore, crack initiation and its propagation path can be determined, by the appearance of high strains in the region.