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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.

The search for green composite for sound-absorbing material has increased a significant interest. In this study, polystyrene (PS) composite foam filled with primary sludge and boiler ash from pulp mill was produced. The product was characterized using analytical techniques such as FTIR, XRD, SEM, TGA, and DSC, while the mechanical properties and sound-absorbing coefficient were analyzed regarding ASTM D 2240 and ASTM E-1050-98, respectively. The results showed that the sludge has 1β crystalline polymorph cellulose from the pulp. The chemical reaction can be seen by the chemical bond formed during the mixing process. The peak expansion occurred at 1600.44 cm-1 indicating the presence of a C=C functional group of maleic anhydride with polymer and filler. SEM images showed that the filler was distributed and dispersed into the polymer matrix and no agglomeration was produced. The sound-absorbing composites had complied ISO 11654:1997 regarding the sound absorption coefficient rating level on materials for rooms with sound absorption classes D and C with the value of α 0.328-0.793.

This study was geared to analyze the preparation methods of pullulan acetate-based nanoparticles loaded with 5-fluorouracil, as well as the potential of pullulan as a biopolymer matrix for obtaining nanoparticles applied in the delivery of anticancer drugs (5-FU). Various methods were used to produce pullulan acetate-based nanoparticles loaded with 5-FU, including nanoprecipitation, modified nanoprecipitation, and double emulsion. Pullulan was previously chemically modified with acetic anhydride, dimethylformamide and pyridine, and yielded pullulan acetate. Pullulan was made using the Aureobasidium pullulans strain through a fermentation procedure. UV-Vis Spectro-photometric and dynamic light scattering (DLS) methods were used to assess entrapment effectiveness, size, and polydispersity index (PDI) of pullulan acetate-based nanoparticles loaded with 5-FU. Based on the properties of the nanoparticles obtained, the optimum preparation method was chosen. The maximum entrapment efficiency was found in pullulan acetate nanoparticles loaded with 5-FU generated by a double emulsion method. The mean hydrodynamic size and PDI of all nanoparticles were adequate. The best formulation showed faster 5-FU release profile in acid phosphate-buffered saline (pH 5) than in phosphate-buffered saline pH 7.4. According to the findings, pullulan derivatives have a great potential for producing nanoparticles that might be used to deliver anticancer medicines.

Intended to draw a frame of the impact of plastics usage and the role of the circular economy, this paper relied on specific literature, data from different studies, case studies, reports and databases existing on the research area. Being produced at low costs and used in a wide range of fields, plastics has been confirmed as one of the most impactful inventions for human. Recently, during the pandemic years, plastics has gotten multiple usages, such as keeping a hygienic sanitary environment facing the critical situations, with a highly increased role in the fight against the SARS-COVID-19 crisis. It is also well known that plastics presents risks arising from its production flow, linked to a huge degree of massive pollution with high impact on the environment. Plastic waste exposed to the environment generated problems and it is of huge concern for all forms of life. As plastics products are present all around the world, there is an increasing statement to one-use plastics in the environment. Thus, it is urge to take actions for managing this situation as appropriate, to protect the environment and reduce the consumption of plastics, which can be achieved by developing and sustain the circular economy, as a new research field to explore. Through this paper we intended to emphasize the importance that, both theoretical contribution and practical measures, have on the production, the use and recycling of plastics and on the circular economy.

The recycling and high-valued added reuse of automotive plastics have elicited global attention as the number of end-of-life vehicles increase. In the paper, the two-stage high-voltage electrostatic separation is used to explore the sorting of passenger vehicle plastic mixtures of PP, ABS and PVC. The purities of PP, ABS and PVC are all higher than 97%, and the recovery rates are 55%, 93%, and 48%, respectively. Taking PP plastic as an example, the mechanical properties of the recycled materials and the different ratios of recycled and new material mixtures are studied. Results show that the passenger car bumpers reproduced with a 7:3 ratio of new and recycled materials can satisfy the performance requirements. The finding provides a reference for the high additional value reuse of other automotive plastics.

Purpose was to determine the viscoelastic properties of three root canal sealers as a function of temperature, time and frequency using dynamic oscillatory measurements. Methods: Measurements were performed on the dynamic oscillatory rheometer set to temperatures: 25°C, 35°C, 40°C and 65°C. Stress sweep and frequency sweep tests were used in order to determine storage moduli G’, loss moduli G’’ and complex viscosity η*. Results Higher values of storage compared to loss moduli indicate the more pronounced solid-like behavior of tested materials. EndoREZ showed the highest values of G’ and G’’ moduli at all temperatures. With temperature increase the G’ and G’’ moduli of Sealapex and EndoREZ increased while the moduli of AH Plus decreased. With frequency increase all materials showed viscosity decrease exhibiting non-Newtonion, shear-thinning behavior. With temperature increase AH Plus demonstrated viscosity decrease, while the viscosity of Sealapex and EndoREZ increased. Clinical significance: All tested materials were temperature, time and frequency dependent and this dependency varied between them. The obtained results may be used to predict the rheological behavior of root canal sealers in different temperature conditions, thus helping as to estimate optimal handling characteristics for specific clinical applications.

Atherosclerosis can affect the blood vessels in any region of the body and the stenosis (narrowing) can be located on an artery that vascularize important organs, such as the brain, abdominal organs or limbs. The endovascular surgery is a modern approach to vascular pathology through minimally invasive techniques (puncture, minimally vascular approach) and it represents an enrichment of the arsenal of surgical techniques and brings considerable improvements in post-operative and long-term outcomes The use of polymer drug-coating balloons is an attractive alternative because they can offer the promise of an improved patency compared to the simple balloons and a reduction in the need for stents. The aims of this study were to describe the polymer materials and to compare the medical endpoints obtained in angiosome-targeted infrapopliteal angioplasty using a simple balloon with two layers, based on polyethylene, and respectively a drug-coated balloon that contains a multiblock copolymer from polyethylene, poly(cylohexylethylene), polyisoprene and poly(1,3-butadiene) covered by Paclitaxel. The balloons were characterized by differential scanning calorimetry, stress-strain and puncture tests in order to describe their physical and mechanical characteristics. On the other hand, 51 patients with critical limb ischemia were treated with different balloon angioplasty and they were monitored for 12 months after the intervention; the following parameters have been evaluated: diabetes, hypertension, renal insufficiency, hemodialysis, stroke, dyslipidemia, heart disease, heart failure, body mass index, number of angiosomes, creatinine, and wound healing, leg salvage and amputation-free survival at 1, 2, 3, 6, 9, 12 months. Significant associations were found in the case of anterior-tibial-artery and posterior-tibial-artery angioplasy and the age, hypertension and renal insufficiency. On the other hand, the results indicate that the drug deposition on the surface of the balloons lead to improved values for the observed medical endpoints. In conclusion, this study reveals that angiosome-based infrapopliteal angioplasty with drug-coated balloons can be associated with better wound healing and leg salvage.