Volume 61, Issue 4

Abstract: Wooden resistance elements, such as beams and pillars, are often used in construction. They must be designed and made so as to withstand the loads to which they are subjected during use. The predominant stress of the beams is bending, the maximum values of normal stresses due to the loads that solicitate the beams being important to know for ensuring its bearing capacity. In this paper an experimental study is presented regarding the resistance elements of the beams type. The beams are made of two types of wood, namely beech wood and poplar wood, having a rectangular section. These beams were reinforced with composite materials based on carbon fiber such as plates and fabric that were applied to the beams with the help of an epoxy resin, in order to study their behavior when subjected to bending stress. Bending tests were made until the beams were damaged, measuring, in this sense, the applied forces and the related displacements. The strength of wooden beams reinforced with composite materials was compared with the strength of wooden beams without the addition of composite material, thus establishing which is the better constructive reinforcement solution, for the two essences of wood, to ensure safety in operation, in construction field.

Abstract: Nowadays, Manufacturing and automotive industries have begun to employ renewable resources as a result of public awareness and rigorous legal requirements relating to the usage of polymers. This study has focused on employing Snake Grass (SG) fiber as reinforcement in Aegle Marmelos with Epoxy blended hybrid matrix (AME), since natural fiber reinforced composites provide a significant role in the development of lightweight structural components. The primary study investigated the effects of fibre length and fibre volume percentage on the mechanical properties of snake grass fibre. Based on the test results, the composite with a 15 mm fibre length and a volume percentage of 20% SG fiber has better mechanical qualities. Finally, mechanical and dynamic mechanical properties are used to assess the impact of Aegle marmelos with Epoxy blended hybrid matrix addition into the snake grass fibre composite. The inclusion of natural fiber with epoxy matrix and natural (Aegle marmelos) filler increased composite characteristics due to their synergistic effect. This enhances the adhesion and stress transmission uniformity between the reinforcements. The morphology of the fiber surface is assessed using micrographs acquired with a scanning electron microscope.

Abstract: A new bicomponent hybrid material was obtained by encapsulating quercetin in PLGA using solvent evaporation method. The morphological aspects of the samples were established by scanning electron microscopy (SEM). Particle size distribution was determined by dynamic light scattering (DLS), numerical distribution showing that the particles are micrometric, with two granulometric intervals: [385-479] nm and [662-918] nm. Morphology was typical for PLGA, spherical one; the obtained particles are porous with micrometric pores. Zeta potential (ZP, -4.84mV) showed that the particles have electronegative surface charge. The loading efficiency was determined spectrophotometric and it was 18.3% in the mentioned synthesis conditions.

Abstract: This study aimed to compare the impact of thermal cycling on the flexural strength (σfs) of 3-dimensional (3D) printer resins and polymethyl methacrylate (PMMA). It also aimed to evaluate different surface treatment protocols and surface sealant applications on the surface roughness (Ra) and surface hardness (VHN) of the resins used. Rectangular (25×2×2 mm) and disc (Ø10×2-mm) specimens were fabricated from auto-polymerized PMMA, and 3D-printed resins were tested for mechanical properties (ISO 10477) using thermal cycling (n=10). Disc specimens were separated into three groups (n=10) based on the surface treatments: conventional sanding (C), disk polishing (P), and surface sealant coating (O). Ra and VHN values were statistically analyzed with the Kolmogorov Smirnov, Shapiro Wilk, Independent Samples t-test, Mann-Whitney test, one-way ANOVA test and Kruskal Wallis test (α =.05). A significant main effect was found on the flexural strength analysis for each of the two factors: thermal cycling procedure (p[0.001) and materials (p 0.001). A significant main effect was found on the surface roughness and hardness analysis for each of the two factors: surface treatment protocols (p[0.001) and materials (p[0.001). Based on the results; interim materials produced with 3D-printed resins have better mechanical properties than conventionally polymerized materials. Coated materials had lower surface roughness values than polished ones, and adding a surface sealant agent increased their hardness significantly.

Abstract: The study investigates the effects of aggressive factors environments commonly found in industrial environments on the elastomeric material TPU 95 A, which is integrated into a multitude of soft robotics applications. Specimens made of TPU 95 A were subjected to aggressive liquid media - cooling oil, distilled water, and ultraviolet radiation (UV-C) to evaluate changes in their mechanical and elastic properties following uniaxial tensile tests. The research, carried out using additive manufacturing technology, highlights the importance of monitoring how the external factors impact elastic and mechanical characteristics of TPU 95 A material. The results obtained after the experimental tests proves to us that the aggressive media analyzed had a greater or lesser influence on the material. By uniaxial tensile tests, it was found that the liquid absorption had a very important impact on the tensile strength of the material. For example, at 1.02% absorption in distilled water, the maximum value of the ultimate strain decreased by 0.257 mm/mm, and at 3.06% absorption in cooling oil, the maximum value of the strain decreased by 0.672 mm/mm.

Abstract: Using propylene-ethylene block copolymer (PPB) and metallocene polypropylene random (mPPR) as matrix, olefin block copolymer (OBC) and metallocene polyethylene (mPE) as reinforcement, trimethylolpropane trimethacrylate as sensitizer, antioxidant 1010 and dioctadecyl 3,3-Thio-dipropionate as antioxidant, the radiation-crosslinked polypropylene with excellent high-temperature performance was prepared by one-step process and it was used to produce the heat shrinkable tape with three layers structure further. The effect of the formula, the orientation, the crosslinking, the heat treatment and shrink on the crosslinked-polypropylene were studied. The results show that the crosslinked-polypropylene has optimum overall property when the amounts of PPB, mPPR, OBC, and mPE were 50, 10, 15, and 15 phr, respectively. After the orientation in one-step process and the radiation crosslinking with the irradiation dose of 6 Mrad, the tensile strength, the elongation at break, the shrinkage ration, the gel content of the crosslinked-polypropylene reached 33 MPa, 390%, 30%, 51%, respectively. After heat treatment, its mechanical properties further improved and the decrease of its tensile strength and elongation at break did not exceed 15% after thermal ageing at 130 oC for 100 days. Moreover, the corresponding heat shrinkable tapes show outstanding peel strength, impact strength and cathodic disbondment properties in various conditions.