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The paper presents a study on the stresses and deformations induced by the transversal loading of some flat plates made of E Glass EWR Fiberglass Woven Roving type, having delamination type defects. The parametric analysis of the delamination influence on the stresses and displacements occurring in the plate material is performed. The results of the static calculation are compared with the experimental tests of the flat plates subjected to bending, highlighting the concordance of the variation of the stresses and displacements versus to the position of the delamination position.

In order to investigate the mechanical properties of polyurethane cement (PUC) composite materials, axial tensile test, acid and alkali corrosion resistance test, bond test with concrete, and bond test with steel bars were conducted. The axial tensile results show that the tensile strength of PUC material is 31.11MPa, the stress-strain curve for axial tensile behavior of the material is obtained through fitting. To explore the durability of PUC materials, acid-alkali-salt corrosion resistance test is carried out, the results show that the PUC material has good resistance to acid and alkali corrosion. The failure mode of the bond test between PUC material and concrete is internal cohesion failure of concrete material, indicating good bond performance of PUC material. Axial tensile test of PUC material is carried out at different temperatures (-40℃~60℃). When subjected to temperatures between 40°C and 60°C, the strength of materials does not deteriorate. However, it is noteworthy that the material’s ability to withstand tensile strain significantly increases as temperatures rise to 60°C. The bonding strength between PUC material and steel bar increases with an increase in protective layer thickness, and at a thickness of 70 mm, the maximum bond stress is achieved at 16.38 MPa. On the other hand, the strength of the bond reduces as the anchorage length increases. Smooth round bars demonstrate a significantly lower bond strength compared to deformed bars, as their maximum bond strength is at approximately 47.4% of that of the deformed bars under the same conditions.

The paper presents the characterization of 5 polymer composite materials with a poly-propylene (PP) matrix obtained with different (mass) concentrations of strontium ferrite (Fe12SrO19) reinforcement that have synergistic protective properties against electrostatic discharges (ESD) and electromagnetic impulses (EMI). These types of composites can be used to protect electronic equipment. To this purpose, suitable polymer composites were developed using SrFe12O19 type filler in two forms (powder and concentrate). The weight ratio of the PP/SrFe12O19 composites obtained by the extrusion process and injection from the melt is 75/25 and 70/30. The characterization of these composite materials consisted of carrying out some physico-chemical tests to determine the hydrostatic density and the resistance to the action of water, as well as FTIR, UV-Vis analyzes and dielectric, magnetic and functional tests to identify the simultaneous protection performance at electromagnetic shielding and electrostatic discharges, which can occur in the electro-technical, electronics and automotive industries. It is also found that all composite materials presented reflection shielding properties (SER) in the range: -71.5 dB...to -56.7 dB, indicating very low absorption shielding. The best performing material was the PP/SrFe12O19 powder composite with a weight ratio of 70/30. At the same time, EDS tests were also carried out on these materials. For these applications, the surface resistance Rs and the point-to-point resistance Rp were tested. Recommended composites for simultaneous EMI and sensitivity to electrostatic discharges (ESD) functionality, in order of their performance, are M2 (with 30% ferrite powder) and M1 (with 25% ferrite powder). M4 composite (with 30% ferrite powder concentrate) can also be used at the limit. Following the research carried out, the obtained results recommend the composite with promising simultaneous operations as M2 (with 30% ferrite powder). The element of originality consists of obtaining polymer composites with simultaneous properties of protection against electromagnetic impulses and electrostatic discharges.

This study investigated the mechanical and sensing properties of ethylene-vinyl acetate (EVA)/carbon nanotubes (CNTs) composites in both film and fiber forms. The incorporation of aligned CNTs in the composite fibers possess improved mechanical properties and enhanced sensing performance compared to those of composite films with randomly dispersed CNTs. Thermogravimetric analysis revealed promising thermal stability, indicating potential applications for long-term usage. Cyclic tensile testing demonstrated that the fiber samples with better CNT alignment exhibit higher sensitivity, emphasizing the significance of CNT orientation in constructing an efficient conductive network for strain sensing. Considering the contribution of the CNTs` orientation along the measuring direction, a model contains modification parameters was proposed, where a master curve was given, revealing the ideal potential of the EVA/CNTs composite fiber with perfectly aligned CNTs. This work provides valuable insights into the influence of CNT alignment on the mechanical and sensing properties of EVA/CNTs composites. The results underscore the importance of optimizing CNT orientation for enhanced sensing performance in various engineering applications.

As an environmentally friendly and renewable energy solution, wind power is rapidly gaining favour worldwide due to its gentle impact on the environment. Nevertheless, the potential environmental risks posed by discarded wind turbine blades still need to be brought to our attention. Therefore, exploring ways to recycle and reuse discarded wind turbine blades has become an urgent task in the field of environmental protection. This study focuses on the incorporation of recycled glass fibres from crushed wind turbine blades into concrete to assess their benefits in engineering practice. In this study, we used four different particle sizes of recycled glass fibres, 0-5mm, 5-10mm, 10-15mm and 15-20mm, and incorporated them into the concrete at four different admixture levels of 0.2%, 0.4%, 0.6% and 0.8%. By comprehensively examining its workability, mechanical properties and microstructure, we found that although the incorporation of glass fibres reduced the apparent density, slump and compressive strength of the concrete to a certain extent, it significantly improved the split tensile and flexural strengths of the concrete, as well as effectively improved the brittleness of the material and enhanced its toughness. These findings reveal the feasibility of recycling glass fibres from decommissioned wind turbine blades and applying them to concrete. This study not only opens up a new path for environmentally friendly recycling and reuse of wind turbine blades, but also provides a valuable reference for practical engineering applications, with significant social and economic benefits.

The elaborated paper presents a series of methodologies with which the dynamic characteristics (damping coefficient, damping factor) can be determined, depending on the working conditions, of a hyperelastic material using vibration theory. These methodologies can be extended to characterize any type of hyperelastic material. The main aim of this work is to develop experimental technology and methodology to characterize this type of materials like rubber to establish a series of dynamic factors like damping factor, transmissibility at resonance, pulsation at resonance, dynamic elastic constant. These characteristics are variable, depending on composition, request, etc. In conclusion, they are not available in specialized literature as are the characteristics of linear-elastic materials. The application of numerical calculation programs in carrying out resistance calculations, in the case of structures made of such materials, is also impossible to achieve, having as an impediment the lack of knowledge of the values of the material characteristics.

To optimize the infill parameters and improve the tensile properties of 3D printed polyethylene terephthalate-1,4-cyclohexanedimethanol ester (PETG) models, this study explored the effects of infill thickness, infill flow rate, and infill overlap length on the tensile properties of 3D printed PETG models via the one-way test combined with the Taguchi test. The results of the one-way test showed that the tensile strength and elastic modulus of the PETG models increased with the increase of infill thickness, infill flow rate, and infill overlap length. The results of Taguchi`s test showed that the influence of infill parameters on the tensile properties of PETG models was as follows: infill thickness ] infill flow rate ] infill overlap length; the optimized infill parameters were: infill thickness of 1.2 mm, infill flow rate of 120%, and infill overlap length of 2.8 mm, and the tensile strength of the 3D printed PETG models with optimized parameters was 20.13 MPa, and elastic modulus was 1.32 GPa, which gave the best tensile properties.

Plastics have light weight and excellent performance, which are widely used in all kinds of automobiles. Polypropylene (PP) and its reinforcing materials are used in automotive components, where the surfaces of bumpers and fenders are coated with paint. Traditional recycling can frequently generate various pollutants, such as paint sludge. Microwave pyrolysis is a more environmentally friendly pyrolysis method with a higher heating coefficient than traditional electric pyrolysis. This study first explores the elemental composition of two types of automotive PP plastics and uses thermo-gravimetric analysis and the Kissinger-Akahira-Sunose method to preliminarily calculate the activation energy of automotive PP. The calculation results show that the activation energy of PP containing paint ranges from 189.145 kJ/mol- 199.513 kJ/mol, with an average value of 193.903 kJ/mol. The activation energy of PP without paint is between 215.506 kJ/mol-265.794 kJ/mol, with an average value of 242.425kJ/mol. Then, pyrolysis experiments on PP for vehicles without paint are conducted using a microwave atmosphere tube furnace at different temperatures and microwave powers. The experimental results showed that, when the pyrolysis temperature increased from 500oC to 620 oC, the total proportion of gas products rose from 0.75 wt.% to 4.81 wt.%, and the content of alkanes in the liquid products improved from 26.21 wt.% to 34.37 wt.%; when the microwave power increased from 900 W to 1100 W, the gas product rose to 20.77 wt.%, and the content of aromatic compounds in the liquid product improved to 17.78 wt.%. In addition, the pyrolysis experiment of automotive PP containing paint showed that paint had a relatively minor effect on the pyrolysis products of automotive PP. This study shows that using microwave pyrolysis to treat automotive PP and PP with paint is feasible, which provides a reference for the clean treatment of automotive polymers.

Carbon fiber-reinforced polymer composites are widely used materials in the aircraft industry, automotive sector, marine applications, civil engineering, and daily consumer goods, due to their superior mechanical properties at a relatively low density compared to metallic materials. The studied composites are composed of an epoxy resin matrix in which three layers of carbon fiber fabric are embedded, oriented at 0 and 90 degrees. Carbon fiber-reinforced polymer composites were manufactured using the Vacuum Assisted Resin Transfer Molding technique. The tensile failure mechanism in carbon fiber-reinforced polymer composites is an extremely complex phenomenon influenced by numerous factors. This study aims to evaluate the mechanical behavior of carbon fiber-reinforced composites through tensile testing and to compare experimentally obtained results with those calculated using the mixture rule. Additionally, the behavior of the materials under tensile stress was analyzed using the digital image correlation method. Estimating mechanical properties based on the mixture rule is a common practice in the design phase of polymer composites. This study`s novelty and originality lie in its anticipation of the tensile strength and modulus of elasticity of the studied composites. This anticipation was achieved using a virtual instrument developed in the LabVIEW graphical programming environment. The experimentally obtained results for the tensile characteristics of the studied materials are suitable for this type of composite. These results were compared with estimates derived from the mixture rule, and the absolute error was determined.

Acrylonitrile-butadiene-styrene (ABS) material is widely used as a protective rigid shell and impact absorber in bike helmets, providing vital protection against head injuries under specific working conditions. However, ABS aging in helmets could affect the safety factor of helmets and shorten the service life. Exploring the transformation during aging process for real assembled helmets made of ABS out shells is crucial for the investigation and fabrication of high performance helmets. Herein, the effect of long-term aging on the physical properties of practical helmets made of ABS outer shells has been discussed systematically. Four different types of helmets were subjected to different aging conditions, i.e., outdoor environment, ultraviolet exposure, hot air, and humid-heat conditions. The impact property and stiffness tests were carried out as a function of aging time and aging conditions. The measured helmets were capable of meeting engineering tolerances when aged under outdoor, ultraviolet, and hot air conditions, and could deliver competitive mechanical performance to their pristine helmets. Yet, after aging under humid-heat for 800 h, the helmets showed an obvious decrease in impact strength, gloss, and stiffness. The influence of different aging conditions was further investigated by thermal and spectral characterizations. The study might provide some valuable advice for helmet performance evaluation.