Search Results (23)

Bell towers, due to their slender geometry and structural configuration, are among the buildings most susceptible to deterioration from weathering and seismic events. These aspects influence the structural assessment of these historic towers, which is essential for their conservation and maintenance. The “Carmine Maggiore” bell tower in Naples (Italy) has been an important and prominent landmark of the city for centuries. It is square in plan and 72 m high. Over time, it suffered extensive damage and was severely damaged by the earthquake of 1456. Reconstruction began in the first decade of the 17th century and the original design was modified, adding two stories and changing the shape of the plan to octagonal. In the centuries that followed, the structure was damaged again and further interventions were carried out, adding tie-rods and replacing damaged elements. Today, the bell tower has very elaborate façades with mouldings and decorations, so that the supporting structure appears to be covered with plaster, stucco, and stone elements. This paper describes the results of FEM analyses of the bell tower, obtained from models with different levels of complexity to evaluate the influence of stone cladding elements on the seismic behaviour. In particular, the difference in the IS safety indices, calculated as the ratio of capacity to demand, exceeds 15%, due to the mechanical consistency of the cladding elements, which contribute significantly to both stiffness and strength. Full article

Additive manufacturing (AM) has swiftly emerged as a substitute for conventional methods such as machining and injection moulding. Its appeal is attributed to accelerated prototyping, improved sustainability, and the capacity to fabricate intricate shapes. Nonetheless, the size constraints of additive manufacturing components require the assembly of smaller 3D-printed elements to create larger structures. This study investigates the tensile properties of scarf joints (SJs) created from several polymers, including ABS, PETG, and PLA, adhered with Araldite^® 2015 and Sikaforce^® 7752 adhesives. The characteristics of the adherends were assessed prior to examining the adhesive efficacy in the SJ configuration. Experimental evaluations quantified failure modes, joint strength, assembly stiffness, and energy at failure, comparing findings with predictions from a cohesive zone model (CZM). The objective was to determine the ideal combination of materials and adhesives for enhanced joint performance. Results indicated that joint performance is greatly affected by the adherend material, adhesive selection, and scarf angle. PLA and Araldite^® 2015 typically exhibited optimal strength and stiffness, but Sikaforce^® 7752 demonstrated enhanced energy absorption for extended bonding lengths. Full article

Moulds for aeronautical applications must fulfil highly demanding requirements, including the geometrical tolerances before and after curing cycles at high temperatures and pressures. The growing availability of thermoplastic materials printed by material extrusion systems requires research to verify the geometrical accuracy after three-dimensional printing processes to assess whether the part can meet the required geometry through milling processes. In this sense, the application of automated techniques to assess quick and reliable measurements is an open point under this promising technology. This work investigates the integration of a 3D vision system using a structured-light 3D scanner, placed onto an industrial robot in an eye-in-hand configuration and synchronized by a computer. The complete system validates an in-house algorithm, which inspects the whole reconstructed part, acquiring several views from different poses, and makes the alignment with the theoretical model of the geometry of big parts manufactured by 3D printing. Moreover, the automation of the validation process for the manufactured parts using contactless detection of the offset-printed material can be used to define milling strategies to achieve the geometric qualifications. The algorithm was tested using several parts printed by the material extrusion of a thermoplastic material based on black polyamide 6 reinforced with short carbon fibres. The complete inspection process was performed in 38 s in the three studied cases. The results assure that more than 95.50% of the evaluated points of each reconstructed point cloud differed by more than one millimetre from the theoretical model. Full article

Two-component micro-powder injection moulding (2C-μPIM) is a prospective approach for fabricating bi-material micro-components of stainless steel 316L (SS316L) and 3 mol% yttria-stabilised zirconia (3YSZ) at an appealing cost. However, the fundamental challenge lies in preventing the formation of large-scale cracks at the interface of two different materials during sintering. This study investigated how SS316L nanoparticles in bimodally configured SS316L powder that incorporated both nanoparticles and microparticles influenced the sintering of 2C-μPIM-processed miniature bi-materials made of bimodal SS316L and 3YSZ. In this study, feedstocks were developed by integrating monomodal (micro-sized) SS316L powder, three types of nano/micro-bimodal SS316L powders, and 3YSZ powder individually with palm stearin and low-density polyethylene binders. The results indicated that increasing the SS316L nanoparticle content to 45 vol.% caused a 19.5% increase in the critical powder loading in the bimodal SS316L powder as compared to that in the monomodal SS316L powder. The addition of SS316L nanoparticles increased the relative density and hardness of the sintered bi-materials, with the maximum values obtained being 96.8% and 1156.8 HV, respectively. Field emission scanning electron microscopy investigations revealed that adding 15 vol.% and 30 vol.% SS316L nanoparticle contents reduced interface cracks in bi-materials significantly, while 45 vol.% resulted in a crack-free interface. Full article

This article presents the results of testing the suitability of X-ray computed tomography for the quality control of the casting moulds used for producing turbine blades. The research was focused on the analysis of cross-sectional images, spatial models and the porosity of moulds using a Phoenix L 450 microtomograph. The research material consisted of samples from three mixtures of ceramic materials and binders intended for producing casting moulds using the lost wax method. Various configurations of filling materials (Molochite and quartz flours) and binder (Remasol, Ludox PX 30 and hydrolysed ethyl silicate) mixtures were considered. X-ray computed tomography enabled the detection of a number of defects in the ceramic mass related to the distribution of mass components, porosity concentration and defects resulting from the specificity of the mould production. It was found that casting mould quality control on cross-sectional tomographic images is faster and as accurate as the analysis of three-dimensional models and allows for the detection of a whole range of ceramic defects, but the usefulness of the images is greatest only when the cross-sections are taken at an appropriate angle relative to the object being examined. Full article

The fabrication of bi-material micro-components via two-component micro-powder injection moulding (2C-µPIM) from 3 mol% yttria-stabilised zirconia (3YSZ) and micro/nano bimodal stainless steel 316L (SS 316L) powders has received insufficient attention. Apart from this, retaining the bonding between ceramic and metal at different processing stages of 2C-µPIM is challenging. This study investigated the solvent and thermal debinding mechanisms of green bi-material micro-parts of 3YSZ and bimodal SS 316L without collapsing the ceramic/metal joining. In this research, feedstocks were prepared by integrating the powders individually with palm stearin and low-density polyethylene binders. The results demonstrated that during the solvent debinding process, the palm stearin removal rate in the bi-materials composed of 3YSZ and bimodally configured SS 316L feedstocks intensified with an increase in temperature. The establishment of interconnected pores in the solvent-debound components facilitated the thermal debinding process, which removed 99% of the binder system. Following sintering, the debound bi-materials exhibited a relative density of 95.3%. According to a study of the microstructures using field emission scanning electron microscopy, an adequate bond between 3YSZ and bimodal SS 316L was established in the micro-part after sintering. The bi-material sintered at 1350 °C had the highest hardness of 1017.4 HV along the joining region. Full article

This paper discusses the design and integration of an elastic sensor sheet for SENSOMATT, a smart device that predicts pressure ulcers caused by prolonged skin pressure. It covers the mechanical and electrical aspects of the sensor sheet design, including material selection, mould and tooling design, and network design. The paper describes testing of different configurations of the sensor sheet and various network structures. The final design of the sensor sheet is successfully constructed and tested, and the article provides a brief introduction to the printed circuit board design and manufacturing process. Full article

Natural fibre–polymer composites are widely used because they are economical and ecologically beneficial in a variety of applications. In order to improve its performance, this study focuses on examining the mechanical characteristics of an epoxy composite material that has been reinforced with banana fibre mats that have undergone NaOH treatment. Additionally, using various configurations both with and without eggshell powder (ESP), the compression moulding method was used to fabricate and investigate the impact of ESP on these mechanical qualities. The results showed that the composite with 25 weight percent banana fibre and 2.5 weight percent ESP had the maximum tensile strength (31.21 MPa), bending strength (33.69 MPa), and impact strength (2.84 kJ/m²). Strong interfacial adhesion between the banana and eggshell components was discovered via the microscopic examination of shattered surfaces. Notably, compared to untreated banana composites, the alkaline-treated banana materials showed fewer occurrences of pull-outs and fractures, leading to noticeably better mechanical performance. Full article

In this work, an attempt was made to improve the mechanical performance of glass fibre-reinforced polymer composites by adding multi-walled carbon nanotubes (MWCNT) and graphene nanoparticles (GNP) and their hybrid combination at different weight fractions (0.1 to 0.3%). Composite laminates with three different configurations (unidirectional [0°]₁₂, cross-ply [0°/90°]_3s, and angle-ply [±45°]_3s) were manufactured using the compression moulding method. Characterisation tests such as quasistatic compression, flexural, and interlaminar shear strength properties were carried out per ASTM standards. Failure analysis was carried out through optical and scanning electron microscopy (SEM). The experimental results showed a substantial enhancement with the 0.2% hybrid combination of MWCNTs, and GNPs showed 80% and 74% in the compressive strength and compressive modulus, respectively. Similarly, flexural strength, modulus, and interlaminar shear strength (ILSS) increased by 62%, 205%, and 298%, respectively, compared to neat glass/epoxy resin composite. Beyond the 0.2% of fillers, the properties started to degrade due to the agglomeration of MWCNTs/GNPs. The order of layups per mechanical performance was UD, followed by CP and AP. Full article

As a consequence of climate change, hotels are under mounting pressure to cut their carbon emissions, reduce their waste, and overall become more responsible in their operations. Given this context, experts claim that organisational human resources practices have immense ability to mould the behaviours of individuals. On the basis of w theory, we used a configuration of green human resources management, environmentally specific servant leadership, and psychological green climate to develop causal recipes for stimulating green creativity in hotel employees. Data were collected from 418 employees and analysed using an fsQCA to test the proposed model. Findings revealed that no single construct was sufficient to predict employees’ green creativity, but three causal recipes (i.e., green human respurces management, environmentally specific servant leadership, and psychological green climate) can be demonstrated to produce high green creativity. The study findings show that green human resources managment practices influence individual green creativity. It also indicated that environmentally specific servant leadership is a key driver of green creativity. Moreover, psychological green climate has a signifcant influence on green creativity. Our study has meaningful implications for hotel managers that can help them to develop new approaches and strategies to improve the employees’ green creativity by paying attention to green human resources managment practices, environmentally specific servant leadership, and psychological green climate. Full article

This study looks at how incorporating nanofiller into sisal/flax-fibre-reinforced epoxy-based hybrid composites affects their mechanical and water absorption properties. The green Al₂O₃ NPs are generated from neem leaves in a proportion of leaf extract to an acceptable aluminium nitrate combination. Both natural fibres were treated with different proportions of NaOH to eliminate moisture absorption. The following parameters were chosen as essential to achieving the objectives mentioned above: (i) 0, 5, 10, and 15% natural fibre concentrations; (ii) 0, 2, 4, and 6% aluminium powder concentrations; and (iii) 0, 1, 3, and 5% NaOH concentrations. Compression moulding was used to create the hybrid nanocomposites and ASTM standards were used for mechanical testing such as tension, bending, and impact. The findings reveal that combining sisal/flax fibre composites with nanofiller improved the mechanical features of the nanocomposite. The sisal and flax fibre hybridised successfully, with 10% fibres and 4% aluminium filler. The water absorption of the hybrids rose as the fibre weight % increased, and during the next 60 h, all of the specimens achieved equilibrium. The failed samples were examined using scanning electron Microscopic (SEM) images better to understand the composite’s failure in the mechanical experimentations. Al₂O₃ NPs were confirmed through XRD, UV spectroscope and HPLC analysis. According to the HPLC results, the leaf’s overall concentrations of flavonoids (gallocatechin, carnosic acid, and camellia) are determined to be 0.250 mg/g, 0.264 mg/g, and 0.552 mg/g, respectively. The catechin concentration is higher than the phenolic and caffeic acid levels, which could have resulted in a faster rate of reduction among many of the varying configurations, 4 wt.% nano Al₂O₃ particle, 10 wt.% flax and sisal fibres, as well as 4 h of NaOH with a 5 wt.% concentration, producing the maximum mechanical properties (59.94 MPa tension, 149.52 Mpa bending, and 37.9 KJ/m² impact resistance). According to the results, it can be concluded that botanical nutrients may be used effectively in the manufacturing of nanomaterials, which might be used in various therapeutic and nanoscale applications. Full article

Discontinuous fibre reinforced composites enable the manufacture of integrated structural components via the complex flow process of compression moulding. However, such processes can lead to the formation of detrimental weld-lines. Here, the meso-structure of carbon fibre sheet moulding compounds (C-SMC) was analysed using conventional non-destructive techniques and automated eddy current (EC) scanning, as well as destructive methods, in an attempt to identify defects such as weld-lines in this class of materials. Compression-moulded plaques with forced weld-lines in two different configurations (adjacent and opposing flow joints) were analysed, showing up to 80% strength reduction versus a defect-free plaque. The EC-determined local fibre orientation and elucidated local microstructure matched those obtained using conventional techniques, showing a dramatic fibre tow alignment parallel to the weld-lines. It was found that failure occurred in proximity to the “non-uniformity” defect regions identified by EC analyses, demonstrating the use of robot-guided EC for successful defect detection in C-SMC structures. Full article

The machining of free-formed surfaces, e.g., dies or moulds, is often affected by tool vibrations, which can affect the quality of the workpiece surface. Furthermore, in 5-axis milling, the dynamic properties of the system consisting of the tool, spindle and machine tool can vary depending on the tool pose. In this paper, a simulation-based methodology for optimising the tool orientation, i.e., tilt and lead angle of simultaneous 5-axis milling processes, is presented. For this purpose, a path finding algorithm was used to identify process configurations, that minimise tool vibrations based on pre-calculated simulation results, which were organised using graph theory. In addition, the acceleration behaviour of the feed drives, which limits the ability of adjusting the tool orientation with a high adaption frequency, as well as potential collisions of the tool, tool chuck and spindle with the workpiece were considered during the optimisation procedure. Full article

In this study, Polyurea/Formaldehyde (PUF) microcapsules containing Dicyclopentadiene (DCPD) as a healing substance were fabricated in situ and mixed at relatively low concentrations (<2 wt%) with a thermosetting polyurethane (PU) foam used in turn as the core of a sandwich structure. The shape memory (SM) effect depended on the combination of the behavior of the PU foam core and the shape memory polymer composite (SMPC) laminate skins. SMPC laminates were manufactured by moulding commercial carbon fiber-reinforced (CFR) prepregs with a SM polymer interlayer. At first, PU foam samples, with and without microcapsules, were mechanically tested. After, PU foam was inserted into the SMPC sandwich structure. Damage tests were carried out by compression and bending to deform and break the PU foam cells, and then assess the structure self-healing (SH) and recovery capabilities. Both SM and SH responses were rapid and thermally activated (120 °C). The CFR-SMPC skins and the PU foam core enable the sandwich to exhibit excellent SM properties with a shape recovery ratio up to 99% (initial configuration recovery). Moreover, the integration of microcapsules (0.5 wt%) enables SH functionality with a structural restoration up to 98%. This simple process makes this sandwich structure ideal for different industrial applications. Full article

Material extrusion based additive manufacturing is used to make three dimensional parts by means of layer-upon-layer deposition. There is a growing variety of polymers that can be processed with material extrusion. Thermoplastic polyurethanes allow manufacturing flexible parts that can be used in soft robotics, wearables and flexible electronics applications. Moreover, these flexible materials also present a certain degree of viscoelasticity. One of the main drawbacks of material extrusion is that decisions related to specific manufacturing configurations, such as the inner-structure design, shall affect the final mechanical behaviour of the flexible part. In this study, the influence of inner-structure design factors upon the viscoelastic relaxation modulus, E(t), of polyurethane parts is firstly analysed. The obtained results indicate that wall thickness has a higher influence upon E(t) than other inner-design factors. Moreover, an inadequate combination of those factors could reduce E(t) to a small fraction of that expected for an equivalent moulded part. Next, a viscoelastic material model is proposed and implemented using finite element modelling. This model is based on a generalized Maxwell model and contemplates the inner-structure design. The results show the viability of this approach to model the mechanical behaviour of parts manufactured with material extrusion additive manufacturing. Full article