Search Results (29)

In today’s aviation industry, research and studies are carried out to manufacture and design lightweight, high-performance materials. One of the materials developed in line with this goal is glass laminate aluminum-reinforced epoxy (GLARE), which consists of thin aluminum sheets and S2-glass/epoxy layers. Because of its high impact resistance and excellent fatigue and damage tolerance properties, GLARE is used in different aircraft parts, such as the wing, fuselage, empennage skins, and cargo floors. In this study, a survey was carried out and a low-velocity impact model for GLARE materials was developed using the ABAQUS (2014) version V6.14 software and compared with the results of low-velocity impact tests performed according to the American Society for Testing and Materials (ASTM) D7136 standard. This article introduces a novel integrated approach that combines detailed numerical modeling with experimental validation of GLARE 4A FMLs under low-velocity impact. Leveraging ABAQUS, a robust FEM featuring explicit analysis, cohesive resin interfaces, and custom VUMAT subroutines was developed to accurately simulate energy absorption, dent depth, and delamination. The precise model’s predictions align well with test results performed according to ASTM D7136 standards, exhibiting less than a 0.1% deviation in the displacement (dent depth)–time response, along with deviations of 4.3% in impact energy–time and 5.2% in velocity–time trends at 5.5 ms. Full article

The rapid development of 3D printing technology has enabled its application in many fields, including dentistry. One of the key applications is temporary prosthetic restorations on dental implants, used during the osteointegration process. These restorations provide functionality and aesthetics, but their durability under oral conditions exposed to dynamic loads remains a challenge. This pilot study evaluated the thermal expansion and fatigue resistance of three commercially available photopolymer materials used in 3D printing: NextDent Denture 3D, NextDent C&B MFH Bleach, and Graphy TC-80DP. Thermal expansion and dimensional stability analyses were performed on samples subjected to cyclic heating and cooling. Fatigue tests were designed to evaluate the behaviour of the materials under repetitive mechanical loads mimicking chewing. Microscopic analyses (SEM) made it possible to identify the internal structure of the materials and their damage mechanisms. The results showed that the tested materials have a low coefficient of thermal expansion and high dimensional stability after cyclic heating and cooling. However, significant differences were observed in their mechanical properties and fatigue resistance. The best results were obtained for the Graphy TC-80DP material, while NextDent Denture 3D showed the least resistance to cyclic loading. NextDent Denture 3D exhibited the highest thermal expansion coefficient (123.6 × 10⁻⁶/K), while Graphy TC-80DP showed the lowest (83.9 × 10⁻⁶/K), ensuring better dimensional stability. Fatigue tests revealed that Graphy TC-80DP withstood up to 675,221 cycles at 51 MPa, while NextDent Denture 3D failed after 420 cycles. SEM analysis confirmed that Graphy TC-80DP maintained structural integrity longer, while NextDent Denture 3D exhibited early crack propagation. This study fills a gap in the knowledge of the behaviour of dental materials produced with 3D printing technology under real-world conditions and provides a basis for further, more advanced research to improve their properties and patient comfort. Full article

This study evaluated the effect of oral cavity environmental factors on the friction and wear of materials used in 3D-printed orthodontic devices. Commercial materials GR-10 (Pro3Dure) and NextDent SG (NextDent) were examined, with samples produced using ASIGA UV MAX and Phrozen Shuffle Lite 3D printers. Our tests included measurements of hardness, stiffness, elastic modulus, cyclic loading, scratch resistance, and tribological assessments in oscillatory motion. Surface analyses were conducted using scanning electron microscopy with an energy-dispersive spectroscopy analyzer. The results showed that NextDent SG exhibited higher hardness and modulus of elasticity, while GR-10 demonstrated better scratch resistance. Despite similar friction coefficients, significant variations in wear were observed under different environmental conditions, highlighting the importance of considering these factors in the performance of orthodontic materials. Full article

The effect of dispersing multiwalled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) in the matrix on the low-velocity impact resistance and post-impact residual tensile strength of the carbon fiber reinforced epoxy composite laminates has been experimentally analyzed in this study. The composite specimens with the matrix reinforced by different nanoparticle types and various nanoparticle concentrations (0.1, 0.3, and 0.5 wt.%) were prepared and impacted. The post-impact tensile quasi-static and fatigue tests were performed on the specimens with different configurations to study the influence of aforementioned factors on the impact resistance and damage tolerance. Experimental results show that adding nanoparticles in the matrix increases the maximum impact force, reduces the damage area, and alleviates the dent depth of the laminates remarkedly. Moreover, the improvement in these impact resistances increases with the applied nanoparticle concentrations. The nano-modified composite laminates present higher post-impact static strength and longer fatigue life than the specimens with a neat epoxy matrix. Furthermore, both the post-impact static tensile strength and fatigue life increase with the applied nanoparticle concentrations. The damage areas measured using infrared thermography were found to increase linearly with the applied fatigue cycles for all the studied specimens with various configurations. The damage area growth rates of nano-modified composite laminates decrease significantly as the applied nanoparticle concentrations increase. The MWCNTs present better performance than GNPs in improving post-impact static strength and extending the residual fatigue life, however the effect of applied nanoparticle type on the fatigue damage growth rate is slight. Full article

The integration of three-dimensional (3D) printed resin denture teeth represents a significant advancement in digital dentistry. This study aims to assess the ability of 3D-printed denture teeth to withstand chipping and indirect tensile fractures, comparing them with conventionally manufactured resin denture teeth. Four groups, each comprising 30 specimens, were examined: Group 1 featured 3D-printed denture teeth (NextDent, 3D Systems, Soesterberg, The Netherlands), while the others included commercially obtained Ivostar Shade, SpofaDent Plus, and Major Super Lux teeth. Stereolithography 3D printing was utilized to produce methacrylate-based photopolymerized resin teeth models for Group 1, while the remaining groups were commercially sourced. Chipping and indirect tensile fracture tests were performed at a rate of 0.8 mm/min until material failure, offering valuable insights into the mechanical properties of the tested denture teeth. Statistical analysis was carried out using one-way analysis of variance (ANOVA), coupled with Tukey’s honestly significant difference test to compare multiple groups, with a significance threshold of p < 0.05. The findings showed that 3D-printed resin denture teeth exhibited greater indirect tensile fracture resistance than Major Super Lux and Ivostar Shade, though they were surpassed by SpofaDent Plus. In the chipping test, the 3D-printed teeth experienced buccal chipping without distortion, indicating their structural stability under localized force. Fractures during the indirect tensile test originated near the loading point and extended cervically along the inner slopes of both cusps, displaying consistent fracture patterns. These results demonstrate that 3D-printed denture teeth made from resin materials provide adequate fracture resistance for clinical use, although further refinement of materials could enhance their performance relative to conventional alternatives. Full article

This study investigates the blast-resistant performance of a polyurea-coated suspension bridge girder under explosive loads. The Hunan Road Bridge of Shandong was used as a case study through combined test and numerical simulation methods. Two 3 kg TNT charges and one 5 kg TNT charge were used to conduct two single-blast tests and one repeated blast test on a 1:3 scaled segment of a box girder. The tests were labeled as G (box girder without polyurea), PCG (first blast on box girder coated with polyurea), and PCGR (second blast on box girder coated with polyurea). A 1.5 mm polyurea layer was uniformly applied to the top surface. Numerical simulations of the explosion response were performed and validated using LS-DYNA software. The results indicate that under 3 kg of TNT detonation directly above the top plate, sample G exhibited an elliptical perforation, whereas sample PCG only experienced minor local dents without penetration. After a second detonation of 5 kg of TNT above the box chambers, sample PCGR displayed a nearly circular perforation in the top plate, along with cracks near the supports of chambers 1 and 3. For the main girder of the suspension bridge, multiple detonation points caused severe damage, rendering it impassable. However, after polyurea coating, the blast resistance significantly improved, with only minor spalling of concrete on the top plate and no other notable damage, allowing for continued passage. The polyurea layer effectively reduced the vertical displacement of the girder, and this reduction plateaued with increasing coating thickness. Under a 500 kg TNT blast, the optimal polyurea thickness to enhance blast resistance was determined to be 9 mm. Full article

In this study, five three-dimensional angle-interlock fabrics with different warp and weft densities were fabricated using 1000D Kevlar filaments. The Kevlar/EP composites were prepared by vacuum-assisted molding techniques. The low-velocity impact property of the composite was tested, focusing on the effects of the warp and weft densities, impact energy, impactor shape, and impactor diameter. The damage area, dent depth, and crack lengths in the warp and weft direction were used to evaluate the impact performance, and the specimens were compared with plain-weave composites with similar areal densities. The dominant failure mode of the conical impactor was fiber fracture, while the dominant failure mode of the hemispherical impactor was fiber–resin debonding. The cylindrical impactor showed only minor resin fragmentation. The residual flexural strength of the composite after impact was tested to provide insights into its mechanical properties. The study findings will provide a theoretical basis for the optimization of the design of impact-resistant structures using such materials and facilitate their engineering applications. Full article

The high corrosion resistance of fiber-reinforced polymers (FRPs) and related concrete structures means that they are suitable for application in the marine environment. Therefore, the replacement of steel bars with fiber-reinforced polymer (FRP) bars enhances corrosion resistance in seawater sea-sand concrete (SSC) structures. Geometric parameters significantly influence the performance of the bond between ribbed FRP bars and SSC, thereby affecting the mechanical properties of the concrete structures. In this study, the performance of the bond between ribbed (i.e., with fiber wrapping) basalt-fiber-reinforced polymer (BFRP) bars and SSC was investigated through pull-out tests that considered rib geometry and SSC strength. The results demonstrated that an increase in rib and dent widths reduced the bond stiffness, while an increase in rib height and SSC strength gradually increased the bond stiffness and strength. Additionally, the bond stiffness and bond strength were relatively low because the surface fiber bundles buffered the mechanical interlocking force between the BFRP ribs and the concrete, resulting in plastic bond failure during the loading process. Furthermore, the adhesion of the fiber bundles to the surface of the BFRP bars also influenced bond performance, with higher adhesion leading to greater bond stiffness and strength. Full article

Ultra-high Temperature Oxidation-Resistant Alloys (UTORAs) have received a lot of attention due to the increased research demand for deep space exploration around the world. However, UTORAs have the disadvantages of easy oxidation and chalking. So, in this study, a UTORAs is prepared by hot-press sintering on VZrHfNbTa (HEA: High Entropy Alloys can generally be defined as more than five elements by the equal atomic ratio or close to the equal atomic ratio alloying, the mixing entropy is higher than the melting entropy of the alloy, generally forming a high entropy solid solution phase of a class of alloys.) a substrate coated with hafnium. The bonding mechanism, resistance to high-temperature oxidation, and hardness of the sample tests are carried out. The results show that zirconium in the matrix will diffuse into the hafnium coating during the high-temperature sintering process and form the HfZr alloy transition layer, the coating thickness of the composite is about 120 μm, and the diffusion distance of zirconium in the hafnium coating is about 60 μm, this transition layer chemically combines the hafnium coating and the HEA substrate into a monolithic alloy composite. The results of high-temperature oxidation experiments show that the oxidation degree of the hafnium-coated VZrHfNbTa composite material is significantly lower than that of the VZrHfNbTa HEA after oxidation in air at 1600 °C for 5 h. The weight gain of the coated sample after oxidation is 56.56 mg/cm², which is only 57.7% compared to the weight gain of the uncoated sample (98.09 mg/cm² for uncoated), and the surface of the uncoated HEA shows obvious dents, oxidation, and pulverization occurred on the surface and interior of the sample. In contrast, the coated composite alloy sample mainly undergoes surface oxidation sintering to form a dense HfO₂ protective layer, and the internal oxidation of the hafnium-coated VZrHfNbTa composite alloy is significantly lower than that of the uncoated VZrHfNbTa HEA. Full article

In temperate world-wide regions, maize kernels are often infected with the fumonisin-producing fungus Fusarium verticillioides which poses food and feed threats to animals and humans. As maize breeding has been revealed as one of the main tools with which to reduce kernel contamination with fumonisins, a pedigree selection program for increased resistance to Fusarium ear rot (FER), a trait highly correlated with kernel fumonisin content, was initiated in 2014 with the aim of obtaining inbred lines (named EPFUM) with resistance to kernel contamination with fumonisins and adapted to our environmental conditions. The new released EPFUM inbreds, their parental inbreds, hybrids involving crosses of one or two EPFUM inbreds, as well as commercial hybrids were evaluated in the current study. The objectives were (i) to assess if inbreds released by that breeding program were significantly more resistant than their parental inbreds and (ii) to examine if hybrids derived from EPFUM inbreds could be competitive based on grain yield and resistance to FER and fumonisin contamination. Second-cycle inbreds obtained through this pedigree selection program did not significantly improve the levels of resistance to fumonisin contamination of their parental inbreds; however, most EPFUM hybrids showed significantly better resistance to FER and fumonisin contamination than commercial hybrids did. Although European flint materials seem to be the most promising reservoirs of alleles with favorable additive and/or dominance effects for resistance to kernel contamination with fumonisins, marketable new Reid × Lancaster hybrids have been detected as they combine high resistance and yields comparable to those exhibited by commercial hybrids. Moreover, the white kernel hybrid EPFUM-4 × EP116 exploits the genetic variability within the European flint germplasm and can be an alternative to dent hybrid cultivation because white flint grain can lead to higher market prices. Full article

The fracture resistance of 3-unit interim fixed dental prostheses (IFDPs) fabricated using digital light processing (DLP) additive technology with different printing parameters is neglected. Therefore, this study investigates the effect of different printing orientations and different post-curing times on the fracture resistance of 3-unit IFDPs fabricated from two three-dimensional (3D) printed resins, NextDent, C&B (CB), ASIGA, and DentaTOOTH. A 3-unit dye was scanned, and an IFDP was designed. A total of 300 specimens (150/materials, n = 10) were printed and divided into three groups according to printing orientations (0°, 45°, 90°) per material. Each orientation was subdivided into five groups (n = 10) considering the post-curing time (green state as control, 30, 60, 90, and 120 min). All specimens underwent thermocycling (5000 cycles). Each specimen was fitted onto the die and loaded until fracture using a universal testing machine with a loading rate of 1 m/min. Data were analyzed using ANOVA and post hoc Tukey test (α = 0.05). The result showed that printing orientation had a significant effect on the fracture load for both ASIGA and NextDent materials (p < 0.05). The highest fracture load was recorded with 45° orientation, followed by 0° orientation and 90° orientation showed the lowest values per respective post-curing time. Post-curing time increased the fracture load (p < 0.05). Post-curing time had a positive effect on the fracture load. As the post-curing time increased, the fracture resistance load increased (p < 0.05), with 90 and 120 min showing the highest fracture load. The 0° and 45° printing orientations have a high fracture load for 3D-printed IFDPs, and an increased post-curing time is recommended. Full article

We investigated the antimicrobial activity and membrane disruption modes of the antimicrobial peptide mastoparan-AF against hemolytic Escherichia coli O157:H7. Based on the physicochemical properties, mastoparan-AF may potentially adopt a 3–11 amphipathic helix-type structure, with five to seven nonpolar or hydrophobic amino acid residues forming the hydrophobic face. E. coli O157:H7 and two diarrheagenic E. coli veterinary clinical isolates, which are highly resistant to multiple antibiotics, are sensitive to mastoparan-AF, with minimum inhibitory and bactericidal concentrations (MIC and MBC) ranging from 16 to 32 μg mL⁻¹ for E. coli O157:H7 and four to eight μg mL⁻¹ for the latter two isolates. Mastoparan-AF treatment, which correlates proportionally with membrane permeabilization of the bacteria, may lead to abnormal dents, large perforations or full opening at apical ends (hollow tubes), vesicle budding, and membrane corrugation and invagination forming irregular pits or pores on E. coli O157:H7 surface. In addition, mRNAs of prepromastoparan-AF and prepromastoparan-B share a 5′-poly(A) leader sequence at the 5′-UTR known for the advantage in cap-independent translation. This is the first report about the 3–11 amphipathic helix structure of mastoparans to facilitate membrane interaction. Mastoparan-AF could potentially be employed to combat multiple antibiotic-resistant hemolytic E. coli O157:H7 and other pathogenic E. coli. Full article

Durum semolina spaghetti is known to have a low-moderate glycaemic index but the impact of various processing variables during the manufacture and cooking of pasta does affect pasta structure and potentially could alter starch digestion. In this study, several process variables were investigated to see if they can impact the in vitro starch digestion in spaghetti while also monitoring the pasta’s technological quality. Cooking time had a large impact on pasta starch digestion and reducing cooking from fully cooked to al dente and using pasta of very high protein content (17%), reduced starch digestion extent. The semolina particle size distribution used to prepare pasta impacted pasta quality and starch digestion to a small extent indicating a finer semolina particle size (<180 µm) may promote a more compact structure and help to reduce starch digestion. The addition of a structural enzyme, Transglutaminase in the pasta formulae improved overcooking tolerance in low protein pasta comparable to high protein pasta with no other significant effects and had no effect on starch digestion over a wide protein range (8.6–17%). While cold storage of cooked pasta was expected to increase retrograded starch, the increase in resistant starch was minor (37%) with no consequent improvement in the extent of starch digestion. Varying three extrusion parameters (die temperature, die pressure, extrusion speed) impacted pasta technological quality but not the extent of starch digestion. Results suggest the potential to subtly manipulate the starch digestion of pasta through some processing procedures. Full article

Nowadays, agriculture is under the pressure of climate change and new pathogen outbreaks while farmers are requiring breeders to develop more resistant and resilient genotypes. The genetic base for breeding may be increased through appropriate conservation, description and characterization of local varieties and germplasm collections that have never been used in breeding, and which could be sources of useful alleles. In this framework, the present paper focuses on eight maize landraces of the eastern part of Emilia-Romagna, derived from the Italian maize collection sampled in 1954. Landraces are characterized by a short cycle length and different kernel types—mainly flint-like or an intermediate type of yellow or yellow–orange color—while dent landraces are less represented. Pigmented and white corns are absent even though one landrace (Va213) showed the presence of scattered blue kernels on yellow ears. Ear shape is frequently conical, a trait associated with drought-resistance and common in Italian traditional landraces. Genetic characterization was carried out on 529 individuals by using 10 SSR markers. A total of 68 different alleles, ranging from 4 for markers (phi084 and umc1401) to 11 (phi031) and from 27 (Va217) to 50 (Va211), were evidenced at the individual and population level. AMOVA analysis revealed a small amount (19%) of variability between populations, as supported also by PCoA, with the only exception of Va217, which is different from the others, as evidenced also by phylogenetic analysis. Population structure analysis resulted in the identification of three and four population levels, which are consistent with previous results. Full article

This study evaluated the fracture resistance, biaxial flexural strength (BFS), and dynamic mechanical analysis (DMA) of three-dimensional (3D) printing resins for the esthetic restoration of primary molars. Two 3D printing resins, Graphy (GP) and NextDent (NXT), and a prefabricated zirconia crown, NuSmile (NS), were tested. GP and NXT samples were 3D printed using the workflow recommended by each manufacturer. Data were collected and statistically analyzed. As a result of the fracture resistance test of 0.7-mm-thick 3D printed resin crowns with a thickness similar to that of the NS crown, there was no statistically significant difference among GP (1491.6 ± 394.6 N), NXT (1634.4 ± 289.3 N), and NS (1622.8 ± 323.9 N). The BFS of GP was higher for all thicknesses than that of NXT. Both resins showed high survival probabilities (more than 90%) when subjected to 50 and 150 MPa. Through DMA, the glass transition temperatures of GP and NXT were above 120 °C and the rheological behavior of GP and NXT according to temperature and frequency were analyzed. In conclusion, GP and NXT showed optimum strength to withstand bite forces in children, and 3D printed resin crowns could be an acceptable option for fixed prostheses of primary teeth. Full article