Mechanical Properties Of Materials Research Articles

Encapsulation of Bacillus subtilis in Electrospun Poly(3-hydroxybutyrate) Fibers Coated with Cellulose Derivatives for Sustainable Agricultural Applications.

One of the latest trends in sustainable agriculture is the use of beneficial microorganisms to stimulate plant growth and biologically control phytopathogens. Bacillus subtilis, a Gram-positive soil bacterium, is recognized for its valuable properties in various biotechnological and agricultural applications. This study presents, for the first time, the successful encapsulation of B. subtilis within electrospun poly(3-hydroxybutyrate) (PHB) fibers, which are dip-coated with cellulose derivatives. In that way, the obtained fibrous biohybrid materials actively ensure the viability of the encapsulated biocontrol agent during storage and promote its normal growth when exposed to moisture. Aqueous solutions of the cellulose derivatives-sodium carboxymethyl cellulose and 2-hydroxyethyl cellulose, were used to dip-coat the electrospun PHB fibers. The study examined the effects of the type and molecular weight of these cellulose derivatives on film formation, mechanical properties, bacterial encapsulation, and growth. Scanning electron microscopy (SEM) was utilized to observe the morphology of the biohybrid materials and the encapsulated B. subtilis. Additionally, ATR-FTIR spectroscopy confirmed the surface chemical composition of the biohybrid materials and verified the successful coating of PHB fibers. Mechanical testing revealed that the coating enhanced the mechanical properties of the fibrous materials and depends on the molecular weight of the used cellulose derivatives. Viability tests demonstrated that the encapsulated B. subtilis exhibited normal growth from the prepared materials. These findings suggest that the developed fibrous biohybrid materials hold significant promise as biocontrol formulations for plant protection and growth promotion in sustainable agriculture.

Experimental research on the glass fiber-reinforced effect and mechanisms of sand powder 3D-printed rock-like materials

Conducting laboratory tests on natural rocks has significant value for the scientific and practical advancement of various types of rock engineering. The investigation of a rock-like materials that is similar in characteristics and structure to natural rock is key to the further advancement of laboratory rock experiments. The rapid development of sand powder 3D printing technology in recent years has provided a solution for fabricating rock-like materials. However, the low strength and elastic modulus of sand powder 3D-printed materials limit their application in simulating natural rocks. Therefore, this paper proposes a method to enhance the mechanical properties of sand powder 3D-printed materials utilizing glass fiber reinforcement by incorporating glass fiber into sand powder 3D-printed rock-like specimens. The mechanical properties and microstructural variations of the specimens with varying glass fiber contents are investigated utilizing mechanical testing, acoustic emission, scanning electron microscopy, etc. The results indicate that (1) it is feasible to utilize glass fiber to enhance the mechanical properties of sand powder 3D-printed materials; (2) The mechanical properties of sand powder 3D printing materials are significantly enhanced by the addition of glass fiber; and (3) the mechanisms controlling the reinforcement effect of glass fiber addition on sand powder 3D-printed specimens are determined by analyzing the microstructural characteristics of the specimens. This study improves the applicability of sand powder 3D-printed materials in simulating natural rock, thereby promoting the further application of 3D printing in the field of rock mechanics.

Combining machine learning and molecular dynamics to predict strength-toughness and energy dissipation mechanisms of hybrid double-crosslinked CNT networks

Cross-linking has a significant strengthening effect on the mechanical properties of carbon nanoparticles, but there are still great challenges in how to control their mechanical properties through precise cross-linking ratios. Therefore, we use coarse-grained molecular dynamics (CGMD) to simulate its mechanical properties as data samples and combine it with machine learning methods to predict the optimal strength and toughness of carbon nanotubes (CNTs) corresponding to optimal cross-linking conditions. We found that the cross-linking density range is 2.60 ∼ 2.75 × 10-4/nm3, and the strong and weak cross-linking ratio range is 91 % S+9% W∼95 % S+5% W, which is the optimal range to achieve the mechanical properties of CNTs. Excessively high cross-link density and strong bond ratios can reduce the total number of cross-link bond breaks, thus decreasing their toughness. Meanwhile, high cross-linking density has a greater impact on the shear and slip between CNTs, tending to make CNTs brittle. Our proposed new approach for extracting data from coarse-grained models can obtain substantial optimization results without requiring much simulation computation. Furthermore, these cross-linking strategies and machine learning algorithms proposed in this work can provide a theoretical basis for controlling the mechanical properties of CNT materials, and also open up a new way for functional network materials other than CNTs.

Mechanical properties of epoxy composites filled with multi-walled carbon nanotube, Nanoaluminum particles and glass fibers at elevated temperatures

The present work investigates the mechanical properties of a composite material composed of multi-walled carbon nanotubes (MWCNTs), nano-aluminum powder (NAP), and glass fibers (GF) for five different compositions. The study further investigated how MWCNTs contribute to maintaining the mechanical properties of nanocomposites when exposed to elevated temperatures, up to 180 °C. The evaluation of impact strength revealed that the nanocomposite, composed of 2 % MWCNTs, 15 % NAP, and 10 % GF, demonstrated the greatest impact strength. At room temperature, the composite containing 2 % MWCNTs, 5 % NAP, and 20 % GF exhibited the highest ultimate tensile strength (UTS). Conversely, at elevated temperatures reaching up to 180 °C, the highest UTS was observed in the composition with 2 % MWCNTs, 10 % NAP, and 15 % GF. The hardness of the nanocomposite was influenced by its composition; at room temperature, the maximum hardness was observed in the mixture containing 2 % MWCNTs, 20 % NAP, and 5 % GF. In contrast, at elevated temperatures, the composition with 2 % MWCNTs, 5 % NAP, and 20 % GF exhibited the highest hardness. Overall, the study found that incorporating GF and NAP improved the mechanical properties of the composite. These results indicate that the composite's performance could be further optimized for specific applications through the addition of filler materials.

Microstructure evolution in laser powder bed fusion melted 2205 duplex stainless steel using in-situ EBSD during uniaxial tensile testing

Compared to duplex stainless steels (DSSs) prepared by traditional methods, specimens produced through laser powder bed fusion (LPBF) exhibit excellent yield strength but lower elongation. To improve elongation, understanding microstructure evolution during uniaxial tensile testing is crucial. This study investigates the slip behavior, grain boundary evolution, and phase transformation of LPBF 2205 duplex stainless steel during tensile deformation using in-situ electron backscatter diffraction (EBSD). Results show the formation of slip bands, which increase in number as loading stress rises. The primary slip systems activated are {110}<111> in ferrite and {111}<110> in austenite. In the ferrite phase, slip dislocations accumulate and generate low-angle grain boundaries (LAGBs), which evolve into high-angle grain boundaries (HAGBs), refining the grain structure. Numerous Σ3 annealing twins form in the austenite phase, but detwinning and twinning reduce Σ3 content as deformation processes. Ferrite and austenite exhibit good stability during the initial stages of tensile deformation. However, some austenite transforms into martensite through the transformation-induced plasticity (TRIP) effect at the final stages of deformation, which helps relieve stress concentration and delays material fracture. This study provides valuable insights for optimizing microstructure to improve the mechanical properties of LPBF materials.

The relationship between mechanical properties and mineralogical composition of some sedimentary rocks

The physical and mechanical properties of rock material are remarkably associated with the comprising mineralogical composition and textural characteristics. Therefore, meticulous understanding of the role of mineralogical composition in engineering behavior of sedimentary rocks is essential. For this purpose, both matrix and aggregates of rocks must be thoroughly analyzed to obtain a comprehensive insight of this aspect. The main objective of this study is to investigate the extent of complexity of the relationship between mineralogical and mechanical properties of some sedimentary rocks. Several sedimentary rock samples from different regions of Iran were analyzed in this study. The same samples were then tested to determine uniaxial compressive strength, tensile strength, Schmidt hammer hardness, and Cerchar Abrasivity index. The relationship between these properties and the mineralogical composition were described by linear and multivariate regression analyses. The research unequivocally establishes a significant correlation between specific mechanical parameters and mineralogical composition. Moreover, the findings highlight the relative importance of each parameter, with some being more crucial than others.

Research on the Configuration of Multi-Component Solid Waste Cementitious Materials and the Strength Characteristics of Consolidated Aeolian Sand

Developing green, low-carbon building materials has become a viable option for managing bulk industrial solid waste. This paper presents a kind of all solid waste cementitious material (SWCM), which is made entirely from six common industrial wastes, including carbide slag and silica fume, that demonstrate strong mechanical properties and effectively stabilize aeolian sand (AS). Initially, we investigated the mechanical strength of waste-based cementitious materials in various mix ratios, focusing on their ability to stabilize river sand (RS) and aeolian sand. The results show that it is necessary to use alkaline solid waste carbide slag to provide a suitable reaction environment to achieve the desired strength. In contrast, the low reactivity of coal gangue powder did not contribute effectively to the strength of the cementitious material. Further orthogonal experiments determined the impact of different waste dosages on the strength of stabilized AS. It was found that increasing the amounts of carbide slag, silica fume, and blast furnace slag powder improved strength, while increasing fly ash first increased and then decreased strength. In contrast, higher additions of desulfurization gypsum and coal gangue powder led to a continuous decrease in strength. The optimized mix is carbide slag—desulfurization gypsum—fly ash—silica fume—blast furnace slag powder in a ratio of 4:2:2:3:3. The experimental results using SWCM to stabilize AS indicated a proportional relationship between strength and SWCM content. When the content is ≥20%, it meets the strength requirements for road subbases. The primary hydration products of stabilized AS are C-(A)-S-H, AFt, and CaCO3. Increasing the SWCM content enhances the reaction degree of the materials, thereby improving mechanical strength. This study highlights the mechanical properties of cementitious materials made entirely from waste for stabilizing AS. It provides a reference for the large-scale utilization of industrial solid waste and practical applications in desert road construction.

Investigation of structural, electronic, optical, and mechanical properties of perovskite CsPbBr3 material through induced pressure for photovoltaic applications: A DFT Insights

Herein, perovskite CsPbBr3 material was computationally explored at pressure limits from 0.0 to 8.0 GPa using a 5-step (2GPa gap) calculation. CASTEP (Cambridge Serial Total Energy Package) program is used which is based on density functional theory (DFT), with an ultra-soft (US) pseudo-potential (SP) plane wave and the GGA-PBE exchange–correlation functional. When the pressure increases from 0.0 to 8.0 GPa, the bandgap decreases from 1.84 to 0.60 eV. In comparison to higher pressures, the bandgap decreases significantly until 8.0 GPa. The mechanical properties of the compound at various pressures are also investigated, which indicates that the compound is mechanically ductile and stable in nature. Various optical characteristics, such as the refractive index, loss function, absorption coefficient, and reflectivity, have been determined under pressure limits from 0.0 to 8.0 GPa. For solar cell applications, a compound with high absorption, refractive index, and optical conductivity is optimal.

Investigation on the pore size characteristics and mechanical properties of grouting materials scoured by flow water

Investigating the pore size characteristics and mechanical properties of the stone bodies formed by residual grout is crucial for understanding the authentic permeability and load-bearing capacity of grouting materials after being scoured by water flow. In this study, the pore size distribution, porosity, uniaxial compressive strength (UCS), and elastic modulus (E) of stone bodies formed by residual grout from polyacrylate latex-modified cement grouting material (PLMC) were systematically investigated, and pure cement grout (PC) as a control group. First, scouring tests were conducted on grouting materials with various water-to-cement ratios (w/c, 0.6–0.8) and polymer-cement ratios (p/c, 0–0.2) under different flow velocities (0–1 m/s). Subsequently, the pore size characteristics of stone bodies formed by residual grout under various conditions were studied via nuclear magnetic resonance test. Finally, the uniaxial compression tests were conducted to investigate the impact of water scouring on the mechanical properties of grouting materials, and the relationship between pore size characteristics and macro mechanical responses was analyzed. Results show that the stone bodies formed by residual grout compared to the non-scoured state develop mesopores and macropores, and the number of micropores also increased significantly. This porosity escalation results in a reduction in UCS and E. When the flow velocity reaches 1 m/s, the porosity of PLMC with w/c = 0.8 increases by 2.95 %, while UCS decreases by 14.6 % and E decreases by 37.4 %. PC demonstrates more pronounced changes, with a porosity increase of 7.01 %, UCS decreases by 32.9 %, and E decreases by 41.5 %. With the rise in w/c, the deterioration of pore structure and mechanical properties of the stone bodies formed by residual grout is more significant compared to the non-scoured state. Increasing p/c can mitigate the deterioration of the pore structure and mechanical properties. The findings provide meaningful guidance for the grouting reinforcement under dynamic water conditions.

On the Use of a Chloride or Fluoride Salt Fuel System in Advanced Molten Salt Reactors, Part 3; Radiation Damage

Structural materials in fast reactors with harsh radiation environments due to high energy neutrons—compared to thermal reactors—potentially suffer from a higher degree of radiation damage. This radiation damage can change the thermophysical and mechanical properties of materials and, as a result, alter their performance and effective lifetime, in some cases leading to their disintegration. These phenomena can jeopardize the safety of fast reactors and thus need to be investigated. In this study, the effect of radiation damage on the vessels of molten salt fast reactors (MSFR) was evaluated based on two fundamental radiation damage parameters: displacement per atom (dpa) and primary knock-on atom (pka). Following the previous part of this article (Parts 1 and 2), an iMAGINE reactor core design (University of Liverpool, UK—chloride-based salt fuel system) and an EVOL reactor core design (CNRS, Grenoble, France, fluoride-based salt fuel system) with stainless steel and nickel-based alloy material vessels, respectively, were considered as case studies. The SPECTER and SPECTRA-PKA codes and a PTRAC card of MCNPX, integrated with a module which has been developed in MATLAB, named PTRIM and SRIM-2013 (using binary collision approximation), were employed individually to calculate and compare dpa and PKA (this master module containing all three tools has been appended to the iMAGINE-3BIC package for future use during reactor operations). Additionally, SRIM-2013 was applied in a 3D simulation of a radiation damage map on a small sample of vessels based on the calculated PKA. Our results showed a higher degree of radiation damage in the iMAGINE vessel compared to the EVOL one, which could be expected due to the harder neutron flux spectrum of the iMAGINE core compared to EVOL. In addition, the nickel alloy vessel showed better radiation damage resistance against high energy neutrons compared to the stainless steel one, although more investigations are required on thermal neutrons and alloy corrosion mechanisms to determine the best material for use in MSFR vessels.

Preparation, Mechanical and Thermal Insulation Properties of Graphene Oxide/Polydopamine/Polyurethane Foam‐Based Tunnel Insulation Liner Material

This article designs a novel tunnel insulation liner material based on polyurethane foam (PUF), aiming to improve the liner material's mechanical properties, hydrophobicity, thermal insulation properties and to reduce the self‐weight of the material. Firstly, PUF is self‐made using a one‐step method, and the optimal parameter combination is optimized through the single‐parameter (SP) method. Secondly, based on the optimal parameter combination of PUF, a new process is employed to prepare polydopamine (PDA)/graphene oxide (GO)/PUF. Compression experiments and contact angle tests are conducted to assess the physical mechanical properties of PDA/GO/PUF. Infrared thermography and combustion experiments are employed to characterize the thermal insulation performance of PDA/GO/PUF. Microscopic mechanisms are explained through thermogravimetric analysis (TG), scanning electron microscopy (SEM), and Fourier‐transform infrared spectroscopy (FTIR). The results show that: the optimal parameter combination of tin(II) bis(2‐ethylhexanoate) (TEH), water (H2O), and toluene‐2,4‐diisocyanate (TDI) content optimized by the SP method is 4 parts, 2.8 parts, and 19 parts. PUF prepared based on the optimal parameter combination exhibits a dense and uniform cell structure with low density. Under cyclic loading, PDA/GO/PUF composite material exhibits excellent mechanical stability and fatigue resistance; the hydrophobicity, thermal insulation, and thermal stability of PDA/GO/PUF are significantly improved compared to PUF.

Assessing Mechanochemical Properties of Acrylonitrile Butadiene Styrene (ABS) Items in Cultural Heritage Through a Multimodal Spectroscopic Approach.

A multimodal spectroscopic approach is proposed to correlate the mechanical and chemical properties of plastic materials in art and design objects, at both surface and subsurface levels, to obtain information about their conservation state and to monitor their degradation. The approach was used to investigate the photo-oxidation of acrylonitrile butadiene styrene (ABS), a plastic commonly found in many artistic and design applications, using ABS-based LEGO bricks as model samples. The modifications of the chemical and viscoelastic properties of ABS during photoaging were monitored by correlative Brillouin and Raman microspectroscopy (BRaMS), combined with portable and noninvasive broad-range external reflection infrared (IR) spectroscopy and nuclear magnetic resonance (NMR) relaxometry, directly applicable in museums. BRaMS enabled combined measurements of Brillouin light scattering and Raman spectroscopy in a microspectroscopic setup, providing for the coincident probe of the chemical and mechanical changes of ABS at the sample surface. NMR relaxometry allowed for noninvasive measurements of relaxation times and depth profiles which are directly related to the molecular mobility of the material. Complementary chemical information was acquired by external reflection IR spectroscopy. The simultaneous probe of the chemical and mechanical properties by this multimodal spectroscopic approach enabled us to define a decay model of ABS in terms of compositional changes and variation of stiffness and rigidity occurring with photodegradation. The knowledge acquired on LEGO samples has been used to rate the conservation state of ABS design objects noninvasively investigated by external reflection Fourier transform IR spectroscopy and NMR relaxometry offered by the MObile LABoratory (MOLAB) platform of the European Research Infrastructure of Heritage Science.

New insights on impact wear of polycrystalline diamond compact: Effect of interface state on kinetic response and damage behavior

The impact wear of polycrystalline diamond compact (PDC) cutters caused by the discontinuous cutting during the drilling process significantly affects the lifespan and efficiency of the drilling tools. Different PDC impact contact interface states are realized through the selection of impact mating materials. Understanding the effects of different interface states on the kinetic response, damage behavior and impact wear mechanism of PDC is significant in guiding the practical design of material structures with excellent impact wear resistance. Therefore, the kinetic response and damage behavior of PDC impact with different mating materials are investigated. The results show that the kinetic response and damage behavior of PDC are correlated with the mechanical properties of the mating material and physicochemical changes at the impact surface interface. Adhesion and filling resulting from strong covalent bonding and filling effects mitigate the interfacial stress and reduce the average impact force of SiC and Al2O3. Moreover, brittle fracture and filling effects increase the consumption of kinetic energy of SiO2, resulting in an energy absorption of up to 86 %. In addition, the strong covalent bonding effects exacerbated the damage to the PDC interfaces, leading to the internal fracture of diamond particles and detachment at grain boundaries. Furthermore, the filling effect formed plays a specific protective role for diamonds. However, it increases the energy absorption rate and reduces the mating material damage efficiency. In this work, the relationship between impact interface state and impact wear mechanism has been established by understanding the kinetic response, damage morphology, and structural evolution.

Investigation of Gnetum Gnemon and Ramie Natural Fiber on the Mechanical Properties of Composites with the Combination of Aramid and Carbon Fiber as Reinforcement for Military Personnel Applications

Every equipment infrastructure in a TNI unit will be needed to support an operation in the defence system to maintain the integrity of the Unitary State of the Republic of Indonesia. Personal protective equipment is needed for a war operation’s safety or continuity. Protective components made from composite fibers have the advantage of being resistant to corrosion caused by the environment. The natural and carbon fibers will be mixed/reinforced with epoxy resin to become composite materials. This study aims to identify Gnetum Gnemon fiber composites with carbon fiber and aramid fiber to determine the mechanical properties of the composite material resulting from a collision. Natural fiber Gnetum gnemon has not been widely studied as a reinforcing material for polymer composites. Gnetum gnemon fiber chemical composition is hemicellulose approx. 25%, 40% alpha cellulose, 10% lignin and 3-5% benzene extractive. Its density is quite light, 1.2087 g/cm³ - 1.8069 g/cm³. Because this fiber has a continuous fiber structure and a strong natural weave, its use is still minimal. Special treatment such as alkali treatment on Gnetum gnemon, can increase the strength of natural fibers. Due to its exceptional mechanical properties, Kevlar or aramid fibre are extensively used in industrial and military applications. The aramid fiber exhibited a transversely anisotropic nature in a small strain range, with its stress-strain behavior as linear and elastic. The anisotropic nature of the aramid fiber was due to its high tensile-to-shear modulus ratio. The high strength and modulus were also found to be scattered due to the larger distribution of defects in the longer fiber. Epoxy resin is a type of polymer characterized often by one or more epoxide functional groups, with at least one of the epoxide functional groups acting as a monomer and terminal unit of the polymer within the structural chain.

Flexural strength, fracture toughness, translucency, stain resistance, and water sorption of 3D-printed, milled, and conventional denture base materials.

To compare mechanical, optical, and physical properties of denture base materials fabricated with various 3D printing systems to reference milled and conventionally heat-processed denture base materials. Specimens of denture base materials were either 3D-printed (DLP in-office printer, CLIP laboratory printer, or material jetting laboratory printer), milled, or heat processed. 3-point bend flexural strength testing was performed after 50 hours of water storage following 1hour of drying (dry testing) or in 37°C water (wet testing). Fracture toughness was performed with a notched beam specimen after 7 days of water storage and tested dry. The translucency parameter was measured with 2mm thick specimens. Stain resistance was measured as color change following 14 days of storage in 37°C coffee. Water sorption was measured following 7 days of storage in 37°C distilled water. For dry testing, all but one of the 3D-printed materials attained higher or equivalent flexural strength as the reference materials. For wet testing, all 3D-printed materials attained higher or equivalent strength as the reference materials and dry-tested materials. For 3D-printed materials, wet testing increased displacement before fracture whereas it decreased displacement for the reference materials. Only two of the 3D-printed materials had similar fracture toughness as the reference materials. One of the 3D-printed materials was more translucent and one was more opaque than the reference materials. Only one of the 3D-printed materials absorbed more water than the reference materials. 3D-printed denture base materials have mostly equivalent mechanical, optical, and physical properties to conventional and milled denture base materials.

Study of the microhardness ensuring the contact endurance of structural materials

The strength of the working surfaces of gears depends on the mechanical properties of the material and the quality of parts. We present the results of studying the strength of materials and working surfaces of a gear mechanism due to structural changes attributed to chemical and thermal treatment. The surface strength of the gears of gas turbine engines was studied. Nitrocementation and ion nitriding were used for chemical and thermal treatment of the contacting surfaces of steel samples under study (20Kh3MVF-Sh, 16Kh3NVFMB-Sh, 18Kh2H4MA, and 12Kh2H4A). Changes in the microhardness of the component layers (diffusion, transition and basic) of the toothed crown were analyzed. Metallographic analysis of the structure of materials was carried out to describe the factors determining the surface strength of working surfaces. Systematized data on the change in the microhardness of materials obtained experimentally in conditions of mass production are presented. Presented experimental results on changes in the mechanical properties of materials are based on data on the microhardness and structural state of the surface layers of the working profiles of gears. A comparative assessment of the surface strength of the studied samples during contact interaction was performed. The dependence of the surface strength on the multifactorial volumetric structure and structure formation of the material in the process of operation is determined. It is shown that the method of surface saturation forms the structure of a material with different mechanical properties accompanied with the formation of a transition zone having characteristic distinctive values of the hardness. The results obtained can be used in the design of gears, taking into account changes in the mechanical properties and structure of materials to ensure the necessary operational requirements.

The Effects of Laser-Assisted Winding Process Parameters on the Tensile Properties of Carbon Fiber/Polyphenylene Sulfide Composites.

Currently, there is limited research on the in situ forming process of thermoplastic prepreg tape winding, and the unclear impact of process parameters on mechanical properties during manufacturing is becoming increasingly prominent. The study aimed to investigate the influence of process parameters on the mechanical properties of thermoplastic composite materials (CFRP) using laser-assisted CF/PPS winding forming technology. The melting point and decomposition temperature of CF/PPS materials were determined using DSC and TGA instruments, and based on the operating parameters of the laser-assisted winding equipment, the process parameter range for this fabrication technology was designed. A numerical model for the temperature of laser-heated CF/PPS prepreg was established, and based on the filament winding process setup, the heating temperature and tensile strength were simulated and tested. The effects of process parameters on the heating temperature of the prepreg and the tensile strength of NOL rings were then analyzed. The non-dominated sorting genetic algorithm (NSGA-II) was employed to globally optimize the process parameters, aiming to maximize winding rate and tensile strength. The results indicated that core mold temperature, winding rate, laser power, and their interactions significantly affected mechanical properties. The optimal settings were 90 °C, 418.6 mm/s, and 525 W, achieving a maximum tensile strength of 2571.51 MPa. This study provides valuable insights into enhancing the forming efficiency of CF/PPS-reinforced high-performance engineering thermoplastic composites.

Feasibility study on additive-manufactured honeycomb sandwich structural solutions for a Fast Patrol Vessel

This work represents a significant step toward integrating additive-manufactured honeycomb sandwiches into ship hull structures. The sandwich structure consists of two continuous fibre-reinforced thermoplastic faces and a regular honeycomb core made of chopped fibre-reinforced thermoplastic. The primary goal is to create optimal manufacturing and design methods to determine to which extent the sandwich solution that has been analysed may be used as a structural component of a fast patrol vessel. The core of the design procedure is a purposely developed evolutionary multiobjective optimisation routine suited to evaluate the flexural response of the structure under investigation. The analytical formulations utilised to predict the structural response of an additive-manufactured honeycomb sandwich subjected to 3-point bending have been derived using a combined analytical and experimental approach. A fast patrol vessel made of steel has been taken as a reference to demonstrate the capabilities of the proposed solution. A steel primary stiffener and its associated plate have been extracted from the midship section and replaced by an additively manufactured honeycomb sandwich. By maintaining the same structural encumbrances, it has been found that a pseudo-optimal combination of the mechanical properties of the sandwich base materials can accomplish an exceptional weight reduction of three times.

Synergistic reinforcement mechanisms of Cu/graphite composites with MAX phase Ti2AlN and ZrO2-B4C ceramics: Enhancements in mechanical, thermal, and tribological properties

In braking materials field, MAX phase has been introduced into Cu-based composite materials to address issues such as inadequate wetting between ceramic particles and the metal matrix. This study focuses on preparing Ti2AlN-ZrO2-B4C reinforced Cu-based materials via the powder metallurgy method, and investigates the effects and mechanisms of different Ti2AlN/ZrO2 ratios on the mechanical, thermal, and tribological properties of these materials. The addition of an appropriate amount of Ti2AlN (3 wt%) can enhance the densification and mechanical properties of Cu-based materials, as the diffusion of Al atoms promotes the sintering process. Similarly, the diffusion of Al also improves the thermal conductivity at grain boundaries, resulting in samples with higher Ti2AlN content exhibiting superior thermal diffusivity. When the Ti2AlN content reached 7 wt%, the material exhibited optimal hardness (43.35 ± 1.05 HBW), moderate shear strength (19.84 ± 1.86 MPa), as well as excellent high initial braking speed friction coefficient and stability. The reinforcement primarily arises from the diffusion bonding between Ti2AlN and Cu, leading to the formation of Cu-Ti compounds at the interface, which facilitates Ti2AlN in providing frictional force during the friction process and promotes the formation of a friction film due to the “pinning effect”. Additionally, the layered structure of Ti2AlN and the subsequent formation of amorphous Al2O3 after oxidation contributed to the enhancement of friction stability.

Structural Design and Mechanical Properties Analysis of Laminated SiAlON Ceramic Tool Materials

Based on finite element simulation analysis, laminated ceramic tool materials with different structures were designed and the effect of laminated structure on tool state was investigated. Residual stresses in ceramic tool materials increase with the number of layers and layer–thickness ratio. Based on the simulation results, SiAlON-SiC-SiCw/SiAlON-Al2O3 ceramic tool materials (SCWAs) were prepared using the spark plasma sintering process, and the influence of residual stress on the mechanical properties and microstructure of laminated ceramic tool materials was studied. The mechanical properties of ceramic materials were significantly improved under the effect of residual stresses. The fracture toughness of SCWA4 with 7 layers and a layer–thickness ratio of 6 was 6.02 ± 0.19 MPa·m1/2, and the front and side flexural strengths were 602 ± 19 MPa and 595 ± 17 MPa, 36.3% and 39.0% higher than homogeneous SiAlON ceramics, respectively.