Particle Impact Research Articles

Mechanical Characteristics of Sisal/Al<sub>2</sub>O<sub>3</sub>/Epoxy Hybrid Composites

This study examines the impact of Al2O3 particles on composites made of sisal and epoxy. A unique combination of hand lay-up and compression molding procedures are used to fabricate the Sisal/Al2O3/epoxy hybrid composites, with different weight percentages of Al2O3 particles of 0%, 1%, 2%, and 3%. The produced sisal/Al2O3/epoxy hybrid composites' flexural, tensile, and compressive properties are then correlated with water absorption studies. The sisal/epoxy composites have undoubtedly been affected by the Al2O3 particles, which have improved their mechanical and physical properties. Compared to other composite samples, the sisal/2wt.%Al2O3/epoxy hybrid composites show superior flexural, tensile, compressive, and water absorption resistances. Therefore, the optimal combination of hybrid sisal/Al2O3/epoxy composites can prominently improve the properties, making them a viable alternative for a variety of industrial applications.

Experimental and Numerical Investigations of the Sediment Abrasion Mechanism at the Leading Edge of an Airfoil

Multiple engineering projects have confirmed that hydraulic machinery operating in sediment-laden rivers undergoes sediment abrasion. Guide vanes are among the most severely worn flow-passing components and have long been a key research focus in hydraulic machinery. In this research, a wear test of the NACA0012 cascade under a 10° incoming flow angle was carried out in the Venturi test system, and the evolution process of the wear was analyzed. The three-dimensional flow channel of the cascade was constructed, and the Finnie wear model was adopted for computational fluid dynamics (CFD) simulations to analyze the wear mechanism at the initial stage. The results indicate that abrasion primarily occurs at the airfoil’s leading edge and progresses through three stages: initiation, development, and stabilization. The calculated results closely matched the latest wear outcomes: In the initial stage, the wear rate density was influenced by the particle impact velocity, angle, volume fraction, and y-direction shear stress. A low-velocity zone near the impact point, combined with rebounding particles causing secondary impacts, increases the particle volume fraction and wear rate density. These secondary impacts are the primary causes of erosion on both the upstream and downstream surfaces. Furthermore, flow separation downstream from the leading edge makes this region highly susceptible to wear. This study provides valuable insights for addressing wear in hydraulic machinery for practical engineering applications.

Thermophysical and gas dynamics problems of anti-meteorite protection for modern spacecrafts

The results of numerical calculations of the destruction of the protective shields of the spacecraft under the action of a micrometeorite impact are presented. A gas-dynamic numerical simulation of the process of high-speed penetration by micrometeorite of a spaced protective shield of a spacecraft has been carried out, taking into account fragmentation and the formation of a cloud of fragments after passing through the protective shield. In a three-dimensional formulation, the calculated configurations of the cloud of fragments of the impactor and the target for the initial velocities of the impactor up to 10 km/s are obtained. The high efficiency of the used design of a protective screen made of multidirectional corrugated grids as a means of fragmentation and dispersion of the kinetic energy of impact of small high-speed particles, reducing the average pressure pulse on the protected device by two to three orders of magnitude, is shown.

Deposition behavior of the gas-atomized 7075Al and TiB2/7075Al composite powders during cold spraying

To fabricate high-quality coatings or components of high-strength 7075Al alloy by cold spraying, it is essential to understand the impact behavior and bonding mechanisms of the feedstock powder particles. For providing a general comparison, 7075Al powder and TiB2/7075Al composite powder (7075Al alloy matrix reinforced with in-situ formed and uniformly dispersed nano-TiB2 particles) produced by gas-atomization were used as feedstocks in the present study. Single particle impact tests combined with finite element analysis (FEA) were performed on the pure Al and 7075Al-T6 substrates under different process parameter sets. To provide a more realistic description, the real powder strength and plastic parameters obtained by single-particle compression tests were used as input data in the FEA model. The results show that the presence of nano-TiB2 particles has significant strengthening effects on the composite powder, thus resulting in different plastic deformation behavior upon impact compared to 7075Al powder. When the composite particles impacted the soft material (pure Al), the substrate experienced a high degree of deformation, which led to high deposition efficiency due to the embedding effect. Comparatively, the hard substrate (7075Al-T6) was less deformed, whereas the composite particle was highly deformed. Compared to the composite particle, the 7075Al particle presented a slightly higher plastic deformation and pronounced metal jets, which led to a lower critical impact velocity for successful bonding. Interestingly, a fracture was observed at the grain boundaries of both 7075Al and TiB2/7075Al composite particles in the case of a high gas temperature regime, which probably revealed that the high shock energy associated with high-velocity impact led to such intergranular fracture.

Erosion characteristics and mechanisms of different particle sizes under the synergy effect of cavitation and particle erosion

Particle erosion, particularly the mechanism whereby erosion occurs under the synergy of cavitation and particle impact, is a critical area of research in hydraulic machinery. This study investigates the influence of particle size on the erosion characteristics under the synergistic action of cavitation and particle erosion through turntable erosion experiments and numerical simulations. The findings indicate that cutting erosion is dominant under these combined conditions, with a clear overlap between high-erosion-rate regions and high-speed-impact areas. For particle sizes ranging from 0.2–0.6 mm, the maximum erosion rate increases significantly. When the particles are larger than 0.6 mm, smaller-diameter particles correspond to higher impact angles, while larger-diameter particles encounter lower impact angles due to their increased inertia. Moreover, cavitation greatly influences the movement and acceleration of the particles, especially as the angle of the cavitation inducer increases, leading to a marked rise in acceleration. This study enhances the understanding of particle erosion under cavitation conditions, underscores the crucial role of cavitation in the erosion mechanism, and provides a theoretical foundation for optimizing erosion performance and guiding future research directions.

3D Printed hybrid rocket fuels with μAl core-shell particles coated with polyvinylidene fluoride and polydopamine: enhanced combustion characteristics

3D printing technology enhances the combustion characteristics of hybrid rocket fuels by enabling complex geometries. However, improvements in regression rate and energy properties of monotonous 3D printed fuels have been limited. This study explores the impact of poly (vinylidene fluoride) and polydopamine-coated aluminum particles on the thermal and combustion properties of 3D printed hybrid rocket fuels. Physical self-assembly and anti-solvent methods were employed for constructing composite μAl particles. Characterization using SEM, XRD, XPS, FTIR, and μCT revealed a core-shell structure and homogeneous elemental distribution. Thermal analysis showed that PVDF coatings significantly increased the heat of combustion for aluminum particles, with maximum enhancement observed in μAl@PDA@PVDF (denoted as μAl@PF) at 6.20 kJ/g. Subsequently, 3D printed fuels with varying pure and composite μAl particle contents were prepared using 3D printing. Combustion tests indicated higher regression rates for Al@PF/Resin composites compared to pure resin, positively correlating with particle content. The fluorocarbon-alumina reaction during the combustion stage intensified Al particle combustion, reducing residue size. A comprehensive model based on experiments provides insights into the combustion process of PDA and PVDF-coated droplets. This study advances the design of 3D-printed hybrid rocket fuels, offering strategies to improve regression rates and energy release, crucial for enhancing solid fuel performance for hybrid propulsion.

Preparation and properties of a fluorine-free aerogel foam extinguishing agent

Research on fluorine-free firefighting foams is urgently needed due to the environmental hazards of conventional aqueous film-forming foams. Functional particles have significant research potential in the development of fluorine-free foam extinguishing agents. In this study, hydrophobic aerogel particles were prepared using a template method, and a fluorine-free aerogel foam extinguishing agent was developed by electrostatic and steric stabilization. The research investigated the impact of aerogel particles and polymers (xanthan gum and polyethylene glycol) on foam characteristics, fire extinguishing performance, as well as their synergistic effect. The results indicated that polymers and aerogel particles reduced the average foam radius and enhanced the foam liquid film strength, though they could not inhibit foam coarsening. Although accelerating foam drainage, aerogel particles effectively enhanced the fire extinguishing performance of the foam. With the addition of only 0.4wt.% aerogel particles, the fire extinguishing time of the foam was reduced by 21.7%, while 100% burnback time increased by 45%. Furthermore, the polymer enhanced the burnback performance of the foam in synergy with aerogel particles by improving foam stability on the hot heptane surface.

Effect of particle impact on spatial and temporal erosion characteristics of turboshaft engine compressor

When turboshaft engines operate in dusty environments, particulate matter erodes the compressor blades, which may leads to structural damage and presents a severe threat to the operational reliability and safety of helicopters. The aim of this study is to determine the erosion characteristics of compressor blades and how it changes with time. Particle velocimetry and erosive experiments were conducted to obtain the SiO2 particle velocity and the erosion rate of the Ti-6Al-4V titanium alloy. Based on the measured data, the parameters of the Tabakoff erosion model have been refined, which is critical for establishing a transient erosion model for the 1.5-stage compressor of a turboshaft engine that accounts for the effect of particle erosion time. Simulation results show that the motion behaviour of particles exhibits changing patterns at different time intervals, which leads to variations in the erosion area and erosion rate of the compressor. The erosion area and rate on blades increase nonlinearly with time. In some locations, when erosion time increases, the erosion area and erosion rate also increase. While, in other locations, the erosion area and erosion rate hardly change with time. The maximum erosion rates increased by 27.3%, 28.6%, and 87.2% for the guide blades, 42.9%, 69.6%, and 84.0% for the rotor blades, and 69.0%, 103.6%, and 142.8% for the stator blades at 0.50s, 0.75s, and 1.00s, respectively, in comparison to 0.25s.

Controls on Erosion and Cyclic Step-Formation Upstream of Waterfalls.

Waterfall retreat transmits base-level perturbations upstream, thereby providing markers of changing climate and tectonics. In homogeneous rock, waterfalls often retreat either by direct waterfall-face erosion or incision from repeating ('cyclic') steps formed above waterfalls. We lack knowledge on the conditions driving these different erosion styles, limiting our ability to predict waterfall retreat. We address this knowledge gap through flume experiments assessing how changing flow hydraulics modulates bedrock erosion. We show that, under large discharges, changes in flow hydraulics cause spatial variability in particle impact velocity, leading to cyclic step formation. As discharge decreases, both the magnitude and spatial variability of particle impact velocity decreases, causing more uniform erosion, limiting cyclic step development and potentially allowing direct erosion of the waterfall face to become the dominant retreat mechanism. These results suggest climate change and water-resource management can alter the rate and style of waterfall retreat.

Erosion behavior of Al–SiC and Al–WC MMCs via powder metallurgy under solid particle impingement

This study investigates the erosion behavior of Al–SiC and Al–WC metal-based composites in a solid particle impingement environment developed through powder metallurgy. Micro-sized powders of SiC and WC were utilized in different weight proportions (0–10 wt%) for fabricating the composite samples. The angle of impingements of 30–90° and impact velocity of 30–90 m/s were used for solid particle erosion testing. Microstructure was characterized by XRD, SEM, and EDS. The results of the ANOVA test indicate that impact velocity is the most significant factor, followed by reinforcement content. SiC composite with reinforcement content of 2.5 and 5 wt% showed ductile erosion behavior at lower angles of impingements and brittle behavior at higher angles of impingements. On the other hand, 10 wt% of SiC indicated a semi-ductile erosion behavior. The reinforcement content is 5 and 10 wt % of WC showed a semi-ductile erosion behavior, whereas 2.5 wt% of WC showed a mix of ductile and brittle behavior. At a 30° angle of impingement, SiC (10 wt%) provides the best erosion performance, whereas, at 90° (i.e., at normal), WC (10 wt%) performs better than all other composites. SiC (5 wt %) comes out to be the best performer at 45° of the angle of impingement.

Study of erosion wear by solid particle of a PMMA/SiO2 hybrid coating with graphene oxide applied on a composite laminate

This study reports the tribological performance of a family of PMMA/SiO2 hybrid coatings with graphene oxide applied on composite laminate substrates. The transformation from graphite to graphene oxide was carried out using a high-energy mill for 90 minutes. The composite laminates of epoxy resin matrix and layers of bidirectional carbon fiber were obtained through the vacuum infusion process. The coatings were applied on the composite laminates using the dip-coating method. To disperse the graphene oxide in the hybrid solutions, an ultrasonic bath (40 kHz) was used during the immersion of the substrate. Tribological tests of erosive wear by solid particle impact (beach sand) were performed on a horizontal erosion test platform under conditions of pressure of 45 psi, impact velocity of 6 m/s, distance between nozzle and specimen of 10 mm and impact angle of 90°. The results showed that coatings with graphene oxide increase their protection against erosion by 50 (9-PMMA/1-SiO2-2GO) to 54% (9-PMMA/1-SiO2-1GO) more than the coating without graphene oxide. The results obtained could be considered for using this type of coating as an alternative protection on the leading edge of wind turbine blades that are exposed to conditions of erosion wear by solid particle impact.

Covalent Organic Frameworks with Constrained Palladium Nanoclusters Lock the Enol-Keto Tautomerism Enhancing Hydrogen Peroxide Photosynthesis.

The production of hydrogen peroxide from natural seawater is green and sustainable. However, the efficiency of photocatalytic hydrogen peroxide production is low due to the degradation and poisoning of photocatalysts by the abundant ions in natural seawater. Precisely controlling the structure of photocatalysts to enhance their corrosion resistance and minimize the impact of external particles is a challenging task. Here, a novel molecular engineering strategy is reported in which confined Pd nanoclusters locked keto structures to enhance photocatalytic hydrogen peroxide production. Both experimental and theoretical findings reveals that Pd nanoclusters, when confined within a keto structure, not only bolster the stability of the photocatalyst but also augment the efficiency of photogenerated charge carriers' separation and transport. This dual enhancement significantly boosts the photocatalytic performance for hydrogen peroxide synthesis. One of the photocatalysts, TAPT-2KtTb Pd COF, exhibits an impressive photocatalytic hydrogen peroxide production rate of 2676.3µmol g-1 h-1, which is one of the highest values reported so far. Integral photocatalyzed H2O2 synthesis using confined Pd nanoclusters locked keto conformation COF provides a new insight for developing innovative photocatalysts for H2O2 synthesis.

Modeling the interstellar dust detections by DESTINY[formula omitted] I: Instrumental constraints and detectability of organic compounds

The DESTINY+ spacecraft will be launched to the active asteroid (3200) Phaethon in 2025. The spacecraft will be equipped with the DESTINY+ Dust Analyzer (DDA) which will be a time-of-flight impact ionization mass spectrometer. In addition to the composition of impacting dust particles, the instrument will measure the particle mass, velocity vector, and surface charge. Here, we study the detection conditions of DDA for interstellar dust during the DESTINY+ mission. We use the interstellar dust module of the Interplanetary Meteoroid environment for EXploration model (IMEX Sterken et al., 2013; Strub et al., 2019) to simulate the flow of interstellar dust through the Solar System. Extending earlier work by Krüger et al. (2019b) we consider the entire DESTINY+ mission, i.e. the Earth-orbiting phase of the spacecraft during the initial approximately 1.5 years after launch, the nominal interplanetary mission phase up to the Phaethon flyby, and a four-years mission extension beyond the Phaethon flyby. The latter may include additional asteroid flybys. For predicting dust fluxes and fluences we take into account a technical constraint for DDA not to point closer than 90° towards the Sun direction for health and safety reasons of the instrument and in order to avoid electrical noise generated by photoelectrons. For the Earth orbiting phase after launch of DESTINY+ our simulations predict that up to 28 interstellar particles will be detectable with DDA in 2026. In the following years the interplanetary magnetic field changes to a focussing configuration for small (≲0.1μm) interstellar dust particles. This increases the total number of detectable particles to 50 during the interplanetary mission of DESTINY+ in 2027. In 2028 and 2029/30 approximately 160 and 190 particles will be detectable, respectively, followed by about 500 in 2030/31. We also make predictions for the detectability of organic compounds contained in the interstellar particles which is a strong function of the particle impact speed onto the detector. While organic compounds will be measurable only in a negligible number of particles during the Earth orbiting and the nominal interplanetary mission phases, a few 10s of interstellar particle detections with measurable organic compounds are predicted for the extended mission from 2028 to 2031.

Impact of magnesium hydroxide particles decorated Kenaf fibre on the physico-mechanical properties of polypropylene-based composites

Impact of magnesium hydroxide particles decorated Kenaf fibre on the physico-mechanical properties of polypropylene-based composites

THE EROSIVE WEAR OF GRAPHENE OXIDE REINFORCEDEPOXY POWDER COATINGS

Powder coatings are organic coatings that protect the metal substrate against corrosion and wear, and playa decorative role. The doping of paints with nanoparticles is intended to create a barrier to corrosive andchemical agents and to increase abrasion resistance. This work tested the erosion resistance of epoxy powdercoating with graphene oxide flakes and polyethylene wax covered with a layer of micro diamonds. Twomethods of testing resistance to abrasive wear were used, in which the conditions are similar to operatingconditions: solid particle impingement (sandblasting) and barrel finisher with ceramic shapes. Mass loss dueto erosion in a sandblaster using glass beads with a diameter of 200 μm for the paint with graphene was muchlower than for the reference sample. The mass loss of the samples was tested after 15, 30, and 60 seconds ofabrasive jet operation. The surface texture was analyzed during the process and after the test. The test in thebarrel finisher was carried out twice for different times: for the first series weight loss was measured after 30,90, and 210 minutes, for the second Vickers hardness at 40 g load after 90 and 210 minutes. The tests showedthat the epoxy coating with the addition of graphene oxide has a much higher resistance to erosion under theinfluence of an abrasive stream than the reference paint, and a similar resistance to erosion in a containersmoother. It was found that the paints showed a higher Vickers hardness after the wear test.

Modelling of particle-reflection-distributions of rough surfaces

The modelling of plasma-wall-interactions (PWI) depends on distributions describing the angle- and energy distribution of particles scattered at first wall. Most PWI codes (e.g. SOLPS, EIRENE) rely on extensive tables based on reflection simulations (e.g. SDTrimSP-1D) or analytical formulae. However, both approaches assume an atomistically flat (smooth) surface. Rough surfaces which are formed under particle impact typically display a very different particle distribution compared to smooth surfaces. However, roughening is almost unavoidable, e.g. due to preferential sputtering, crystal-orientation dependent sputtering, precipitates, or thermal cycling. In this paper we investigate the effects of roughening on the reflection distributions using W- and W-Fe-surfaces of different morphologies within the binary collision approximation by SDTrimSP-2D.

Subsurface Weave Pattern Influences on Polymer Cold Spray Deposits onto Woven Fiber-Reinforced Composites

AbstractThe polymer cold spray (CS) process has recently been demonstrated as a promising coating and repair technique for fiber-reinforced polymer composites (FRPs). However, a noticeable variation in coating thickness (herein referred to as checkerboard pattern) often occurs in the initial pass of low-pressure CS deposition. The checkerboard pattern occurs due to the periodic variations in matrix thickness and volume above the subsurface fiber weave pattern. When the initial pass exhibits the so-called checkerboard pattern, the CS deposition for subsequent passes may be negatively affected in terms of deposition efficiency, porosity, adhesion, surface roughness, and thickness consistency. The present work compares results of both numerical simulations and experimental studies performed to reveal the governing mechanisms for and elimination of checkerboarding. Single particle impact numerical simulations are conducted to observe thermomechanical behavior of particles during CS impact on the FRP surface at different regions of the composite material. Complementary experimental CS studies of exemplar powders onto FRPs with various surface interlayer thicknesses are also presented and discussed. Experimental analyses of deposits include microstructural observations to compare against the simulations while also providing practical strategies for the elimination of checkerboarding effects. It is demonstrated that the thickness and volume of the matrix region underneath the impact area are the main contributing factors that govern the CS deposition variations on CFRP substrates. As such, increasing the surface epoxy layer thickness beyond a critical value can reduce the effect of substrate stiffness effects imposed by the subsurface fiber tows, thereby effectively eliminating the checkerboard patterns.

Investigating the Impact of Nano‐Metal Oxides (Copper and Iron) on the Thermal Decomposition Behavior of Advanced Propellants with Nitrocellulose/Polyurethane Binders

AbstractThis research delves into the combined effects of green nano metal oxides (copper and iron) and polyurethane (PU) modification on the thermal degradation kinetics of propellant based on solid ammonium nitrate composite modified simple base (CMSB). Surface modification of ammonium nitrate particles was achieved through repeated spray coating, ensuring effective catalyst binding. The formulated compositions of propellants underwent thorough thermal characterization, including thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses. TG analysis revealed a significant decrease in the propellant's thermal degradation temperature, attributed to AN modification with nano metal oxides (nMOs) and the use of PU/NC as a binder. Isoconversional kinetic methods (It‐KAS, It‐FWO, and VYA/CE) were employed for further analysis, allowing prediction of kinetic parameters. Additionally, kinetic analysis results allowed calculation of the critical ignition temperature. The thermokinetic results underscore the substantial impact of nMOs particles and PU modification regarding the reactivity and catalytic performance of propellant containing ammonium nitrate, leading to a noteworthy reduction in activation energy and critical ignition temperature. Furthermore, modifying the binder with nitrocellulose and incorporating nanoparticles significantly reduces ignition delay and combustion duration while increasing flame intensity in CMDB solid propellants, enhancing overall combustion efficiency.

Low-temperature preparation of C/C-W-Cu composites with enhanced particle impact and ablation resistance

Herein, C/C-W-Cu composites were innovatively developed by a molten salt assisted reactive infiltration method, with the preparation temperature of only 1300 ℃, far lower than the traditional infiltration temperatures. The as-prepared C/C-W-Cu composites exhibited better particle erosion and high-temperature ablation resistance than C/C composites, with a linear variation rate decrease of 99.5 % and 80.3 % under particle impact (70 m/s, 10 s) and oxyacetylene ablation (2.4 MW/m2, 120 s) conditions, respectively. The improved protection performance can be attributed to the synergistic effects of ductile deformation of the surface W-Cu metal layer and transpiration cooling of the filled Cu phase, which prevents serious carbon fiber damage and ensures a low response of surface ablation temperature (∼1400 ℃).

Impact of Graphene Nano particles on static and dynamic mechanical properties of basalt-glass fibre reinforced epoxy polymer hybrid composites

ABSTRACT This paper investigates the structure-property relationships in basalt – glass fabric reinforced hybrid polymer composites doped with graphene nanoplatelets. Basalt Glass fabrics were reinforced with 0.2 wt.% − 0.8 wt.% graphene using hand layup and compression moulding to fabricate laminated plates. The mechanical, morphological, and thermomechanical properties were characterised using tensile, flexural, impact, SEM, FTIR, XRD, and DMA testing. Results showed that low graphene loadings of 0.2 wt.% − 0.4 wt.% led to small, isolated graphene platelets decorating the basalt fibres. At 0.8 wt.% loading, extensive wrinkling, folding, and stacking of graphene sheets on the basalt was observed. FTIR revealed increasing sp2 C=C vibrations and XRD showed rising graphene peak intensities with higher loadings. While tensile and flexural strengths improved up to 0.6 wt.% graphene due to efficient stress transfer, impact energy increased consistently until 0.8 wt.% graphene owing to reinforcement effects. DMA exhibited enhanced storage modulus and restricted mobility with more graphene. An optimum graphene loading of 0.6 wt.% was found to maximise the mechanical performance through uniform dispersion and strong interfacial adhesion. The results demonstrate that graphene incorporation can substantially augment the strength, toughness, and thermomechanical properties of the composites at appropriate compositions prior to aggregation.