Glass Microballoons Research Articles

Vat photopolymerization 3D printing of glass microballoon-reinforced TPMS meta-structures

Advancements in additive manufacturing coincide with the influx of assiduous research in realizing complex structures using printable composite materials with tunable properties. In this research study, photocurable resins with a broad range of mechanical properties were hybridized with ceramic particles to engineer the overall mechanical response. The newly formulated printable resins comprised up to 20 wt.% glass microballoons, balancing the tunability of the composite properties and manufacturability by overcoming light-reinforcement challenges. The compressive and tensile bulk properties were first assessed using additively manufactured samples tested under quasi-static loading. Complementary digital image correlation (DIC) was used to resolve the strain fields, revealing insights about the mechanical behavior and failure modes as a function of reinforcement weight ratio. Despite the expected hyperelastic constitutive behavior and shared macromolecular composition, the neat and hybridized photocurable resins exhibited distinctive mechanical behavior, leading to the characterization of the dynamic properties as a function of temperature to ascertain the underpinnings of respective responses. Triply periodic minimal surface (TPMS) structures were also manufactured using the vat photopolymerization approach to demonstrate the utility of newly formulated printable composite resins. The printed structures were tested under compression at a quasi-static loading rate. The DIC-resolved strains revealed the underlying structural mechanics as a function of the material properties. This case study correlates the mechanics governing particulate-reinforced elastomers with the observed variations in strain development, stiffness, load-bearing capacity, and specific energy absorption for TPMS structures. Finite element analysis (FEA) based on hyperelastic potential and using the properties of the bulk resin closely matched the deformation patterns from the experimental DIC results. The outcomes of this research reveal the potential for tunable, 3D printed sports gear for impact mitigation in various biomechanical loading conditions.

Mechanism of hot‐spot formation of emulsion explosives sensitized by hydrogen‐storage glass microballoons

AbstractIn order to investigate the primary factors influencing hot‐spot formation in emulsion explosives sensitized by hydrogen‐storage glass microballoons (GMBs), we conducted impact calculations on hydrogen‐storage GMBs. The calculations focused on tracking two main mechanisms: the brittle collapse of GMBs and the adiabatic compression of internal gas. Various parameters were considered, including loading pressures, initial porosities, gas types, and initial gas pressures. Our findings indicate that the contribution of brittle collapse to hot‐spot formation is negligible, while adiabatic compression emerges as the predominant intrinsic mechanism for hot‐spot ignition in GMB‐sensitized emulsion explosives. Moreover, we observed that the ignition time remains similar for low‐pressure nitrogen and high‐pressure hydrogen. The addition of hydrogen does not result in an increased number of hot‐spots; however, it elevates the energy of each individual hot‐spot, thereby enhancing power delivery. Optimal selection of GMB size is crucial for hot‐spot formation and hydrogen storage. GMBs that are excessively large are prone to shell breakage, while overly small GMBs have limited hydrogen storage capacity. GMBs within the size range of 20 μm to 100 μm are deemed more suitable for emulsion explosives.

CONSERVATION OF A PAINTED WOODEN COFFIN AT DAHSHUR ARCHAEOLOGICAL AREA

This paper aims to document the conservation processes of a polychrome wooden coffin in the Dahshur archaeological area dating back to the late period. The exterior part of the coffin is decorated with a painted layer. Visual observation, 2D Program, and Optical Microscopy (OM) were used. wood identification. The coffin was in a bad condition. It was covered with a thick layer of dust, losing parts of the painted and gesso layers, as well as other parts of these layers, were lost. Some parts were missing from the head area of the lid coffin. The conservation processes of the wooden coffin included mechanical and chemical cleaning, reattachment of the separated parts of the ground layer and painted layers, filling the edge of the painted layer, and consolidating the painted layer. The conservation process included mechanical cleaning using soft brushes, chemical cleaning using ethyl alcohol and distilled water for painting, stabilization of the separated gesso layer using Paraloid B72, filling cracks of the gesso layers using glass microballoon with Paraloid B72 and consolidating the painted layer with calcium oxide nanoparticles with Klucel G (hydroxypropyl cellulose) 0. 5%

Detonation parameters of the mixture of gelled nitromethane/microballoons at high porosity

The detonation properties of mixtures of gelled nitromethane (NM) with hollow glass microballoons (GMBs), the concentration of which varied from 16 to 30 wt. %, have been studied using an optical technique with high temporal and spatial resolution. It is shown that the addition of GMBs up to 30 wt. % does not qualitatively change the reaction zone structure of NM, which is in accordance with the classical detonation theory. However, the detonation parameters of the mixture decrease significantly with increasing GMB concentration—the pressure at the Chapman–Jouguet point drops by more than an order of magnitude at a porosity of 75%. The non-monotonic nature of the change in critical detonation diameter with decreasing mixture density is noted. The dependence of the critical diameter on the porosity of U-shape with the formation of two local minima at 8 and 18 wt. % GMB in the mixture and a local maximum at 13 wt. % GMB is obtained. At a concentration above 20 wt. % GMB, the critical detonation diameter increases dramatically, and at 30 wt. % GMB, the critical diameter becomes comparable to that of gelled NM.

Full-field characterizations of additively manufactured composite cellular structures

Honeycomb structures possess unique mechanical and structural behaviors, including high specific strength, superior energy absorption, and potential for multifunctionality. The advantages of such structures are bolstered by their realization through additive manufacturing, enabling cellular geometries beyond traditionally fabricated hexagons and facilitating a pathway for hybridization using composite materials to tune the response. This research synthesized photocurable, particulate-reinforced resins using mechanically compliant matrix and glass microballoons reinforcement. The modified resins were used to additively manufacture lattice structures with circular and hexagonal unit cell geometries at different glass microballoons reinforcement weight ratios, ranging from neat to 20 wt.%. The 3D printed structures were tested under quasi-static and impact loading scenarios to elucidate the interrelationships between the cell geometry, induced deformations, and strain rates. The mechanical testing was coupled with digital image correlation (DIC) to reveal the deformation-geometry interrelationship on the global (macroscale) and local (mesoscale) levels. The multiscale analyses allowed for extensive characterization of the effect of cell geometry and increased weight reinforcement on the mechanical response at a global, sub-cellular, and cellular level, i.e., elucidating the hierarchical dependency. The novelty leading to the current study stems from probing and revealing the deformation state of cellular structures subjected to two loading scenarios using DIC. This study intended to provide mechanistic insights for engineering lattice structures for impact mitigation applications by offering a viable approach to additive manufacturing composite materials.

CONSERVATION PROCESSES OF A WOODEN COFFIN COVERED WITH A BLACK RESIN LAYER AND COLORED MATERIALS IN DAHSHUR ARCHAEOLOGICAL AREA

This paper describes the results of a multi-technological analytical protocol performed on the painted surface of an Egyptian wooden coffin and documents the conservation processes of a wooden coffin covered with a black resin layer and coloured materials in Dahshur Archaeological Area dating back to the late period. It uses visual observation, optical microscopy (OM), technical imaging, 2D and 3D programmes, and a scan made using an electron microscope coupled with an Energy Dispersive X-ray (SEM-EDX), X-ray diffraction (XRD). Wood identification was also carried out. The results showed the use of yellow ochre for the yellow painted layer; the ground layer was calcium carbonate with gypsum, and the fabric layer was linen. The conservation processes of the wooden coffin included mechanical and chemical cleaning; reassembling the separated wooden parts, ground layer, and black resin layers; filling the edge of the ground layer; and consolidating the wood, black resin, and painted layer. The conservation processes included mechanical cleaning using soft brushes, chemical cleaning using xylene and distilled water for the black resin layer and ethyl alcohol and distilled water for the painted layer, stabilisation of the separated ground layer using Paraloid B72, filling the cracks of the ground layers using glass microballoons with Paraloid B72, and consolidating the painted layer with nano-silica with Klucel G (hydroxypropyl cellulose) (0.5% concentration).

Structural Performance of Additively Manufactured Composite Lattice Structures: Strain Rate, Cell Geometry, and Weight Ratio Effects

The proliferation of ordered cellular structures in industrial and technological applications is justified by their superior mechanical performance, including tunable energy absorption strategies and potential multifunctionality. This research evaluates the mechanical response of composite lattice structures fabricated using vat photopolymerization additive manufacturing process and printable particulate composite materials. Several generations of modified printable resins are prepared by hybridizing flexible resin with varying glass microballoons reinforcement weight percentages. Multifaceted characterization regiments highlight the process–property–performance interrelationship by submitting printed composite structures to quasi‐static and impact‐loading scenarios combined with digital stills and high‐speed photography, respectively. Image analyses of optical and scanning electron micrographs quantify the dimensional accuracy of the composite lattice structures with cylindrical and hexagonal cellular geometries. The mechanical characterization uncovers the effect of cell geometry and reinforcement on the global structural behavior, eliciting differences in load‐bearing capacity, local strain developments, and structural densification. Exploratory digital image correlation supports the global structural deformations, revealing their relationship with the developed local strain state within the unit cells. The outcomes of this research elucidate the effect of strain rate, unit cell geometry, and reinforcing ratios on the structural performance of composite lattice structures at the macro‐ and microstructure levels.

An Insight into Microstructure and Mechanical Response of Mg-Li-Based Composites Prepared Using Glass Microballoons as Starting Reinforcement

An Insight into Microstructure and Mechanical Response of Mg-Li-Based Composites Prepared Using Glass Microballoons as Starting Reinforcement

Moisture-driven degradation mechanisms in the viscoelastic properties of TPU-Based syntactic foams

Syntactic foams have found widespread usage in various applications including, marine, aerospace, automotive, pipe insulation, electrical cable sheathing, and shoe insoles. However, syntactic foams are often exposed to moisture when used in these applications that potentially alter their viscoelastic properties, which influences their long-term durability. Despite their significance, previous research has mainly focused on experimental studies concerning mechanical property changes resulting from filler loading and different matrix materials, overlooking the fundamental mechanisms resulting from moisture exposure. The current paper aims to bridge this gap in knowledge by elucidating the impact of long-term moisture exposure on TPU and TPU-based syntactic foam through multi-scale materials characterization approaches. Here, we choose a flexible syntactic foam manufactured using thermoplastic polyurethane elastomer (TPU) reinforced with glass microballoons (GMB) through selective laser sintering. Specifically, the research investigates the influence of moisture exposure time and the volume fraction of GMB on chemical and microphase morphological changes, along with their associated mechanisms. The study further examines how these microphase morphological changes manifest in viscoelastic properties.

Characterization of dynamic confinement response of potting materials at different strain rates and temperatures

A Kolsky compression bar was modified with an instrumented confining tube for characterizing dynamic confinement response of materials at various strain rates. A thin film polyvinylidene fluoride (PVDF) force transducer was designed and integrated to the confining tube for direct in-situ measurement of confining pressure when the specimen is subjected to dynamic axial compressive load such that the mean stress-volumetric strain response of the specimen material is able to be determined. An environmental chamber was also implemented to the Kolsky compression bar for characterizing dynamic confinement response of materials at different environmental temperatures. After careful calibration of the instrumental confining tube, five different potting materials (EPON 828, EPON 828 filled with glass microballoons (GMBs), Sylgard 184, Sylgard 184 filled with GMBs, and expanded polystyrene (EPS) foam) were characterized with the modified Kolsky compression bar at different strain rates and environment temperatures. The effects of strain rate and temperature on the mean stress-volumetric strain response were determined for all five potting materials. Experimental uncertainties were also presented.

Modifying explosive behavior with additives

AbstractThe influence of additives on the detonation velocity of a polyethylene wax/RDX formulation was examined. Additives included species of various shock impedance: glass microballoons; glass microspheres; polymethyl methacrylate (PMMA) microspheres; thermally expandable microspheres (TEMs); and PMMA microencapsulated pentaerythritol tetranitrate (PETN). Performance of the insensitive explosive 2,4‐dinitroanisole (DNAN) was enhanced by addition of PETN‐either neat or encapsulated, but encapsulation did not increase the sensitivity of the formulation. The energy contribution of the encapsulated PETN to the detonation front of the insensitive explosive 2,4‐dinitroanisole (DNAN) was also demonstrated. Present in 5 wt%, the encapsulated PETN allowed DNAN to sustain a reaction (5.36 km/s) at 13 mm, well below its critical diameter.

3D printed functionally graded foams response under transverse load

The applications of 3D printing are rapidly increasing in aerospace and naval applications. Nonetheless, 3D printing (3DP) of graded foams exhibiting property variation along the thickness direction is yet to be explored. In the current work, the different volume fractions of hollow glass micro balloon (GMB) reinforced high-density polyethylene (HDPE) composite based graded foams are 3D printed using the fused deposition modelling (FDM) technique. The bonding between successive layers and porosity distribution of these graded configurations are studied using micro-CT scan. Further, the 3D Printed functionally graded foams (FGFs) are tested for flexural response, and results are compared with numerical values. The micro-CT results showed delamination absence between the layers. In neat HDPE layers, porosity is not evident, while minor porosity creeps in the layers having the highest GMB content. Experimental results of the flexural test showed that the graded sandwiches exhibited better strength than the graded core alone. Compared to neat HDPE, the modulus of FGF-2 (H20–H40–H60) increased by 33.83%, implying better mechanical stiffness. Among all the FGFs, FGF-2 exhibited a better specific modulus. A comparative study of experimental and numerical results showed a slight deviation due to neglecting the induced porosity.

Modeling and analysis of K15 hollow glass microballoons filled epoxy syntactic foam for lightweight structures

Modeling and analysis of K15 hollow glass microballoons filled epoxy syntactic foam for lightweight structures

Multi-objective optimization of machining parameter in laser drilling of glass microballoon/epoxy syntactic foams

The effect of CO2 laser drilling on glass microballoon/epoxy syntactic foams are investigated in this study to optimize machining parameters to achieve a clean hole for various industrial applications. The epoxy matrix is reinforced with glass microballoons in concentrations of 0, 20 and 40 vol%. Cutting speed, laser power and additive percentage are input parameters for optimization. Kerf taper angle, surface roughness and ovality percentage are used as output responses to evaluate hole quality. For the optimization study, hybrid multi-criteria decision-making methods such as grey relational analysis and multi-objective optimization with ratio assessment methods are used, with equal weightage given to each output response. According to the study, low power and high speed produce better machining results such as a smaller kerf taper angle, lower surface roughness and a lower ovality percentage. Furthermore, a higher additive percentage is not appropriate for laser in epoxy/glass microballoon composite because it burns the area near the laser and increases surface roughness.

Effect of charge diameter on detonation parameters in the mixture of gelled nitromethane/microballoons

In this work, the detonation wave structure and detonation parameters of mixtures of gelled nitromethane (NM) with hollow glass microballoons (GMBs) are investigated with a laser velocimetry technique. It is shown that the addition from 0.5 to 13 wt. % GMB with the mean diameter of 70 μm does not qualitatively change the reaction zone structure of gelled NM, and it corresponds to the Zeldovich–von Neumann–Döring theory, predicting the formation of the von Neumann spike. The detonation parameters of the explosive mixture monotonically decrease—in particular, the ideal detonation velocity drops from 6.3 km/s for gelled NM to 3.7 km/s for its mixture with 13 wt. % GMB. The addition of GMB leads to a significant reduction in the critical detonation diameter, which decreases from 16.5 mm in gelled NM to 3.5 mm in the mixture with 8 wt. % GMB. The influence of polymethylmethacrylate concentration in the mixture of gelled NM with GMB on the value of critical diameter of the mixture is observed.

EFFECT OF MICRO-BALLOON VOLUME FRACTION ON THE TENSILE BEHAVIOR OF EPOXY SYNTACTIC FOAMS REINFORCED WITH GLASS MICRO-BALLOONS

In this study, the effects of volume fraction on the tensile behavior of epoxy syntactic foam reinforced with glass micro-balloons are investigated. Nine different samples with various volume fractions of glass micro-balloons (0%-68%) were prepared. Elastic modulus, maximum tensile stress, and strain at failure of epoxy syntactic foams reinforced with glass micro-balloons are investigated. Scanning electron microscope (SEM) images are taken from the broken samples' surfaces and used to discuss the results. Results show that the specific elastic modulus and specific maximum tensile stress (MTS) of epoxy syntactic foams increased by about 108% and 28% by increasing the micro-balloon volume fraction from 0% to 68%. However, the samples' modulus and strength are respectively decreased by about 5% and 39% with increasing the volume fraction of the glass micro-balloons from 0% to 34%. The main growth of specific strength and elastic modulus was for samples with more than 34% micro-balloon volume fraction. Moreover, the elastic modulus increased by about 11%, and the samples' maximum tensile stress (MTS) decreased by about 32%, increasing the micro-balloon volume fraction from 0% to 68%. With increasing the micro-balloon volume fraction from 0% to 68%, the strain at failure of epoxy syntactic foams is decreased by about 41%.

Influence of surfactant on foam generation and stabilization in cement slurry

Modern civil engineering and industrial buildings use foamed cement because of its low heat conductivity and light weight.Despite their high performance, foamed cement products manufactured solely from cement might be prohibitively expensive for commercial entities. Thus, chemically foaming cement is important. This paper compiles and reviewsthe foamed cement preparation, mostly used physical and chemical foaming processes. Physical foaming creates foamed cement by mixing foam into a slurry. Physical foaming methods are inefficient and energy-intensive. Chemical foaming involves adding a foaming ingredient to cement slurry. Foaming agents like surfactants react to create bubbles that expand the slurry. Surfactants in the liquid solution promote a bubble by spontaneously cicatrizing holes caused by external perturbations. These chemicals stabilize foams and bubbles for minutes to hours. Oil and gas well cementing uses Self-generated nitrogen foam cement (SNFC) with a high-efficiency foam stabilizer. Three surfactants produced cement pastes with and without MWCNT. A viscosity-modifying agent (VMA) in an aqueous cement paste dispersion can change its rheology. Sodium dodecyl sulfate (SDS) and CaCl2 increase nanosilica (NS) fluidity for pumping cement-based grout. FSCGM is used for coal mine infill grouting. Foamed sulfoaluminate cement-based grouting material (FSCGM) makes firefighting CO2 foam. Cement-hollow glass microballoon syntactic foams have greater compressive strength than neat cement at equal densities. Polydentatephosphonate-modified polymers and ester-type polycarboxylate superplasticizers create many cement mortar bubbles (PCE-1). Calcium ions stabilize polymer bubbles. Aqueous epoxy resin is added to cement slurries to reduce plastic viscosity and boost heat conductivity to make high-porosity cement foams (HPCF). Foamed cement bubble stability is highest at particle wetting angle π/2. SDS in silica suspension adjusts this angle. Ti-extraction blast furnace slag (TEBFS) foam with 20–40% sulfoaluminate cement (SAC) makes foamed cement.

Compressive Strength and Modulus of Poly (dimethylsiloxane)-Hollow Glass Microballoons Syntactic foams reinforced with Nanoclay

Compressive Strength and Modulus of Poly (dimethylsiloxane)-Hollow Glass Microballoons Syntactic foams reinforced with Nanoclay

Compressive Properties of Poly (Dimethylsiloxane)–Hollow Glass Microballoons Syntactic Foams

Polymer syntactic foams are lightweight polymer composites that are prepared by introducing hollow microspheres in a resin. The main endeavour is to obtain a significant reduction in the weight of the composite along with energy absorption. The present investigation aims to prepare poly (dimethylsiloxane) (PDMS)-hollow glass microballoons (HGM) (40–60% v/v) syntactic foams. Not only did HGM reduce the density of the syntactic foams but also act as a reinforcing phase and increase the compressive properties of PDMS. A ∼25% reduction in density was obtained in syntactic foam when compared to the neat elastomer. Similarly, an improvement of ∼118% in compressive strength was attained at 40% loading of HGM in PDMS. Specific compressive strength and toughness values also registered improvements of the order of ∼191 and ∼240% respectively which highlight the potential of PDMS syntactic foams in varied applications.

Cement - Hollow Glass Microballoons Syntactic Foams: Preparation and Compressive Properties

The present study focuses on the preparation of cement-hollow glass microballoons (40–60 % v/v) syntactic foams for construction applications. Conventional rigid fillers like mortar and aggregates enhance the compressive properties but poses heavy load on the buildings and structures. The use of hollow glass microballoons (K46) with a density of 0.46 g cm−3, as filler in cement binder, offers higher compressive strength at comparable densities. Moreover, the compressive toughness and specific compressive toughness values at 40 percent loadings of K46 are found to enhance by ∼ 87 percent and ∼ 157 percent respectively when compared to neat cement. The use of hollow glass microballoons as a filler material is expected to open new possibilities for the construction industry.