Addition Of Fillers Research Articles

The Effect of Rice Husk on the Variability of Physical and Mechanical Properties of Composites

Abstract Rice husk (RH) is one of the most commonly grown and consumed cereals in the world. Because of its low nutritional value, it is not commonly used as a food or fertilizer. Instead, it is often burned or landfilled. To develop RH-based composites for thermal and acoustic nonstructural applications, a balance between achieving satisfactory performance in physical and mechanical properties is essential as well as ensuring reliability and predictability in the behavior of the composites. The inclusion of RH in composites can result in increased variability in their performance because of the husk’s elastic behavior during compaction and its hydrophilic properties. The RH used in the study was collected from Baixo Mondego, Portugal, and approximately 90 % of the particles had sizes ranging from 1 to 4 mm. To reduce cement usage, different mixtures were produced and categorized based on the use of two types of cement, varying percentages of limestone filler, and different quantities of RH. Robust descriptive and inferential statistics (Student’s t-test and Mann–Whitney U test) were employed to analyze the variability of physical and mechanical properties in 10 different RH-based composites. A study was conducted to assess whether a specific mixture formula within a given group exhibited consistent behavior across different batches or yielded intrinsically different results. This helps to identify the key adaptations required in the industrial process of incorporating this biomaterial into composites. The results have shown that it is possible to produce RH-based composites with less variability of performance and potential for nonstructural applications. In this case, cement CEMI/A-L 42.5 R type with limestone filler addition and paste-to-RH ratio by volume between 1.54 and 2.22 was the most sustainable mix design because it had a small variability of results and reduced the cement content.

Separable alginate gel spheres encapsulated with La-Fe modified biochar for efficient adsorption of Sb(III) with high capacity

Sb and its compounds have been widely used in various industrial applications. Therefore, the preparation of Sb adsorbents with easy recovery and excellent adsorption levels is an urgent problem that must be resolved. By calcining and treating La/Fe metal–organic frameworks (MOF) biochar as a precursor, a loaded La-Fe-modified water hyacinth biochar was synthesised and used as a filler to synthesise iron alginate composite gel spheres, MBC/algFe. Through a series of static adsorption experiments, the effects of different filler addition ratios, solution pH, reaction time, coexisting ions, and other factors on the adsorption of Sb(III) were investigated. According to the Langmuir model, the maximum adsorption capacity of MBC/algFe at 25 ℃ was 277.8 mg·g−1. The adsorption mechanism mainly involved hydrogen bonding and metal-organic complexation interactions.

Mechanical Properties and Liquid Absorption of Calcium Phosphate Composite Cements.

Calcium phosphate cements present increased biocompatibility due to their chemical composition being similar to that of the hydroxyapatite in the hard tissues of the living body. It has certain limitations due to its poor mechanical properties, such as low tensile strength and increased brittleness. Thus, the optimal way to improve properties is through the design of novel composite cements. The purpose was fulfilled using a 25% hydroxyethyl methacrylate (HEMA) mixed with 3% urethane dimethacrzlate (UDMA) base matrix with various ratios of polyethylene glycol (PEG 400) and polycaprolactone (PCL). Mineral filler is based on tricalcium phosphate (TCP) with different chitosan ratio used as bio-response enhancer additive. Four mixtures were prepared: S0-unfilled polymer matrix; S1 with 50% TCP filler; S2 with 50% chitosan + TCP filler; and S3 with 17.5% chitosan + TCP mixed with 17.5% nano hydroxyapatite (HA). The mechanical properties testing revealed that the best compressive strength was obtained by S2, followed by S3, and the worst value was obtained for the unfilled matrix. The same tendency was observed for tensile and flexural strength. These results show that the novel filler system increases the mechanical resistance of the TCP composite cements. Liquid exposure investigation reveals a relative constant solubility of the used filler systems during 21 days of exposure: the most soluble fillers being S3 and S2 revealing that the additivated TCP is more soluble than without additives ones. Thus, the filler embedding mode into the polymer matrix plays a key role in the liquid absorption. It was observed that additive filler enhances the hydrophobicity of UDMA monomer, with the matrix resulting in the lowest liquid absorption values, while the non-additivated samples are more absorbent due to the prevalence of hydrolytic aliphatic groups within PEG 400. The higher liquid absorption was obtained on the first day of immersion, and it progressively decreased with exposure time due to the relative swelling of the surface microstructural features. The obtained results are confirmed by the microstructural changes monitored by SEM microscopy. S3 and S2 present a very uniform and compact filler distribution, while S1 presents local clustering of the TCP powder at the contact with the polymer matrix. The liquid exposure revealed significant pore formation in S0 and S1 samples, while S3 and S2 proved to be more resistant against superficial erosion, proving the best resistance against liquid penetration.

Investigating the role of synthesized reduced graphene oxide and graphite micro-fillers on mechanical and fretting wear performance of glass fiber epoxy-based composite

In the current study, graphite was exfoliated using a Hummer’s technique to produce graphene oxide (GO), which was then reduced with hydrazine hydrate (a reducing agent) to produce reduced graphene oxide (rGO) with high purity. The XRD, FT-IR, SEM, and TGA analysis confirmed the synthesis of rGO by stating its crystal phase, chemical functional group, morphology, and thermal stability. The objective of this study is twofold: firstly, to synthesize the reduced graphene oxide (rGO) cost-effectively, and secondly, to explore its potential as an additional filler in Glass Fiber Reinforced Polymer (GFRP) composites. Aiming to enhance their overall performance. The GFRP laminate composite was fabricated through the hand layup technique by varying the concentration of Gr (i.e., 0.5 wt% & 1 wt%) and rGO (i.e., 0.5 wt% & 1 wt%). The morphological study of the fracture surface revealed a proper dispersion of filler obtained at 0.5 wt% and by increasing the concentration to 1 wt% it reveals a clustering of fillers and formation of micro-voids. The result revealed that maximum improvement has been observed in the GFRP composite having 0.5 wt% rGO composite than neat GFRP composite. Incorporation of rGO micro-filler in GFRP laminate composite significantly improved the tensile strength, flexural strength, and in their modulus by 59.56%, 18.21%, 24.45%, and 22.75% respectively compared to neat GFRP laminate composite. In the case of 0.5 wt% graphite filler demonstrates an enhancement in tensile strength, flexural strength, and their modulus by 37.98%, ∼8%, 6.64%, and ∼5% respectively. In fretting wear test reveals that 1 wt% of graphite filler has better wear resistance than all other composites. The worn morphology revealed adhesive and abrasive wear as the predominant wear mechanism. The incorporation of rGO filler in GFRP makes it a promising material for industrial applications that demand high strength and superior wear resistance.

Utilization of Lignin and Lignosulfonate from Oil Palm Empty Fruit Bunches as Filler in PVDF Proton Exchange Membrane Fuel Cell

A study on the polyvinylidene fluoride (PVDF) membrane using lignin and lignosulfonate oil palm empty fruit bunch (OPEFB) fillers have been carried out. This study aims to determine the additional effect of lignin and lignosulfonate on PVDF membrane. Lignin sulfonation has a good result proven by Fourier transform infrared spectra with a peak at 1192 cm−1 which indicates sulfonate group. The sulfonation degree was increased by 8.9% for lignosulfonate. The membrane was prepared by the phase inversion method. Data present that all the membranes have an asymmetric structure with finger-like and sponge-like pores. Good thermal stability indicated by thermal gravimetric analysis showed degradation at 432 °C. The mechanical properties of the membrane decrease with the addition of filler. From the X-ray diffraction, peaks appeared at 18.39°, 21.35°, and 23.75° for all the membranes indicating of α and β phases. Lignin and lignosulfonate increased membrane hydrophilicity and water uptake. The presence of the sulfonate group increases the ionic exchange capacity and ionic conductivity up to 2.78 mmol/g and 9.95 × 10−5 S/cm, respectively, for 5% lignosulfonate addition. Thus, PVDF/lignosulfonate has the potential as a polymer electrolyte membrane.

Material Extrusion 3D Printing of PEEK-Based Composites.

High-performance thermoplastics like polyetheretherketone (PEEK), with their outstanding thermal stability, mechanical properties and chemical stability, have great potential for various structural applications. Combining with additive manufacturing methods extends further PEEK usage, e.g., as a mold insert material in polymer melt processing like injection molding. Mold inserts must possess a certain mechanical stability, a low surface roughness as well as a good thermal conductivity for the temperature control during the molding process. With this in mind, the commercially available high-performance thermoplastic PEEK was doped with small amounts of carbon nanotubes (CNT, 6 wt%) and copper particles (10 wt%) targeting enhanced thermomechanical properties and a higher thermal conductivity. The composites were realized by a commercial combined compounder and filament maker for the usage in a material extrusion (MEX)-based 3D-printer following the fused filament fabrication (FFF) principle. Commercial filaments made from PEEK and carbon fiber reinforced PEEK were used as reference systems. The impact of the filler and the MEX printing conditions like printing temperature, printing speed and infill orientation on the PEEK properties were characterized comprehensively by tensile testing, fracture imaging and surface roughness measurements. In addition, the thermal conductivity was determined by the laser-flash method in combination with differential scanning calorimetry and Archimedes density measurement. The addition of fillers did not alter the measured tensile strength in comparison to pure PEEK significantly. The fracture images showed a good printing quality without the MEX-typical voids between and within the deposited layers. Higher printing temperatures caused a reduction of the surface roughness and, in some cases, an enhanced ductile behavior. The thermal conductivity could be increased by the addition of the CNTs. Following the given results, the most critical process step is the compounding procedure, because for a reliable process-parameter-property relationship, a homogeneous particle distribution in the polymer matrix yielding a reliable filament quality is essential.

Interfacial interaction behavior of recycled asphalt pavement: Molecular dynamics simulation

Recycling waste asphalt mixture (WAM) to prepare recycled asphalt pavement (RAP) is an important measure to handle road construction waste. Asphalt-aggregate interface (AAI) and matrix-aged asphalt interface (MAI), as weak interfaces in RAP, interface interaction behavior directly affects the road performance of RAP. In this paper, molecular models of asphalt and aggregate were constructed. Molecular dynamics simulation was used to analyze and evaluate the interaction behavior of the AAI and the MAI in RAP. The mean square displacement (MSD), relative concentration function (RCP), and radial distribution function (RDF) were used to quantitatively analyse the interface interaction behavior. The research results are as follows: For the AAI, the temperature, the aging level of asphalt, and chemical composition of aggregates will affect the interaction behavior of the AAI. Increasing temperature accelerates the diffusion of asphalt on the surface of aggregate. However, the increase of the aging level of asphalt and the alkalinity of aggregate will decrease the interaction rate of asphalt on the surface of aggregate. For the MAI, the temperature and the ratio of filler-asphalt (RFA) significantly affect the interaction behavior of the MAI. The molecular diffusion rate of matrix asphalt and aged asphalt increases significantly with the increasing temperature. The addition of filler will decrease the diffusion rate of asphalt, and the diffusion rate decreases with the increase of RFA. This article comprehensively and systematically studies and evaluates the effect of various factors on the interface interaction behavior. The results provide guidance for improving the adhesion ability of AAI and enhancing the degree of incorporation of MAI.

Different aspects of polymer films based on low‐density polyethylene using graphene as filler

AbstractThe focus of the present work is to prepare low‐density polyethylene (LDPE)‐graphene (G) nanocomposite films with improved gas barrier properties by melt extrusion. A narrow range of the graphene (0.05–0.3 wt.%) as filler was used in the LDPE matrix. The rheological analysis indicating that there is no significant influence on the LDPE chains mobility with the addition of filler. The nanocomposites percent crystallinity (Xc%) increase from 25.0% to 31.6% compared to neat LDPE. The X‐ray diffractogram shows a change in width half height of the peak positioned at 26° ((002) plane) from 0.69 (graphite) to 1.24 (graphene), revealing the asymmetry of this plane. The optical microscopy images show a good dispersion of the nanoparticles in the polymer matrix. The mechanical properties of the nanocomposites in longitudinal direction demonstrate better improvement with addition of the filler as compared to the transverse direction. The contact angle measurements of nanocomposites for water and ethylene glycol do not shows a significant variation in comparison to neat LDPE. The nanocomposites show 26% enhancement in the oxygen barrier property. Thus, here we present the cost‐effective LDPE‐graphene nanocomposites with improve oxygen barrier property, which can be used in different industrial application especially in food packaging.

Microbial driving mechanism for nitrogen removal performance of anammox with combined fillers addition: Microbial community dynamics, metabolic function and network analysis

Microbial community is vital for efficient nitrogen removal in an anaerobic ammonium oxidation (anammox) system. However, the mechanisms of microbially driven anammox denitrification are far from clear. The results showed that the nitrogen removal efficiency (especially the removal rate of NH4+-N, which reached 85.6 ± 3.1 %) significantly increased (p < 0.05) by combined fillers addition. Scanning electron microscope (SEM) images showed the microflora changed gradually from short rod-shaped to spherical aggregates, improving shock loading resistance in the system. The dominant microflora shifted from Proteobacteria and Bacteroidetes to Chloroflexi and Planctomycetes, in which Candidatus Jettenia reached a maximum abundance of 30.7 %. Meanwhile, the abundance of denitrifying bacteria (Denitratisoma and Thiobacillus) was significantly diminished. Significant enhancements in the energy metabolic capacity of microorganisms, especially nitrogen metabolism, were observed in the anammox process. Moreover, the increase in abundance of hzo gene suggested the enhancement of the anammox process. Co-occurrence network analysis demonstrated that the genera Longilinea, Thiobacillus, Candidatus Jettenia, Dokdonella, and Candidatus Brocadia were the keystones, and complex microbial interactions (stronger symbiotic than competitive relationships) enhanced the nitrogen removal capability. Overall, the results of this study provided more comprehensive information regarding community succession, coexistence and collaboration in anammox process for nitrogen removal.

Advanced properties and failure characteristics of hybrid GFRP-matrix thin laminates modified by micro glass powder filler for hard structure applications

Fiber reinforced polymer has been used in a broad scope of engineering equipment due to its outstanding advantages. This study investigated the effect of glass powder filler in the matrix modification of glass fiber reinforced polymer that can be further applied for hard structures. The composites were manufactured using a vacuum-assisted resin infusion method with 0, 2,5, 5, and 7,5 wt percentages of glass powder filler. The results have shown that adding glass powder filler in glass fiber reinforced polymer modifies the physical characteristics and enhances the mechanical properties compared to the neat composite. The failure mechanism obtained from the fracture surface investigation demonstrates bridging mechanisms formed effect of glass powder filler addition in the glass fiber reinforced polymer. The strengthening mechanism is formed to enhance the interfacial bonding between the fiber and the matrix. The results reveal the optimum filler addition percentage at 2,5 wt%. Adding 2,5 wt% glass powder filler enhances the flexural strength and interlaminar shear strength by 18,86% and 19,54%, respectively. The glass powder addition offers higher resistance to interlaminar damage. Additional glass powder with a higher weight percentage above the threshold induced microvoid and agglomeration phenomenon.

Synergistic effect of compatibilized nanoclay/polyethylene fibers on the impact strength of epoxy‐glass fiber nanocomposites

AbstractEpoxy‐based glass fiber nanocomposites (EGFCs) have good static mechanical properties but lack in impact strength. Addition of thermoplastic fillers to EGFCs enhanced the impact strength but with lowered static properties. To overcome this issue, compatibilized polyethylene (PE) fibers and silanized clay platelets were reinforced in the EGFCs. The unique properties of PE fibers such as good toughness, high strength, resistance to chemicals, and light‐weight made them an ideal choice for this purpose. EGFCs were processed through vacuum‐assisted resin infusion molding (VARIM) technique and resulted in significant improvements in an impact strength. Compatibilization of nanoclay/PE fibers was confirmed using FTIR and SEM‐EDS analysis. Nanoclay morphology in EGFCs was determined using XRD and TEM analysis. Reinforcement of maleic anhydride grafted PE fibers and silanized nanoclay in EGFCs significantly increased the impact strength by160% over the reference EGFC (without nanoclay/PE fibers). FE‐SEM micrographs showed improved interfacial interaction among various constituents of EGFCs resulting in superior mechanical performance. The newly developed EGFCs have myriad applications in various industries, namely, automotive (bumpers, frames for racing bicycles etc.), marine (hulls, decks, etc.), aviation (radome, stabilizers, etc.), and sports (archery bows, vault poles, etc.).Highlights Multi‐scale filler‐reinforced EGFCs fabricated through VARIM process. Compatibilized reinforcement significantly improved impact strength. Silanization of nanoclay validated with FTIR &amp; morphology with XRD/TEM technique. SEM‐EDS and FTIR confirmed successful compatibilization of PE fibers. SEM showed improved interfacial interaction among various constituents of EGFCs.

Potential contribution of steel slag fillers to asphalt mastic in terms of microwave heating efficiency, electromagnetic mechanisms and fatigue durability

ABSTRACT This paper investigates the potential contribution mechanisms of steel slag fillers in asphalt mastic, covering asphalt-filler interaction mechanisms, microwave heating efficiency, electromagnetic absorption mechanisms, and fatigue durability. The physico-chemical microscopic mechanisms of the steel slag filler, the limestone filler and the interactions between the fillers and the styrene-butadiene-styrene (SBS)-modified binders were characterized. The microwave-heating efficiency of steel slag-based asphalt mastic (SBS-SS) and limestone-based asphalt mastic (SBS-LS) was quantified. The dielectric behaviour of the fillers and the corresponding mastic was further characterized to reveal the electromagnetic mechanisms associated with the microwave heating technology. The stiffness evolution and the fatigue durability of SBS-based bitumen under the effectiveness of steel slag and limestone fillers were assessed by the viscoelastic continuum damage theory model and dissipative energy approaches. The steel slag fillers exhibited a greater potential to promote microwave heat efficiency than the natural stone fillers due to higher ferric oxide compositions. SBS-SS mastics have an overall greater dielectric constant and loss factor than those of SBS-LS mastics, resulting in superior electric field energy storage and conversion capabilities. The addition of steel slag fillers magnifies the load sensitivity of the bitumen and weakens the fatigue impedance and fatigue life of asphalt mastic composites.

Dynamic mechanical analysis for assessment of carbon fillers in glass fiber epoxy composites

AbstractThe effect of incorporation of micron sized aluminum trihydrate, multi‐walled carbon nanotubes, and graphene nano platelets into glass fiber reinforced epoxy matrix is investigated using dynamic mechanical analysis. The objective of the investigation was to develop polymer central core of high temperature low sag transmission conductor. The effect of individual and hybrid carbon fillers on the viscoelastic properties of the epoxy composites is investigated and discussed. The storage modulus of the glass reinforced epoxy increases by 20% at room temperature due to incorporation of carbon nanofillers. In glass transition region, the increase is higher between 40% and 60% and it varies up to 90% in the rubbery region. Key attributes of carbon filler addition are limited enhancement of storage modulus at room temperature, higher enhancement over glassy, glass transition, and rubbery regions. The carbon fillers extend the temperature range of the glassy region. The cross‐link density, filler efficiency, and degree of entanglement of fibers are estimated to understand the implications of the carbon fillers on the viscoelastic properties. The loss modulus peak of glass epoxy composite increases from 2800 to 3900 MPa with carbon fillers and the increase in glass transition temperature is 47°C. Incorporation of carbon fillers leads to increase of damping factor peak from 0.2 to 0.28. Cole–Cole plots have established the inherent heterogeneity of epoxy systems due to the presence of carbon fillers. Prediction models for storage modulus and damping factor have been proposed to highlight the influence of geometry and size of carbon filler.

Investigating the thermal and mechanical properties of novel LDPE/TiO2 and LDPE/TiO2/CNT composites for 3D printing applications.

The development of new materials is essential for advancing technology and improving the quality of life. With new materials, we can create products that are stronger, more durable, and more efficient. The ongoing research and development of new materials for 3D printing applications continue to drive innovation in various fields, leading to improved products and processes with great benefits. The main goal of this work was to produce a functional filament with a 1.75-mm diameter that may be used for 3D printing. Composite materials were prepared using a low-density polyethylene (LDPE) resin as polymer matrix, and titanium dioxide (TiO2) and carbon nanotubes (CNT) as fillers in various ratios. Up to 15 wt% of TiO2 and 0.25 wt% of CNT were added. Some of the greatest difficulties with high filler content composites are achieving good homogeneity, and in the case of the 3D printing, greatest difficulties are producing the filament with a specific and stable filament diameter. During the 3D printing itself, the fillers can also often cause the nozzle clogging. This paper reports findings of thermal and mechanical properties of the LDPE/TiO2/CNT composites which are significant for the 3D printing process and the applicability of the composite materials. All of the planed composite materials are successfully prepared and 3D printed into the tensile test specimens. The melting point shift caused by the addition of fillers did not show consistent pattern at differential scanning calorimetry, as all of the samples had melting temperatures around 113.5 ± 1.4 °C. The addition of filler, according to the TGA, increased the threshold temperature for the material decomposition, in case of TiO2 5.4 °C increase, while TiO2 and CNT combination increased the threshold temperature for 6.8 °C. The results of the tensile test show a general increase trend with addition of TiO2 filler but do not show to a trend for the tensile strength as a result of the addition of CNT filler. The sample with highest TiO2 filler ratio of 15% (LDPE 15T0C) showed the greatest tensile strength of 14.5 MPa, compared to the 13.0 MPa of pure LDPE. The sample with 5% of TiO2 filler and 0.1% of CNT filler (LDPE 5T0.1C) showed the greatest elongation of 73.9%, compared to the 68.9% of pure LDPE.

Investigation of mechanical properties of aluminum–glass fiber-reinforced polyester composite joints bonded with structural epoxy adhesives reinforced with silicon dioxide and graphene oxide particles

In this work, to investigate the mechanical properties of aluminum–glass fiber-reinforced polyester composite joints bonded with structural epoxy adhesives reinforced with silicon dioxide (SD) and graphene oxide (GO) particles, firstly, SD and GO particles were added to epoxy adhesive in varied weight percentages. After the surface treatment made by sanding aluminum and composite sheets with abrasive sandpaper, aluminum sheets and glass fiber-reinforced polyester composite sheets were bonded. Adhesives containing 0.2% SD and 0.25% GO had tensile strengths that were approximately 15.89% and 14.03% greater than neat epoxy, respectively. The lap shear strength of neat epoxy was improved with the addition of filler in all samples, and 0.2% SD and 0.25% GO-reinforced adhesives increased the shear strength of the neat epoxy by 66.57% and 125%, respectively. The adhesion, thin-layer cohesive and light-fiber tear were noted, as well as cohesive and fiber-tear failures based on the damaged surfaces of the samples.

Modified polymer electrolyte membrane for microbial fuel cell: Performance analysis, investigation on anti-biofouling effect, and microbial community analysis on biofouled membrane

Sulphonation is limited in Sulphonated Polyether Ether Ketone (SPEEK) due to its solubility in water beyond an extent. However, to enhance performance of polymer electrolyte membrane (PEM) in microbial fuel cell (MFC), more functional groups are required. To facilitate effective proton transfer, styrene sulphonic acid (SSA) is grafted onto SPEEK, resulting in SPEEK/SSA, to increase the number of functional groups. Based on membrane properties, 5 wt% SSA is found to be the optimum grafting for further filler addition. Copper oxide doped reduced graphene oxide (CuO@rGO) is used as membrane filler at various concentrations to enhance anti-biofouling effect. Swelling is excessive in SPEEK/SSA (30.2%), whereas it is only 17.3% in SPEEK/SSA+1.5 wt%CuO@rGO. As evidenced by the zone of inhibition assay, biofilm inhibition test, and Bradford protein assay, the membrane's anti-biofouling impact is improved by the inherent hydrophilicity of SPEEK/SSA and antibacterial activity of CuO@rGO. The MFC with 1.5 wt% CuO@rGO membrane shows highest maximum power density of 186 ± 5 mW m−2 and Chemical Oxygen Demand removal of 81.23%. Phylogenetic analysis on biofouled membrane shows the predominance of Pseudomonas, Acidovorax and Flavobacterium. The research demonstrates that despite biofouling, the synthesized grafted PEM exhibits high resistance to it and hence performs better.

Investigation of expandable fillers for reversible adhesive bonding in photovoltaic modules

Photovoltaic (PV) is a sustainable energy source and an efficient tool towards CO2 neutrality. However, recycling of PV modules remains challenging due to the strong connection of the multi-material assembly. The present work aims at the development of disbonding concepts for adhesive connections used in PV modules to enable improved recyclability and repairability of such modules. To achieve stimuli-responsive adhesive connections, thermally expandable fillers were implemented in a condensation-curing alkoxy-based silicone adhesive. 10–50 wt% of expandable graphite (EG) as well as 10–50 wt% of thermally expandable microspheres (TEM) were incorporated to obtain a controlled expansion of the adhesive at elevated temperature. The expansion ratio in dependence on time and temperature was examined. Furthermore, nanoscale magnetite (Fe3O4) passivated with a layer of SiO2 was added to the formulation to trigger the expansion of TEMs, and therefore separation of adhesive bonds by inductive heating. In this approach an efficient heating and expansion of the adhesive layers was feasible by applying an external alternating magnetic field with a ring coil. Aging stability, influence of filler content and expansion of the adhesive layers were further evaluated in lap shear tests. The addition of functional fillers decreased the bond strength by approximately 50% for adhesive layers containing 50 wt% EG. In contrast, adhesives with 50 wt% TEM exhibited a higher bond strength (by 10%) compared to the unfilled silicone system. Thermally triggered expansion significantly lowered the bond strength (20–30%) for TEM-filled adhesives and led to separation for EG-filled adhesives. Temperature cycling tests had no influence on the filled and unfilled adhesive's strength, whereas after damp heat tests all samples exhibited a lower (less than 40% of the unaged, pristine reference samples) but similar bond strength.

Thermo‐mechanical property enhancement of rigid polyurethane foam using silica and alumina as hybrid fillers over single filler

AbstractSilica and alumina particles were loaded in the rigid polyurethane foam composite as hybrid fillers. After the successful addition of silica and alumina as fillers, various properties of the foam composite were enhanced up to a particular weight percentage (7.5 wt% of silica and alumina each) with respect to alumina loaded foams. Hard urea domains are well distributed in the urethane matrix which indicates the absence of the peak representing H‐bonded urea in the Fourier‐transform infrared spectroscopy results. The addition of hybrid fillers into the rigid polyurethane foam matrix improved the compressive strength of the foam composite by 14% in comparison to alumina loaded foams due to the synergistic effect of the hybrid fillers. The foam composite at 7.5 wt% loading of hybrid fillers was successful in decreasing the thermal conductivity by 9% with respect to the thermal conductivity of the unloaded foam. There was a reduction in the gross calorific value up to 7% in the hybrid filler loaded foam composite when compared with that of the alumina loaded composite. Hence, hybrid fillers should be added to enhance the composite's properties by a greater extent.Highlights From the compressive test results, an increase in the compressive strength up to 14% was observed in the samples loaded with hybrid fillers with respect to the samples loaded with alumina due to the synergistic effects of the two fillers. For the foam composite loaded with alumina, the gross calorific value decreased up to 6% when compared to the unloaded foam. The gross calorific value decreased by a further 7% when hybrid fillers were added to the polyurethane foam composite with respect to the alumina loaded foam composite. The foam composite loaded with 7.5 weight % of hybrid fillers had lower values of thermal conductivity when compared with that of the unloaded polyurethane foam. We propose the addition of both alumina and silica as hybrid filler particles as they enhanced the various properties of the polyurethane foam composite to a greater extent than the addition of alumina particles as a single filler and have potential to replace unloaded polyurethane foams in different applications.

Mechanical behavior of basalt-reinforced epoxy composites modified with biomass-derived seashell powder

The effect of resin modification through the incorporation of the biomass waste in the form of seashell powder on the mechanical properties of basalt fiber–reinforced epoxy/seashell composites is examined through experimental investigations. The resin modification is done through the addition of seashell powder in 5, 10, 15, and 20 wt.%. The modified resin is then reinforced with basalt fiber mat and the required laminate is obtained through compression molding technique. The specimens required for various mechanical tests, such as flexural, tensile, inter laminar shear (ILSS), and the impact strengths, are cut from the laminate as per the standard ASTM dimensions. The mechanical test results indicate that through the addition of the seashell filler additional toughening mechanisms are introduced which improves the strength of the composite laminate. The improvement in the flexural modulus value for all the laminates made from modified resin indicates the ability of the laminate to deflect the applied load effectively and efficiently. The optimum wt.% addition of seashell filler into the resin is found to be 5% for flexural, ILSS, and impact strength while for tensile strength it was observed to be 10%. The addition of higher wt.% loading of seashell filler into the resin has rendered the resin too thick and viscous with minimum flowability. Thus, there is a reduced wettability of the modified resin with the basalt fibers due to which the strength of the laminates reduces. The SEM analysis indicates widespread delamination for higher wt.% addition of the seashell filler into the resin.

Structural, thermal, and mechanical characterisation of PEEK-based composites in cryogenic temperature

Thermal, thermo-mechanical and mechanical properties of four different commercially available polyetheretherketones (PEEK) based materials were investigated. PEEK matrix was either modified and/or reinforced with carbon fibres, graphite and/or PTFE. Impact strength was measured at three different temperatures: 25 °C, −100 °C, and −195 °C. At 25 °C, thermal stability and mechanical properties, including the elastic modulus, compression, and impact strength, were enhanced with the addition of carbon fibres. Matrix modification had a minor impact on thermal stability, while the mechanical properties decreased, except for impact strength. At −100 °C, the mechanical properties of the neat polymers were improved, including increased impact strength by 20% compared to values at 25 °C. Addition of fillers hindered the rise of impact strength due to complex mechanisms caused by different coefficients of thermal expansion of reinforcements and matrix. At −195 °C, the significant increase of impact strength was revealed for unmodified PEEK reaching 30 times higher values than at 25 °C, while matrix modification suppressed the rise of impact strength. The scratch test indicated the superior behaviour of unfilled PEEK during the tested load range (up to 15 N), while the effect of the fillers was observed at much lower load threshold of 7 N.