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This study investigates the influence of nano clay reinforcement on the mechanical behavior of Kevlar/epoxy composite laminates and sandwich structures subjected to quasi‐static punch shear loading. Three types of composite face sheets were fabricated using hand lay‐up technique: Kevlar/epoxy neat, 0.5, and 1 wt. % of nano clay. The mechanical properties of these composites were characterized through compression, shear, and tensile tests. Sandwich structures were then constructed using the fabricated face sheets and an aluminum honeycomb core. Quasi‐static punch shear tests were performed on the composite laminates and sandwich specimens using hemispherical impactors. Numerical simulations of the punch shear tests were conducted in LS‐Dyna, employing appropriate material models and contact definitions for the constituent materials. Furthermore, to further investigate the failure mechanisms, scanning electron microscopy (SEM) analysis was conducted on the fractured Kevlar/epoxy composite plate specimens. The comparison between the experimental outcomes and numerical data demonstrated a strong correspondence, indicating consistency between the two methodologies. In conclusion, the incorporation of 0.5 wt. % nano clay into the Kevlar/epoxy composite resulted in a 5.09% increase in shear strength and an 11.29% increase in maximum reaction force. The study provides insights into the effect of nano clay reinforcement on the punch shear resistance and energy absorption capabilities of Kevlar/epoxy composites and sandwich structures. Highlights: Proper alignment of the nano clay within the epoxy was achieved.The most efficient rate of nano clay was observed to be 0.5% by weight.The mechanical properties of nano clay‐containing composites were improved.Quasi‐static punch shear tests were performed numerically and experimentally.Numerical results were in close agreement with experimental results. [ABSTRACT FROM AUTHOR]

Adding heterogeneous fillers with high thermal conductivity (TC) to polymer has been recognized as an effective way to increase the effective thermal conductivity (ETC) of polymer composites. Extensive researches have been conducted on the ETC of composites with heterogeneous fillers. However, the heat transfer enhancement mechanism of heterogeneous fillers remains unknown, and the combined effects of filler size, filler contact, interface thermal resistance (Rc) and other parameters on the ETC have not been explored. In this study, above combined effects are investigated. The results show that the filler contact and Rc are the key factors determining the ETC. The ETC of composite with filler contacts reaches 2.35 at filler content of 25%, which is 11.9% higher than that without filler contacts. The ETC also strongly depends on the R*c (dimensionless form of Rc) ratio (R*c1/R*c2) between two fillers, with it becoming asymmetrical when the amount of R*c(R*c1 + R*c2) is larger. The ETCs decrease with the increase of R*c1/R*c2 when the R*c1/R*c21. When R*c1 + R*c2 is a constant, the ETC increases with the competing effects of R*c. The models with filler contacts exhibit higher accuracy than other classical models in calculating the ETC across the entire range of filler content.

The paper focuses on spatial modelling of composites with discontinuous reinforcement. The algorithm for creating a representative volume element (RVE) must consider random distribution and size of reinforcing particles (RP), prevention of RP interpenetration, and maintaining the desired volume fraction of the reinforcing phase (Vp) in the composite microstructure. Assuming fixed RVE dimensions and randomly determined RP size, the actual Vp value needs to be continuously determined. If the assumed (desired) Vp is lower than the current value, additional reinforcement is added to the RVE. As the RP location is random, some particles may extend beyond the RVE limits, affecting Vp calculation. The research aims to determine the RP volume within the RVE boundaries when RP extends outside. The RVE was discretized with N points, and the number of Ni points within the area occupied by RP was determined. The sought value was calculated using the ratio Ni /N = Vp /VRVE, where VRVE, is the volume of the RVE. Two discretisation methods, systematised (RI) and random (Monte Carlo (MC)), were employed. The study investigated the effects of discretisation type and number N points on calculation accuracy and microstructure generation time for particle-reinforced composites in sphere, cylinder, and ellipsoid shapes. Systematised discretisation yielded higher accuracy/stability, with number N dependent on RP dimensions. The MC method reduced generation time but introduced instability and significant errors. [ABSTRACT FROM AUTHOR]

An advanced shrink–expand–shrink method is proposed in this paper for efficiently modeling concrete-like particle-reinforced composites with ultrahigh volume fraction of aggregates. The gradation of the aggregates can be pre-given and the aggregate spatial distribution can be nonuniform. By this method, the shrunk aggregates are first generated in the model space, and then expanded to jostle each other, afterwards they are shrunk again to normal size to obtain the final mesostructure models. Any high volume fractions of particles even more than 90% can be easily achieved by adjusting the shrinkage level during this process. Besides, a gradient distribution algorithm is established to conform to the aggregate segregation during the actual pouring process, and the corresponding periodic boundaries can also be generated to quickly create large specimens. Finally, the compression processes of polymer concrete with different aggregate packing densities are calculated via a finite element method. The shrink–expand–shrink method and the corresponding numerical models have memorable importance in the performance analysis and material design of particle-reinforced composites. [ABSTRACT FROM AUTHOR]

This study evaluates the influence of joint parameters of extrusion (extrusion profile temperature) and injection molding (barrel profile temperature and mold temperature) manufacturing processes on the mechanical performance of biocomposite materials via the Taguchi and multiple regression techniques. Statistical analysis of variance (ANOVA) was performed to determine the most influential controllable factors for the individual responses. The results of the study revealed that the mechanical properties of the biocomposites are affected by the joint parameters of the two-step manufacturing techniques. This study will help in the process design of biocomposites with improved mechanical performance.

Covalently bonded particles may exhibit extremely high strength, but their performance in the reinforcement of metal alloys crucially depends on the properties of their interfaces with the embedding matrix. Here, density functional theory is used for investigating a range of interface configurations between magnesium and silicon carbide in view of their mechanical properties. Interfaces are analyzed not only in terms of interface energy/work of separation but also in terms of the interfacial shear stresses required to induce interface-parallel displacements. These properties are studied for bilayer systems with different orientations of the Mg and SiC layers and for different terminations of the SiC layer (Si or C atoms located at the interface). The results are discussed in terms of their implication for mechanical behavior of SiC reinforced Mg alloys. [ABSTRACT FROM AUTHOR]

TiCx/Al composites were successfully prepared in this study by dissolving graphite particles in Al-Ti melt based on the principle of a solid–liquid in situ reaction. It was observed that the microstructure of the TiCx/Al composites changed with changes in the reaction temperature and graphite particle size. With an increase in reaction temperature, the TiCx particles in the TiCx/Al composites transitioned from a spider-like distribution to being evenly dispersed in the Al matrix. Additionally, the morphology of the TiCx particles changed from polygons of various sizes to quasi-spherical shapes with a uniform particle size, while the presence of Al4C3 and Al3Ti in the matrix diminished. The size variation of the graphite particles had minimal impact on the particle size and stoichiometric ratio of TiCx generated in the sample. Furthermore, an appropriate graphite particle size was found to mitigate the agglomeration and residue of graphite particles during the in situ reaction. [ABSTRACT FROM AUTHOR]

This study aimed to ascertain the alterations in aging responses of fiber‐reinforced composites, as well as the effects of their natural particle reinforcement, through exposure to acidic and alkaline solutions. Specimens were produced with 0 wt. % (neat), 1 wt. %, 2 wt. % and 3 wt. % particle ratios from acorn and pinecone particles. A particle content of 2 wt. % was determined to yield the best mechanical properties in all mechanical tests conducted for pinecone reinforcement. The highest improvement in strength, observed in 3 wt. % pinecone‐reinforced composites, reached 22.5% at flexural strength. HCl and NaOH diluted in water were chosen as aging solutions. Mechanical tests were repeated at different stages of aging. According to the findings, 1 wt. % particle‐reinforced composites showed better resilience to the mechanical property reduction effect of aging compared to the 2 wt. % and 3 wt. % particle‐reinforced composites. At a particle ratio of 2 wt. %, the acorn‐reinforced specimens exhibit their highest maximum penetration force, which is 5% higher than that of the 0 wt. % composite, consistent with the results of tensile and compressive tests. Highlights: Composite material was manufactured by hand lay‐up and vacuum bagging method.Specimens were aged using acid and base solutions.Tensile, compressive, and bending results were obtained depending on particle type and ratio.Tensile, compressive, and bending strengths of composites were compared according to various aging times. [ABSTRACT FROM AUTHOR]

Using natural materials as reinforcements for polypropylene to alter composite properties and cost is a well-known approach. Often, wood particles are used for that. These give reasonable reinforcement, but are also sought after by other industries, e.g., for energy production, and may also not be available everywhere. Therefore, the aim of this work was to investigate cherry pit particles as an alternative material for polypropylene reinforcement. Cherry pits originate as a by-product from fruit processing and have not been utilized until now as reinforcement. Cherry pit particles were produced by milling the pits, and afterwards composites were produced by compounding and injection molding. Mechanical properties and melt flow were investigated. We found some reinforcement effect, but to a lesser extent than wood particles. The cherry pit particles contain some fatty acid components, which reduce tensile properties and increase the melt flow rate of the composites. For future applications, methods for reducing these fatty acids to improve reinforcement capabilities should be investigated.

Given their substantial neutron capture cross-section, extreme hardness, and high chemical and thermal stability, boron-based materials are widely used as building blocks to protect against highly ionizing radiations such as gamma rays and neutrons. Indeed, uncontrolled nuclear radiation exposure can be highly hazardous to radiation workers and the general public. In this sense, this work presents an extensive study and experimental evaluation of the nuclear shielding features of boron carbide (B4C) based nanocomposite, where bisphenol-A based polybenzoxazine (BA-PBz) was used as matrix. The latter was used for its wide range of interesting properties that overcome some of the shortcomings of conventional phenolic resins. A two-pot synthesis process was adopted for the synthesis of (BA-Bz) monomer. Moreover, the boron carbide nanoparticles were treated with a silane (KH-560) coupling agent in order to improve the intramolecular interactions with the polymeric matrix. The neutron shielding studies were carried out at the Nuclear Research reactor of Algeria NUR. The results showed that the developed boron carbide-based nanocomposite exhibits intriguing shielding performances and good thermal stability. The highest performances were obtained at a B4C concentration of 5. wt %, where the macroscopic cross section was found to be (Σ = 3.3878 cm−1) with a screening ratio of (S = 97.78%). [ABSTRACT FROM AUTHOR]

Covalently bonded particles may exhibit extremely high strength, but their performance in the reinforcement of metal alloys crucially depends on the properties of their interfaces with the embedding matrix. Here, density functional theory is used for investigating a range of interface configurations between magnesium and silicon carbide in view of their mechanical properties. Interfaces are analyzed not only in terms of interface energy/work of separation but also in terms of the interfacial shear stresses required to induce interface-parallel displacements. These properties are studied for bilayer systems with different orientations of the Mg and SiC layers and for different terminations of the SiC layer (Si or C atoms located at the interface). The results are discussed in terms of their implication for mechanical behavior of SiC reinforced Mg alloys.

TiCx/Al composites were successfully prepared in this study by dissolving graphite particles in Al-Ti melt based on the principle of a solid–liquid in situ reaction. It was observed that the microstructure of the TiCx/Al composites changed with changes in the reaction temperature and graphite particle size. With an increase in reaction temperature, the TiCx particles in the TiCx/Al composites transitioned from a spider-like distribution to being evenly dispersed in the Al matrix. Additionally, the morphology of the TiCx particles changed from polygons of various sizes to quasi-spherical shapes with a uniform particle size, while the presence of Al4C3 and Al3Ti in the matrix diminished. The size variation of the graphite particles had minimal impact on the particle size and stoichiometric ratio of TiCx generated in the sample. Furthermore, an appropriate graphite particle size was found to mitigate the agglomeration and residue of graphite particles during the in situ reaction.

The addition of nano- and microfillers to carbon-fiber-reinforced polymers (CFRPs) to improve their static mechanical properties is attracting growing research interest because their introduction does not increase the weight of parts made from CFRPs. However, the current understanding of the high strain rate deformation behaviour of CFRPs containing nanofillers/microfillers is limited. The present study investigated the dynamic impact properties of carbon-fiber-reinforced phenolic composites (CFRPCs) modified with microfillers. The CFRPCs were fabricated using 2D woven carbon fibers, two phenolic resole resins (HRJ-15881 and SP-6877), and two microfillers (colloidal silica and silicon carbide (SiC)). The amount of microfillers incorporated into the CFRPCs varied from 0.0 wt.% to 2.0 wt.%. A split-Hopkinson pressure bar (SHPB), operated at momentums of 15 kg m/s and 28 kg m/s, was used to determine the impact properties of the composites. The evolution of damage in the impacted specimens was studied using optical stereomicroscope and scanning electron microscope. It was found that, at an impact momentum of 15 kg m/s, the impact properties of HRJ-15881-based CFRPCs increased with SiC addition up to 1.5 wt.%, while those of SP-6877-based composites increased only up to 0.5 wt.%. At 28 kg m/s, the impact properties of the composites increased up to 0.5 wt.% SiC addition for both SP-6877 and HRJ-15881 based composites. However, the addition of colloidal silica did not improve the dynamic impact properties of composites based on both phenolic resins at both impact momentums. The improvement in the impact properties of composites made with SiC microfiller can be attributed to improvement in crystallinity offered by the α-SiC type microfiller used in this study. No fracture was observed in specimens impacted at an impact momentum of 15 kg m/s. However, at 28 kg m/s, edge chip-off and cracks extending through the surface were observed at lower microfiller addition (≤1 wt.%), which became more pronounced at higher microfiller loading (≥1.5 wt.%). [ABSTRACT FROM AUTHOR]

Using natural materials as reinforcements for polypropylene to alter composite properties and cost is a well-known approach. Often, wood particles are used for that. These give reasonable reinforcement, but are also sought after by other industries, e.g., for energy production, and may also not be available everywhere. Therefore, the aim of this work was to investigate cherry pit particles as an alternative material for polypropylene reinforcement. Cherry pits originate as a by-product from fruit processing and have not been utilized until now as reinforcement. Cherry pit particles were produced by milling the pits, and afterwards composites were produced by compounding and injection molding. Mechanical properties and melt flow were investigated. We found some reinforcement effect, but to a lesser extent than wood particles. The cherry pit particles contain some fatty acid components, which reduce tensile properties and increase the melt flow rate of the composites. For future applications, methods for reducing these fatty acids to improve reinforcement capabilities should be investigated. [ABSTRACT FROM AUTHOR]

Thermal protection system (TPS) is of great significance to launch hypersonic flight and landing process of hypersonic vehicles, which can effectively shield the hypersonic vehicle from severe aerodynamic heating encountered. Phenolic aerogels play an important role in TPS due to their characteristics of low density, high porosity, and low thermal conductivity. However, phenolic aerogel is easy to be oxidized at elevated temperatures under oxidizing environments, which severely limits its large-scale application as thermal insulation materials in TPS. In this study, a novel TiB2–B4C/carbon (TB/C) aerogel composite was synthesized by introducing TiB2 and B4C particles into phenolic aerogels through quick-gelation and mechanical mixing. The developed aerogel composites were characterized by scanning electron microscopy, Fourier transform infrared, thermal analysis, etc., to evaluate their microstructure, oxidation resistance, and mechanical properties. Experimental evidence showed that TiB2 and B4C particles reacted with the oxygen-containing molecules to form TiO2–B2O3 layer, which effectively improved oxidation resistance and mechanical properties of phenolic aerogel composites.

The mechanical, electrical, and glass transition behaviors (Tg) of polymethylmethacrylate (PMMA)–metal systems have been studied. Considering both the particle size and the metal filler concentration, the electrical conductivity showed a clear dependence on the sample thickness to reach percolation. An increase of up to 400% of strain-to-failure for the 2% v/v of nanometric filler composites in the mechanical test was observed. Tg analysis showed a decrease in the glass transition temperature when the increase of nanometric metallic filler reached the limit of 2% v/v. Over this concentration, the Tg values showed a tendency to reach the original value of the polymeric matrix without conductive filler. For the 20% v/v micrometric filler composites, the strain-to-failure increased up to 58%, but in the Tg analysis of this composite, no relevant changes were observed when the micrometric metallic filler was increased. [ABSTRACT FROM AUTHOR]

To investigate the effect of volume fraction (VF) on the fracture properties of silicon carbide particle-reinforced 6061 Al matrix composites (SiC p /6061Al), we propose a model for calculating the grain size G and establish a boundary effect model (BEM) that incorporates the VF of SiC p. To validate the rationality of the proposed BEM, three-point-bending tests are conducted at three different temperatures on SiC p /6061Al with three distinct VFs of SiC p. The comparisons show that the calculation results of the proposed BEM are highly consistent with those obtained in accordance with American Society for Testing Materials (ASTM) standards. Our findings reveal that both the tensile strength and fracture toughness of SiC p /6061Al decrease with an increase in VF of SiC p , whereas these properties increase with rising temperature. Fracture analysis indicates a mixed fracture mode, encompassing reinforcement fracture, matrix fracture, and interface debonding. This study provides theoretical support and data references for understanding the influence mechanism of VF of SiC p on the fracture properties of SiC p /6061Al, thereby facilitating the design and optimization of these advanced materials. • A novel model for calculating the grain size G of SiC p /6061Al. • BEM considering the volume fraction of SiC p. • Three-point-bending tests at 17 °C, 60 °C and −60 °C. • BEM results are highly consistent with those of the ASTM. • Fracture toughness decrease with the increase of VF of SiC p. [ABSTRACT FROM AUTHOR]

In the domain of photopolymerization-based additive manufacturing (3D vat printing), ceramic photopolymer resins represent a multifaceted composite, predominantly comprising oligomers, ceramic fillers, and photoinitiators. However, the synergy between the ceramic fillers and polymer matrix, along with the stabilization and homogenization of the composite, is facilitated by specific additives, notably surface-active agents, dispersants, and adhesion promoters. Although these additives constitute a minor fraction in terms of volume, their influence on the final properties of the material is substantial. Consequently, their meticulous selection and integration are crucial, subtly guiding the performance and characteristics of the resultant ceramic matrix composites toward enhancement. This review delves into the array of dispersants and coupling agents utilized in the additive manufacturing of ceramic components. It elucidates the interaction mechanisms between these additives and ceramic fillers and examines how these interactions affect the additive manufacturing process. Furthermore, this review investigates the impact of various additives on the rheological behavior of ceramic slurries and their subsequent effects on the post-manufacturing stages, such as debinding and sintering. It also addresses the challenges and prospects in the optimization of dispersants and coupling agents for advanced ceramic additive manufacturing applications. [Display omitted] • Chemical additives significantly influence 3D printed ceramic resin properties. • The synergy between ceramic fillers and the polymer matrix is crucial for composite homogeneity. • Specific dispersants improve particle distribution within the photopolymerization process. • Adhesion promoters enhance the bonding between ceramic particles and the resin matrix. • Optimizing additive selection is key to advancing ceramic additive manufacturing technologies. [ABSTRACT FROM AUTHOR]

The dichotomy between mechanical performance and repairability is a well‐known fact in the self‐healing field. One alternative to overcome this trade‐off is the inclusion of reinforcing fillers. In this research, hybrid reinforced self‐healing styrene‐butadiene rubber (SBR) composites are developed by combining mechano‐chemically modified ground tire rubber (mGTR) with carbon black (CB). The SBR matrix is systematically analyzed by means of dynamic mechanical analysis and broadband dielectric spectroscopy. The SBR composite reinforced with 20 phr mGTR and 20 phr CB maintains the healing efficiency of the unfilled SBR (80%) and improves its tensile strength by 300%, balancing perfectly well both properties. The healing efficiency is determined at different damage levels. The damage at the microscopic scale is easier to recover and does not depend on the presence of fillers, while the recovery at the macroscopic level clearly relies on the addition of filler, with more demanding healing conditions. [ABSTRACT FROM AUTHOR]

In this study, the influence of particle shapes on the elastoplastic response of composite materials is investigated both experimentally and computationally. Flake, spherical, irregular, and rod type glass particles are used as filler in the epoxy matrix material in various mass fractions: 5, 10, 15 %. For each investigated composite material, mechanical properties such as elastic modulus, tensile strength, and tensile fracture strain are determined by experimentally obtained stress-strain curves. Flake and irregular particle types give the maximum and minimum elastic modulus values, respectively. The addition of glass particles has an adverse effect on the tensile strength and tensile fracture strain. The worst filling types in terms of tensile strength and tensile fracture strain are the flake and the irregular ones due to the stress concentrations at the sharp edges and corners present on these filler particles under loading conditions. On the otherhand, for spherical type fillers that have no sharp corners, debonding seem to be the main failure mechanism. Representative volume element (RVE) approach is utilized to determine experimentally identified properties by means of Finite Element Method. In the model, the debonding among particle and matrix components is simulated through the cohesive zone model (CZM). Computational outputs are quite well compliant with experimental results. Experimental results and computational analysis indicate that along with the aspect ratio, some other morpohological characteristics of particles have a marked effect on the mechanical properties of the particle filled composites, such as presence of sharp corners and edges on the particle geometry and surface area to volume ratio of the particles. [ABSTRACT FROM AUTHOR]

In this study, a latent and tacky epoxy resin (EP) modified with siloxane core-shell-particles was developed and investigated. The use of EP as a towpreg matrix for winding of cryogenic composite vessels requires a certain toughness to resist microcracking. First, the mechanical properties at +90 °C, +22 °C, −50 °C and −196 °C were examined, with emphasis on the fracture toughness at cryogenic temperatures. Although the modulus of the resin increased dramatically, the KIC also increased by + 100% at −196 °C. Compression testing revealed that the associated yield point increased up to 500 MPa at −196 °C. The yield point of the modified resins was reduced by almost 10% which leads to easier yielding and enabling toughening mechanisms. Thus, the KIC value clearly is not the primary property that needs to be improved in cryogenics. Second, the radius of the plastic zone around the crack tip (Rp) was calculated. It decreased mathematically from 1.9 μm to 0.4 μm, due to a reduced energy dissipation resulting from a smaller spatial expansion of the plastic deformation zone. Finally, an optimum value of 3% by volume of polydimethylsiloxane was identified, demonstrating an increase of the Rp to 1.8 μm at −196 °C and proving the necessity of combinatorial methods to understand temperature-dependent failure of epoxy matrices.

The addition of nano- and microfillers to carbon-fiber-reinforced polymers (CFRPs) to improve their static mechanical properties is attracting growing research interest because their introduction does not increase the weight of parts made from CFRPs. However, the current understanding of the high strain rate deformation behaviour of CFRPs containing nanofillers/microfillers is limited. The present study investigated the dynamic impact properties of carbon-fiber-reinforced phenolic composites (CFRPCs) modified with microfillers. The CFRPCs were fabricated using 2D woven carbon fibers, two phenolic resole resins (HRJ-15881 and SP-6877), and two microfillers (colloidal silica and silicon carbide (SiC)). The amount of microfillers incorporated into the CFRPCs varied from 0.0 wt.% to 2.0 wt.%. A split-Hopkinson pressure bar (SHPB), operated at momentums of 15 kg m/s and 28 kg m/s, was used to determine the impact properties of the composites. The evolution of damage in the impacted specimens was studied using optical stereomicroscope and scanning electron microscope. It was found that, at an impact momentum of 15 kg m/s, the impact properties of HRJ-15881-based CFRPCs increased with SiC addition up to 1.5 wt.%, while those of SP-6877-based composites increased only up to 0.5 wt.%. At 28 kg m/s, the impact properties of the composites increased up to 0.5 wt.% SiC addition for both SP-6877 and HRJ-15881 based composites. However, the addition of colloidal silica did not improve the dynamic impact properties of composites based on both phenolic resins at both impact momentums. The improvement in the impact properties of composites made with SiC microfiller can be attributed to improvement in crystallinity offered by the α-SiC type microfiller used in this study. No fracture was observed in specimens impacted at an impact momentum of 15 kg m/s. However, at 28 kg m/s, edge chip-off and cracks extending through the surface were observed at lower microfiller addition (≤1 wt.%), which became more pronounced at higher microfiller loading (≥1.5 wt.%).

In this paper, the interfacial adhesion work (Wad), tensile strength, and electronic states of the Fe-amorphous Na2SiO3-Al2O3 and Fe-Al2O3 interfaces are well-investigated, utilizing the first-principles calculations. The results indicate that the Fe-amorphous Na2SiO3-Al2O3 interface is more stable and wettable than the interface of Fe-Al2O3. Specifically, the interfacial adhesion work of the Fe-amorphous Na2SiO3 interface is 434.89 J/m2, which is about forty times that of the Fe-Al2O3 interface, implying that the addition of amorphous Na2SiO3 promotes the dispersion of Al2O3 particle-reinforced. As anticipated, the tensile stress of the Fe-amorphous Na2SiO3-Al2O3 interface is about 46.58 GPa over the entire critical strain range, which is significantly greater than the Fe-Al2O3 interface control group. It could be inferred that the wear resistance of Al2O3 particle-reinforced is improved by adding amorphous Na2SiO3. To explain the electronic origin of this excellent performance, the charge density and density of states are investigated and the results indicate that the O atom in amorphous Na2SiO3 has a bonding action with Fe and Al; the amorphous Na2SiO3 acts as a sustained release. This study provides new ideas for particle-reinforced composites. [ABSTRACT FROM AUTHOR]

In this unique study, the effect of adding core-shell particles (CSPs) on fatigue performance of carbon-fiber reinforced PA6 (CF-PA6) laminates is investigated. The thermoplastic laminates were prepared using compression molding and were reinforced at ply interfaces with 2 wt% and 4 wt% CSPs of the polymer mass. A manual method was used to disperse CSPs using a sieve and carefully selected process parameters. The cyclic tests were conducted and assessed, considering S–N curve, stiffness degradation, and energy dissipation. Consequently, the fatigue life of modified composites improved respectively by eight and four times when 2 wt% and 4 wt% CSPs were used. The results showed that an optimal improvement was achieved with a 2 wt% CSPs. The fatigue strength coefficient and fatigue strength exponent of CF-PA6 composites improved by 22.13 % and 9.85 %, respectively. The findings have the potential to establish a new frontier in thermoplastic research and would help designers to enhance the fatigue properties of thermoplastic laminates in specific elastic tailoring structures. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, high performance styrene-butadiene rubber (SBR)/clay nanocomposites (NCs) modified by cocoamidopropyl betaine (CAPB) are prepared via an efficient and facile strategy. CAPB-modified SBR was compounded with clay gel via gel compounding method to obtain SBR/clay composites. The effect of processing condition and CAPB on the mechanical properties of the SBR/clay composites was investigated. XRD and TEM results show that clay dispersion in SBR matrix is significantly improved due to the success of CAPB in the hydrophilic modification of SBR. The clay-SBR interaction is enhanced and more SBR molecular chains are adsorbed to the clay, significantly improving the mechanical properties of SBR/CAPB/clay NCs, as demonstrated by SEM and DMA. The maximum tensile strength of SBR/CAPB/clay NCs achieved 16.3 MPa at a clay loading of 40 phr, which is 10 times that of pure SBR. The tensile strength of the SBR/CAPB/clay NC incorporated with 20 phr clay has exceeded that of the SBR composite incorporated with 40 phr commercial organic clay. This work demonstrates that this strategy, which combines the CAPB-modification of SBR with the gel compounding method, is an effective and feasible method to improve the mechanical strength of SBR. [Display omitted] [ABSTRACT FROM AUTHOR]

Matrix microcracking is considered the main factor responsible for the gas permeation in linerless pressure vessels and storage tanks. The addition of halloysite nanotubes (HNTs) to them at different concentrations was studied in order to enhance their microcrack resistance. A 50% increase in the cracking onset stress was found at a 5% addition of HNTs to the epoxy matrix. Moreover, a 60% increase was observed at a similar level of microcrack density compared with that of neat epoxy. A reactive diluent was used as an alternative to keep the viscosity suitable for the filament winding process and to offset the rise in viscosity by HNT incorporation. Despite the fact that the matrix fracture toughness increased even to 10% of HNTs, no growth in the microcrack resistance was found at more than 5% of HNTs. As a result, it was concluded that the microcracking phenomenon can be affected not only by the matrix fracture toughness, but also by the residual thermal stresses. [ABSTRACT FROM AUTHOR]

Featured Application: Welding technology. This paper presents modern copper-matrix composite materials in which volcanic tuff particles are used as a reinforcing phase. The aim of the research was to determine the optimal shares of volcanic tuff additive based on such criteria as softening temperature, relative density, electrical conductivity, and hardness. The properties of the produced and tested composites allowed us to determine the usefulness of this type of material for resistance welding electrodes. To confirm the assumptions made, preliminary investigations of the durability and behavior of electrodes made of the tested material during the processes of welding non-alloy steel sheets were carried out. As a result of the research, it was discovered that the addition of 5% tuff produces the best results in this type of composite. It was found that for the sample with a 5% share of tuff, a high softening point above 600 °C was obtained, high hardness after densification at the level of 62 HRB, and high relative density of approximately 95% and very good conductivity at the level of approximately 45 MS/m. The conducted tests did not show any electrode wear different from the commonly used alloys for resistance welding. [ABSTRACT FROM AUTHOR]

By considering the surface free energy effect, an analytical investigation on the fracture behaviors of nanoparticle-reinforced composites was performed in this study. The plastic zones ahead of the crack tips based on the Irwin model were introduced in our analysis, which has a significant influence on the fracture toughness of inelastic structures, especially for polymer and metal matrix composites. Take copper and aluminum nanoparticles as examples, comprehensive parametric studies were conducted to investigate the interaction between a Griffith crack and the nearby nanoparticle. It was found that for nanoparticles with the radius of less than 10 nm, apart from the mechanical property of the nanoparticle, the surface free energy effect plays a dominant role in determining the fracture behaviors of the nanoparticle-reinforced composites. Moreover, taking the surface free energy into account, a decrease in the plastic zone size is obtained, particularly for the crack tip nearer the nanoparticle. [ABSTRACT FROM AUTHOR]

In this paper, the finite element simulation approach for studying the steady-state heat transfer and predicting the effective thermal conductivity of composites has been proposed. 3D representative volume elements considering the polyhedral- and spherical-shaped inclusions are generated. Different meshing approaches for meshing these complex structured composites have been used, and the mesh quality is studied based on mesh metrics: element quality and skewness, and next, a convergence study is conducted to ensure mesh-independent results. Three different boundary conditions: mixed, constant temperature gradient and uniform flux has been used to predict the effective thermal conductivity of composites. The predicted results from simulations are in good agreement with the experimental values reported in the literature. It has been observed that the random orientation and interpenetration of particles lead to a much better heat flow and hence the higher values of effective thermal conductivity of composites. For high volume fraction composites, as the number of particles having interpenetration increases, their effective thermal conductivity increases. For low volume fraction composites, constant temperature gradient boundary condition overpredicts the effective thermal conductivity and for high volume fraction composites, uniform heat flux and mixed boundary conditions predict higher values. A design point study was conducted, considering the ratio of thermal conductivity of constituents, as a design parameter. It has been observed that by reinforcing the high thermal conductivity inclusions as an interpenetrating phase, the effective thermal conductivity of composites can be increased substantially. The reinforcement of very high conductivity material cannot yield the desired ETCs if the reinforced particles are rendered uniformly oriented with no contacts between them. [ABSTRACT FROM AUTHOR]

The growing need for high thermal and mechanical resistant lightweight syntactic foams demands the designing of new materials. Herein, we report the successful fabrication of lightweight and high thermal resistance syntactic foams with excellent thermal and good mechanical properties. For this end, 10–50 wt% hollow glass microsphere (HGMS) containing polybenzoxazine based syntactic foams were prepared by using bisphenol‐A‐aniline (BA‐a) and phenol‐diaminodiphenylmethane (P‐ddm) benzoxazine via curing at 10 MPa compression molding. The curing behavior, tensile, flexural, compressive, and impact strength, thermal properties, and fracture morphology of the syntactic foams were studied by DSC, universal material testing machine, and drop hammer impact testing machine, TGA, and SEM, respectively. The curing temperatures of BA‐a and P‐ddm benzoxazine resins were slightly increased after blending the HGMS. The highest decline (59%) in the density and highest void contains (13.17%) was recorded for the poly(P‐ddm/HGMS50) sample. The excellent specific mechanical properties of the syntactic foams were observed on the 30 wt% HGMS loading. The thermal conductivity of the foams was gradually decreased and the lowest values of 0.106 and 0.0985 W/m.K were observed for poly(BA‐a/HMGS50) and poly(P‐ddm/HGMS50) sample, respectively. Furthermore, a gradual improvement in the thermal properties was observed as the loading of HGMS increased. [ABSTRACT FROM AUTHOR]

The mechanical, electrical, and glass transition behaviors (Tg) of polymethylmethacrylate (PMMA)–metal systems have been studied. Considering both the particle size and the metal filler concentration, the electrical conductivity showed a clear dependence on the sample thickness to reach percolation. An increase of up to 400% of strain-to-failure for the 2% v/v of nanometric filler composites in the mechanical test was observed. Tg analysis showed a decrease in the glass transition temperature when the increase of nanometric metallic filler reached the limit of 2% v/v. Over this concentration, the Tg values showed a tendency to reach the original value of the polymeric matrix without conductive filler. For the 20% v/v micrometric filler composites, the strain-to-failure increased up to 58%, but in the Tg analysis of this composite, no relevant changes were observed when the micrometric metallic filler was increased.

In the current study, 1 wt%, NaOH treated pine cone (ATPC) particles composites with bisphenol‐A aniline based benzoxazine (BA‐a) matrix were prepared by isothermal compression method. Ultimate impacts of ATPC reinforcement on the thermomechanical, tensile, flexural, and impact properties of the composites were studied by using a dynamic mechanical analyzer (DMA), a Universal testing machine, and a Tinius‐Olsen impact device, respectively. The thermal stability of ATPC particles was remarkably increased, TGA confirmed that particles will not be degraded during the curing. The DMA results of 30 wt% ATPC reinforced composites confirmed that the glass transition temperature, storage modulus, and loss modulus were 22°C, 2510, and 250 MPa higher than the neat matrix, respectively. In addition, the impact strength of the 30 wt% ATPC reinforced composites was nearly 3 times higher than the neat matrix, which confirmed that the matrix's brittleness is reduced, similar observation was confirmed by the Brostow and coworkers empirical model. Moreover, a gradual rise in the tensile and flexural properties was also recorded. We can easily conclude from the studied parameters that the ATPC particles can be used as a sustainable agro‐waste in polymeric composites. [ABSTRACT FROM AUTHOR]

This study describes the viscoelastic characterizations of unmodified and heat-modified mangrove particle (MP)-filled high-density polyethylene (HDPE) composites. The untreated (unmodified) and treated (modified) MPs were compounded with HDPE matrix at 10, 20 and 30 wt% in a twin-screw extruder and compression moulded into thin sheets for rheological characterizations (amplitude and frequency sweeps). The amplitude sweeps of the dynamic rheological analysis indicated that 20 wt% treated composite has the highest linear viscoelastic region of 0.1% with the highest storage and loss modulus of 1310 and 150 kPa, respectively. The frequency sweep showed an increase in storage and loss moduli as particle loading increased. The zero shear viscosities of pure HDPE were nearly 3990 Pa·s, while the MP-reinforced HDPE composites were ≥185,440 Pa·s with treated composites exhibiting higher values. [ABSTRACT FROM AUTHOR]

• A constitutive model is proposed for viscoelastic particle-reinforced composites with interphase. • The predictability of the constitutive model promotes greatly the computational material design. • The constitutive model is comprehensively validated based on FE simulations. • The constitutive model is applied to identify the interphase properties. In this paper, a micromechanics-based constitutive model is proposed for linear viscoelastic particle-reinforced composites with interphase based on the theoretical homogenization framework in the time domain that we recently proposed for viscoelastic composites. All the composite's phases (i.e., the matrix, particle and interphase) are considered as linear viscoelastic materials, whose constitutive responses are governed by the general Maxwell model. The interphase with varying viscoelastic property is approximated by the multiple homogenized layers. The constitutive model of the composites is multiplicatively decomposed as two parts: (1) the effective relaxation function characterizes the time-dependent behaviors, and (2) the referred elastic part refers to the long-term responses. The classical composite-sphere model and three-phase model are extended to derive the variables involved in the constitutive model for the bulk and shear behaviors, respectively. The comprehensive numerical simulations, including the effects of the number of interphase layer, interphase thickness, particle content and loading condition, are carried out to validate the proposed constitutive model. The results reveal that the constitutive model can predict well the viscoelastic behaviors of the particle-reinforced composites with interphase. The validated constitutive model is then applied to identify the viscoelastic properties of the interphase by fitting the predictive results and the experimental data of the "overall" composites. The results show the good consistency for the interphase properties between the theoretical identification and the experimental observation. The discussion of the interphase percolation is then carried out, and the findings demonstrate again that the constitutive model can also give good predictions under the percolation situation. [ABSTRACT FROM AUTHOR]

Linear thermo-elasticity equations are derived in this paper for anisotropic, particle-reinforced composite structures at mesoscale. The full set of equations is first derived at microscale where the structure is represented as a three-dimensional body with spherical inclusions of known spatial distribution. Limiting the consideration by infinitesimal strains and assuming that the inclusions are embedded into the body firmly and that there are no any defects at the interface of inclusions, the mesoscale limit of the set of equations is derived as the scale parameter decreases to 0. Convergence of the corresponding solutions is established. Material characteristics at mesoscale are expressed in terms of Dirac distribution corresponding to a structure with point inhomogeneities. It is shown that the effective or macroscale material characteristics evaluated in terms of the mesoscale ones, match the well-known rule of mixtures. A particular case of Ambarcumyan plate with random distribution of spherical inclusions is studied numerically. [ABSTRACT FROM AUTHOR]

This study models erosion in particulate-reinforced polymeric composites exposed to abrasive particle impacts. When abrasive particles are much smaller than reinforcements, both phases erode gradually at different rates and traditional numerical modeling is not feasible because of the large number of impacts required to be simulated. Thus, a novel surface evolution methodology which bypasses explicit impact modeling is introduced. By solving two coupled nonlinear three-dimensional partial differential equations for the matrix and reinforcements, the composite erosion rates can be predicted based on the individual phase erosion rates. For a 447 µm alumina particle-reinforced epoxy composite eroded by a 22 µm SiC abrasive, the predicted and measured erosion rates agreed within ∼1.5% at oblique incidence and ∼10% at perpendicular incidence. • Surface evolution accurately predicts composite erosion rates in gradual erosion. • Oblique impact boosts composite erosion resistance by ∼29% via protruding particles. • Perpendicular impact causes ∼18% more composite erosion from ricochet and ejection. • As ray tracing shows, ricochet at perpendicular impact causes extra matrix erosion. • FE and SPH methods are not suitable for modeling composite gradual erosion. [ABSTRACT FROM AUTHOR]

In this paper, the interfacial adhesion work (Wad), tensile strength, and electronic states of the Fe-amorphous Na2SiO3-Al2O3 and Fe-Al2O3 interfaces are well-investigated, utilizing the first-principles calculations. The results indicate that the Fe-amorphous Na2SiO3-Al2O3 interface is more stable and wettable than the interface of Fe-Al2O3. Specifically, the interfacial adhesion work of the Fe-amorphous Na2SiO3 interface is 434.89 J/m2, which is about forty times that of the Fe-Al2O3 interface, implying that the addition of amorphous Na2SiO3 promotes the dispersion of Al2O3 particle-reinforced. As anticipated, the tensile stress of the Fe-amorphous Na2SiO3-Al2O3 interface is about 46.58 GPa over the entire critical strain range, which is significantly greater than the Fe-Al2O3 interface control group. It could be inferred that the wear resistance of Al2O3 particle-reinforced is improved by adding amorphous Na2SiO3. To explain the electronic origin of this excellent performance, the charge density and density of states are investigated and the results indicate that the O atom in amorphous Na2SiO3 has a bonding action with Fe and Al; the amorphous Na2SiO3 acts as a sustained release. This study provides new ideas for particle-reinforced composites.

This article presents a micromechanics model to investigate matrix damage evolutions of the particle-reinforced composites (PRCs), as well as matrix failures effect on the stiffness degradation. Compared with the finite-element results and experiment data, it is indicated that the developed micromechanics model can be employed to effectively predict the mechanical behaviors of PRCs. The microscopic three-dimensional stress field distribution is investigated on the basis of the stress concentration region to capture the initial damage behavior of the representative volume element. Moreover, the failure criteria of Hill, Tsai-Wu and maximum stress are incorporated into the proposed micromechanics model to investigate the stiffness reduction properties of PRCs subjected to a uniaxial tensile loading. The microstructure near the interface is further refined to slow down the rapid deterioration around stress concentration regions. The results revealed that the stiffness degradation of matrix significantly affects macroscopic mechanical properties of the PRCs. [ABSTRACT FROM AUTHOR]

Micromechanics-based constitutive models offer superior ability to estimate the effective mechanical properties for the composites, which greatly promote the computational efficiency in the multiscale analysis for composite structures. In this work, a thermo-viscoelastic model for particle-reinforced composites is proposed to estimate their thermal–mechanical coupling behaviors in terms of a micromechanics-based homogenization method in the time domain. The matrix and particles of the composites are modeled as "thermo-rheologically complex" viscoelastic materials. The temperature-dependent effective elastic strain energy ratios of particle to composite are proposed to evaluate the contributions of the matrix and particles. The thermo-viscoelastic model for the composites is then formulated by superposing the matrix and particle's contributions. Finite element simulations based on the representative volume element models are employed to validate the constitutive model under various thermal–mechanical coupling loads. The effects of the loading rate, viscous parameter and particle content on the effective thermal–mechanical responses of the composites are also comprehensively discussed. The experimental data from literature are also employed to verify the constitutive model. The findings show that the proposed thermo-viscoelastic model can accurately predict the thermal–mechanical coupling behaviors for the particle-reinforced composites. [ABSTRACT FROM AUTHOR]

In the present work, the thermal degradation kinetics of a phenolic (PF) and lignin particle-reinforced phenolic (LRPF) foam and the lignin used as the reinforcement (LR) were studied. The activation energies of the degradation processes were obtained using a discrete distributed activation energy model (discrete DAEM) and the Vyazovkin model-free kinetic (MFK) method. The discrete DAEM was validated by comparing the predicted values with the data obtained at 8 °C min−1. Heating ramps of 6 and 12 °C min−1 were used to calculate the kinetic parameters through the model. The effect of the reinforcement on the kinetics of the LRPF was studied by comparison with the results obtained for the PF. For reactions with non-zero mass fractions, the activation energies of the PF were in the range between 79.9 and 177.6 kJ mol−1, and the activation energy for the LRPF ranged from 91 to 187 kJ mol−1. For the LR, the activation energy values were in a narrower range than for the foams: 150–187 kJ mol−1. The degradation process of the LRPF was modified due to the use of LR: the range of activation energy for LRPF was between the ranges for the PF and LR. The activation energy dependence on conversion was also calculated using the Vyazovkin method and compared with the DAEM results; no compensation effect for the kinetic parameters was found. [ABSTRACT FROM AUTHOR]

This paper presents modern copper-matrix composite materials in which volcanic tuff particles are used as a reinforcing phase. The aim of the research was to determine the optimal shares of volcanic tuff additive based on such criteria as softening temperature, relative density, electrical conductivity, and hardness. The properties of the produced and tested composites allowed us to determine the usefulness of this type of material for resistance welding electrodes. To confirm the assumptions made, preliminary investigations of the durability and behavior of electrodes made of the tested material during the processes of welding non-alloy steel sheets were carried out. As a result of the research, it was discovered that the addition of 5% tuff produces the best results in this type of composite. It was found that for the sample with a 5% share of tuff, a high softening point above 600 °C was obtained, high hardness after densification at the level of 62 HRB, and high relative density of approximately 95% and very good conductivity at the level of approximately 45 MS/m. The conducted tests did not show any electrode wear different from the commonly used alloys for resistance welding.

Effect of natural filler amount and kind on the morphological, rheological and mechanical properties of acrylonitrile–butadiene–styrene (ABS) terpolymer was studied in current research. The powdered hazelnut and walnut shells were employed as natural filler with ABS to develop hybrid polymer composites. With single natural filler, it was found that the walnut shell flour was usable for enhancing strengths (tensile, flexural and impact) and modulus (tensile and flexural) in comparison to hazelnut. The highest strengths (tensile, impact and flexural) and flexural modulus were achieved with the amount of 5 wt% hazelnut and 15 wt% walnut shell flour among all hybrid composites. Tensile strain, tensile strength, impact strength, flexural strain and flexural strength of ABS decreased with the mixing of 20 wt% hazelnut and with the mixing of 20 wt% walnut shell flour. The addition of hazelnut shell flour filler alone caused a decrement in melt flow index (MFI) value while the incorporation of walnut shell flour filler alone resulted in an increase in MFI value as compared to pure ABS. It was concluded that hazelnut and/or walnut shell flour-filled polymer composites were usable in applications where lower cost was desirable and some decrements in the mechanical properties were acceptable. [ABSTRACT FROM AUTHOR]

Novel hybrid nanofillers consist of carbon nanotubes (CNTs) and graphitic carbon nitride (g‐C3N4) are prepared for the enhanced mechanical properties of epoxy by improving the dispersion of CNTs. 2D planar structure, large surface area, and plentiful of surface reactive groups of g‐C3N4 efficiently resist the microcrack propagation, impede the thermal transfer, and provide chemical bonding with epoxy chains. The well‐dispersed CNTs by anchoring on g‐C3N4 surface promotes the efficient transfers of stress, and supply the stronger mechanical interlocking for interfacial bonding. The significantly enhanced mechanical properties of epoxy containing hybrid nanofillers are based on the synergistic effects between CNTs and g‐C3N4. Compared with neat epoxy, the tensile strength, tensile modulus, and storage modulus of epoxy containing 0.5 wt% hybrid nanofillers (CNTs: g‐C3N4 = 1: 9, w/w) below glass transition temperature (Tg) are increased by 37.65%, 29.36%, and 32.92%, respectively. Meanwhile, the Tg, onset decomposition temperature and char residue are also obviously raised. [ABSTRACT FROM AUTHOR]

Epoxy resin (diglycidyl ether bisphenol-A type) polymer composites with added pristine and fluorinated carbon nanotubes (CNTs) were studied by FTIR, TGA and electron microscopy. The tensile and flexural strengths of these composites were measured. The specific surface value of the fluorinated CNTs was found to be about 2.26 times higher than that of the one containing the pristine CNTs. The fluorination did not affect the thermal stability of the CNTs below 260 °C and did not worsen the thermal stability of the filled composites. The introduction of 0.1 wt% CNTs fluorinated at 150 °C into the polymer matrix resulted in the increase of the tensile strength of the composite to 89.6 ± 4.1 MPa (35% increase when compared to the unfilled composite). The flexural strength of the composite filled with 0.2 wt% CNTs fluorinated at 150 °C was increased to 199.7 ± 4.8 MPa (+58% when compared with the unfilled composite). The pristine CNTs were less effective in improving the tensile and flexural strengths of the composite when compared with the fluorinated CNTs. The introduction of the fluorinated CNTs into the polymer matrix did not influence the thermal stability of the composite. The reinforced composites can be applied in several areas: aviation, automotive, wind turbine propeller blades, for producing yachts and boats, etc. [ABSTRACT FROM AUTHOR]

Recently accumulative roll bonding (ARB) has been used as a novel method to produce particle reinforced metal matrix composites. The accumulative roll bonding as a severe plastic deformation (SPD) rolling procedure aimed at enhancing the mechanical properties of metals and alloys. The process consists in rolling series of overlapped sheets with a thickness reduction ratio (e.g. 50%). In this study, warm accumulative roll bonding (Warm- ARB) process has been used to produce Aluminum Metal Matrix Composite (AMMC: AA1060/-5% Al2O3). AA1060 strips were roll bonded as alternate layers up to 5 rolling passes with 300°C preheating for 5 minutes before each pass. The microstructure and mechanical properties of composites have been studied after different Warm- ARB passes by tensile test, Vickers micro hardness test and scanning electron microscopy (SEM). The results demonstrated that adding alumina particles into AMMCs improves both the strength and tensile toughness of composites. Moreover, the fracture surfaces of samples after the tensile test have been studied during various ARB cycles by scanning electron microscopy (SEM). Also, the results showed that mechanical properties such as tensile strength and average Vickers micro hardness improved with increasing the number of warm ARB cycles. Also, the elongation and tensile toughness of samples dropped in the primary cycles and improved in continuing with increasing the warm ARB cycles. Finally, warm ARB process would allow producing particle reinforced with good mechanical properties.