Toughening Mechanisms Research Articles

Formation mechanism of Al-O intergranular amorphous phase toughened nanoscale ZrB2-ZrC composite coating synthesized by reactive plasma spraying

A new nanostructured ZrB2-ZrC composite coating with ZrB2-ZrC nanoscale eutectic and ZrB2+Amorphous microstructure was synthesized in situ by plasma spraying Zr-B4C-Al composite powder. The thermal analysis, quenching experiments and microstructure characterization were investigated and the formation mechanism of the bimodal in-situ microstructure was revealed. Al contributed to the liquid phase separation of molten droplets, which is the key to forming ZrB2+Amorphous microstructure. The formation of coating followed reaction-melting-liquid separation-deposition and solidification mechanism. The nanostructured ZrB2-ZrC composite coating with Al-O intergranular amorphous phase has excellent mechanical properties. The uniform nano-grains improved the hardness and the toughness of the ZrB2-ZrC eutectic. The ZrB2+Al-O amorphous microstructure obtained high toughness and the toughening mechanism was the crack deflection and crack branching caused by intergranular Al-O amorphous phase.

Exploring the toughening mechanisms of PyC interphase in SiCf/SiC composites through molecular dynamics and mesoscale stochastic simulations

The introduction of pyrolytic carbon (PyC) interphase in SiCf/SiC composites significantly improves their toughness, primarily by deflecting matrix cracks, while the underlying toughening mechanisms toward various PyC microstructures remain mysterious due to the challenges in experimentally observing microscopic deformations within PyC. This paper addresses this gap by constructing distinct PyC models based on orientation angle (OA), a key experimental characteristic, and then conducting Mode I loading simulations on SiCf/PyC/SiC systems by molecular dynamics (MD). Results indicate that as OA increases, the deformation behavior of PyC transits from multilayer sliding to delamination, which correlates to a reduction in the fracture energy of SiCf/PyC/SiC systems. Energy dissipation models are established for two microscopic deformation patterns as multilayer sliding and delamination based on homogenization theory, with results demonstrating that the energy dissipation caused by multilayer sliding within PyC surpasses that of delamination. Furthermore, mesoscale stochastic simulations of crack propagation in PyC with different textures are carried out to obtain crack path configurations and corresponding energy dissipations. The outcomes highlight the superior toughening effect of high texture (HT) PyC over medium texture (MT) and low texture (LT) PyC due to longer crack path within HT PyC, aligning well with experimental findings. This study provides valuable insights into cracking through PyC with varying textures, offering a foundation for optimizing PyC coating processes in SiCf/SiC composites to enhance performance.

Preparation and properties of Ta fiber reinforced high-entropy (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2-SiC composite ceramics

High-entropy boride ceramics are expected to be widely used in aerospace, automotive turbines, and armor protection due to their advantages of high melting point, high hardness, adjustable performance, high-temperature stability, and good oxidation resistance. However, it is urgent to solve the problem of low fracture toughness before application. Therefore, in this paper, a single-phase high-purity (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2 powder was prepared by boron/carbon thermal reduction method using a vacuum furnace. The effects of synthesis temperature and C content on the powder were studied. Secondly, HEB ((Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2) powder, SiC powder, and chopped Ta fiber were mixed uniformly, and Ta fiber toughened HEB-SiC composite ceramics were prepared by spark plasma sintering (SPS). The effects of Ta fiber content on the phase composition, microstructure, mechanical properties, and oxidation resistance of the composite ceramics were investigated. The results show that with the increase in synthesis temperature, the HEB powder gradually dissolves, and the solid solution is completely formed at 1700 °C. As the C content increases, the oxygen content and particle size of the powder gradually decrease. Single-phase high-entropy (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2 powders with high purity were prepared at 1700 °C for 1 h with 6 wt% C content. The addition of C will promote the boron/carbon thermal reduction method, reduce the oxygen content, and inhibit grain growth. With the increase of Ta fiber content, the density of HEB-SiC-Taf composite ceramics increased first and then decreased. The hardness gradually decreased, and the fracture toughness gradually increased. When the Ta fiber content was 7 vol%, the fracture toughness was the highest, reaching 5.12 ± 0.39MPa⋅m1/2, which was nearly 45 % higher than that of the composite ceramics without Ta fiber. This is because of the synergistic toughening mechanism of metal toughening and fiber toughening, such as crack deflection, crack bridging, fiber debonding, and fiber pullout, which improves the fracture toughness of the composite ceramics. With the increase in oxidation temperature, B2O3, SiO2, Ta2O5, and various metal oxides appear on the surface of HEB-SiC-Taf composite ceramics. The oxidation depth and weight gain per unit area gradually increase. When the Ta fiber content is 5 vol%, the composite ceramics exhibit the best high temperature stability and oxidation resistance. This is due to the Ta2O5 formed by the oxidation of Ta fibers, which dissolves into the B2O3 glass phase, increasing viscosity and improving high temperature stability while reducing the oxygen diffusion rate.

Tailoring mechanical and tribological properties of oscillatory pressure sintered binderless WC ceramics with expanded graphite addition

The fracture toughness and wear resistance of WC-based ceramics are crucial factors that determine their subsequent applications. In this study, the mechanical and tribological properties of expanded graphite (EG) reinforced WC ceramics consolidated by oscillatory pressure sintering (OPS) were investigated. The results demonstrated that the combination of dynamic pressure and EG had a synergistic effect, resulting in a much higher relative density of 0.2 wt% EG/WC ceramics reaching up to 99.78%. Simultaneously, 0.2 wt% EG/WC ceramics demonstrated a reduced grain size, with fracture toughness, flexural strength and wear rate reaching 7.54 MPa·m1/2, 1262 MPa and 2.16×10-7 mm3·N-1·m-1, respectively. EG was present in the form of graphene nanoplatelets (GNPs) within WC ceramics. The primary toughening mechanisms involved the bridging and pulling out of GNPs, as well as the generation of microcracks induced by GNPs. Additionally, the exceptional thermal conductivity of GNPs can facilitate heat dissipation and reduce thermal damage. The wear resistance of WC-EG ceramics was primarily enhanced through improving overall mechanical properties and decreasing the occurrence of oxidation and adhesive wear.

Effect of plastic deformability and fracture behaviour on interfacial toughening mechanism at Fe/Ni interfaces

Fracture at interface causes plastic deformation in the vicinity region. Conventional plastic energy dissipation theory indicates that ductile vicinity toughens the interface by absorbing plastic deformation energy. However, the microstructure in the vicinity directly affects local plastic deformability and fracture behaviour, implying a more complicated toughening mechanism. In this study, the effect of microstructure and hardness on fracture behaviour of Fe/Ni interface was investigated. By experimental approach, interfaces with and without dynamic recrystallization (DRX) were fabricated by controlling the bonding conditions. It showed that compression-induced plastic deformation is the main source of the hardening behaviour in the vicinity. Moreover, the interfaces with hardened DRX vicinities exhibited improved fracture toughness, which is inconsistent with the plastic energy dissipation theory. To clarify this observation, the crystal plasticity finite element method (CPFEM) approach was employed to distinguish the effects of plastic deformation and interfacial microstructure. The result showed that although higher plastic deformability in the vicinity absorbs more dissipated plastic energy, severe stress concentration at the interface leads to early fracture and poor toughness. On the other hand, the interfacial hardened DRXed grains disperse interfacial stress distribution and provide potential sub-crack sites. A combined result of uniform plastic deformation and fracture energy dissipation is responsible for the improved toughness at interfaces with DRXed grains.

A robust aerogel incorporated with phthalocyanine-based porous organic polymers for highly efficient gold extraction

The gold recovery from electronic waste liquid is of great significance to the recycling of precious metals and environmental restoration. Adsorption method is the preferred technique for gold recovery, but its expansion and application prospects were often limited by the workability and recyclability of common solid powder adsorbents. Herein, a solid absorbent powder (phthalocyanine-based POP, TD-POP) was integrated into chitosan/polyethyleneimine aerogel (TD-POP@CS/PEI-2) via a facile cross-linking and lyophilization strategy. As expected, TD-POP@CS/PEI-2 possessed outstanding mechanical toughness and stability, demonstrating efficient and specific adsorption for Au (III). The maximum adsorption capacity was 2169 mg g−1, higher than most of the absorbents. TD-POP@CS/PEI-2 aerogel also exhibited fast kinetics (recovery efficiency of 81.3 % within 3 h), good selectivity (recovery efficiency of 98.35 % at 10 times concentration of Al3+, Zn2+, Cu2+ Cd2+, Co2+, Ni2+, Mn2+, and Cr6+ than Au ions) and reusability (eight times). Multiple characterizations revealed the adsorption mechanism, which implied that the excellent adsorption properties of the aerogel were ascribed to the electrostatic attraction between cationic aerogel and AuCl4− anion, coordination interaction between nitrogen-containing active sites and Au (III), and reduction of Au (III) by TD-POP@CS/PEI-2 aerogel. This work provides a valuable and promising strategy to design scalable and sustainable adsorbents for capture precious metals, also promotes the development of integral adsorbent for environmental remediation.

Melamine formaldehyde resin adhesive toughened with graphene oxide: Structures and properties

The melamine-formaldehyde (MF) resin adhesive was modified by graphene oxide (GO), the chemical structure, wettability, bonding performance, tensile properties, curing performance and thermal properties of the modified resin were analyzed, and the toughening mechanism was also discussed in this study. The results showed that: (1) The MF resin with a high molar ratio possessed stable methylene ether bonds, which could easily generate parallel folding in space to form a π-π stacking supramolecular self-assembly special structure, with the potential of enhancing the toughness of molecular structures. (2) GO contained a large number of oxygen-containing reactive functional groups, which could further lower the curing temperature of the MF resin. A dense cross-linked network structure improved the thermal stability of the resin. (3) The bonding strength and toughness of the resin were significantly improved when the content of GO was 0.1 wt%. However, due to the large specific surface area and the intense π-π interaction between sheets, GO was easy to agglomerate, and the properties of the resin with GO content of 0.4 wt% degraded sharply. (4) The crystallinity of the MF resin modified by GO decreased, and the surface energy and plastic deformation energy increased due to the increased fracture crack path and fracture surface of the resin, which was the macro-reason for the improvement of toughness. (5) The strong π-π interaction between GO sheets and π-π accumulation between triazine rings were like parallel “springs” in the molecular structure of the resin, which might be the internal reason for the improvement of toughness. In addition, it was also proved that this special structure could limit the activity of hydroxymethyl and the release of free formaldehyde in the resin.

Superior fracture resistance and topology-induced intrinsic toughening mechanism in 3D shell-based lattice metamaterials.

Lattice metamaterials have demonstrated remarkable mechanical properties at low densities. As these architected materials advance toward real-world applications, their tolerance for damage and defects becomes a limiting factor. However, a thorough understanding of the fracture resistance and fracture mechanisms in lattice metamaterials, particularly for the emerging shell-based lattices, has remained elusive. Here, using a combination of in situ fracture experiments and finite element simulations, we show that shell-based lattice metamaterials with Schwarz P minimal surface topology exhibit superior fracture resistance compared to conventional octet truss lattices, with average improvements in initiation toughness up to 150%. This superiority is attributed to the unique shell-based architecture that enables more efficient load transfer and higher energy dissipation through material damage, structural plasticity, and material plasticity. Our study reveals a topology-induced intrinsic toughening mechanism in shell-based lattices and highlights these architectures as a superior design route for creating lightweight and high-performance mechanical metamaterials.

Tough double-bouligand architected concrete enabled by robotic additive manufacturing

Nature has developed numerous design motifs by arranging modest materials into complex architectures. The damage-tolerant, double-bouligand architecture found in the coelacanth fish scale is comprised of collagen fibrils helically arranged in a bilayer manner. Here, we exploit the toughening mechanisms of double-bouligand designs by engineering architected concrete using a large-scale two-component robotic additive manufacturing process. The process enables intricate fabrication of the architected concrete components at large-scale. The double-bouligand designs are benchmarked against bouligand and conventional rectilinear counterparts and monolithic casts. In contrast to cast concrete, double-bouligand design demonstrates a non-brittle response and a rising R-curve, due to a hypothesized bilayer crack shielding mechanism. In addition, interlocking behind and crack deflection ahead of the crack tip in bilayer double-bouligand architected concrete elicits a 63% increase in fracture toughness compared to cast counterparts.

Synthesis, mechanical characterization, and biocompatibility evaluation of Graphene-TiO2 reinforced alumina for biomedical applications

The study addresses the limited fracture toughness of Al2O3 ceramics by developing graphene-TiO2 reinforced alumina nanocomposites through pressing. Mechanical properties, including hardness, fracture toughness, and elasticity, were examined, alongside the structural characterization via XRD analysis and microstructure evaluation using SEM. Cytotoxicity and cell adhesion tests were conducted for in vitro biological evaluation. The inclusion of a graphene additive led to a nearly threefold increase in fracture toughness, reaching up to 8.161 MPa m1/2. Graphene doping induced a discernible shift to lower angles in the XRD pattern, revealing the presence of Al2O3, Al2TiO5, and TiO2 phases. Samples immersed in artificial body fluid for 14 days exhibited minimal ion release, with Titanium ion below 0.001 mg/L and aluminum ion below 0.05 mg/L, indicating a lack of significant ion release. The cytotoxic activity of the samples against NIH/3T3 cells was assessed through Alamar Blue analysis, revealing no significant change in cell viability after 48 h of exposure.

Effect of grain morphology and interface on the toughness of nacre-like aluminas

Ceramic composites that are both tough and strong are needed for extreme environments, ranging from aerospace and nuclear, to medical applications. Bioinspired ceramic composites tackle this challenge by mimicking tough natural structures. Nacre-like aluminas (NLAs) are ceramics processed using advanced colloidal techniques to obtain a microstructure resembling the brick-and-mortar structure of nacre. NLAs can achieve flexural strengths up to 600 MPa and fracture toughnesses ranging from 5 MPa.m1/2 up to 16 MPa.m1/2 after crack propagation. These high values mainly rely on deflection mechanisms; these can operate at temperatures up to 1200°C and under impact testing. The fracture properties have been found to be highly dependent on the mortar composition and processing technique used. However, we still don't know how far we can extend the structural properties of NLAs by changing their mortar strength and brick morphology. In this study, we combine mode I wedge splitting testing and in situ synchrotron X-ray microtomography of mixed-mode SENB fracture testing along with a kinked crack analytical formulation to study the microstructure-properties relationship in NLAs having two mortar compositions/morphologies. We compare the toughness values obtained in mode I and II with deflection models and study the effect of mode-mixity on the NLA toughness. Our findings show the grain morphology strongly influences the fracture behaviour, with the longer grain material showing longer stable crack deflection which could be further optimised going forwards. By contrast the mortar properties which provide deflection and local toughening mechanisms may be nearing their optimal strength.

Collaboration of β-crystals and rubbery phases in polypropylene random copolymer for toughening

Polypropylene random copolymer (PPR) is in high demand for pipelines due to its comprehensively brittle-ductile balance. It is a multiphase polymer composed of crystalline phases and rubbery phases in which improving the quantities of ductile β-crystals can effectively toughen PPR. However, the influence of β-crystallization on the aggregation of rubbery phases and their collaboration for toughening are still not well elucidated. In this work, the toughening mechanism of PPR/iPP/β-NA composites were illustrated by manipulating the crystallization and phase separation behaviors using different molecular weight of isotactic polypropylene (iPP) and β-nucleating agent (β-NA). A high relative β-crystal content (Kβ) was obtained in PPR/iPP/β-NA composites and the influence of molecular weight of iPP on crystal structures of PPR/iPP/β-NA composites was investigated via differential scanning calorimetry (DSC) and x-ray diffraction (XRD). The phase separation behaviors were then studied using rheological measurements and scanning electron microscope (SEM). The impact behaviors of PPR/iPP/β-NA composites with similar crystal structures but different size of rubbery particles were demonstrated. It was found that crystallization of PPR into β-crystal promoted the phase separation process and the resulting rubbery particle size. The deformation of large rubbery particles induced small wavy cracks at the fracture surface other than layered cracks for small rubbery particles. This work basically introduces the toughening mechanism from collaboration of β-crystals and rubbery phases in polypropylene random copolymers and provides a new method for fabricating high toughness PPR pipe.

Jellyfish‐Inspired Polyurea Ionogel with Mechanical Robustness, Self‐Healing, and Fluorescence Enabled by Hyperbranched Cluster Aggregates

AbstractIonogels are promising for soft iontronics, with their network structure playing a pivotal role in determining their performance and potential applications. However, simultaneously achieving mechanical toughness, low hysteresis, self‐healing, and fluorescence using existing network structures is challenging. Drawing inspiration from jellyfish, we propose a novel hierarchical crosslinking network structure design for in situ formation of hyperbranched cluster aggregates (HCA) to fabricate polyurea ionogels to overcome these challenges. Leveraging the disparate reactivity of isocyanate groups, we induce the in situ formation of HCA through competing reactions, enhancing toughness and imparting the clustering‐triggered emission of ionogel. This synergy between supramolecular interactions in the network and plasticizing effect in ionic liquid leads to reduced hysteresis of the ionogel. Furthermore, the incorporation of NCO‐terminated prepolymer with dynamic oxime–urethane bonds (NPU) enables self‐healing and enhances stretchability. Our investigations highlight the significant influence of HCA on ionogel performance, showcasing mechanical robustness including high strength (3.5 MPa), exceptional toughness (5.5 MJ m−3), resistance to puncture, and low hysteresis, self‐healing, as well as fluorescence, surpassing conventional dynamic crosslinking approaches. This network design strategy is versatile and can meet the various demands of flexible electronics applications.

The robustness waterproof ionogel based on the phase separation to form soft hard heterostructures and the interaction of cation-π realizes underwater adhesion and sensing

Flexible ionic conductors hold significant promise for advancing the field of soft ion electronics in the future. However, the creation of flexible conductors that possess mechanical robustness, underwater adhesion and underwater motion monitoring remains a challenge. Drawing inspiration from the multiphase hetero structure found in biological connective tissues, such as high modulus fibers and low modulus water-rich matrices, this article proposes a one-pot polymerization in-situ design strategy to create a hydrophobic ionogel with a hetero structure of soft and hard domains. The mechanical robustness, elasticity, and toughness of the ionogel are achieved through a synergistic combination of a strong skeleton in the hard domain and an elastic matrix in the soft domain. Additionally,hydrophobic aromatic rings and quaternary ammonium cation simulated cation-π interactions in mussel foot silk protein. Upon contact with water, the hydrophobic clusters quickly aggregate, facilitating the expulsion of interfacial water and exposing salicylic acid groups and quaternary ammonium cationic groups, leading to outstanding underwater adhesion between the ionogel and various substrates. The resulting hydrophobic ionogel can be utilized in underwater wearable electronic devices for monitoring human movement and physiological information, underwater repair monitoring, and intelligent soft robotics, demonstrating its vast potential in the field of underwater sensors.

Horn sheath-inspired lightweight composites with enhanced impact resistance

The natural Caprinae horn sheaths possess excellent mechanical properties due to the synergistic effects of the porous and corrugated lamellar structure. However, research on bioinspired designs based on this structure remains absent. In this work, we attempted to integrate hollow glass microspheres modified by silane coupling agents into A. pernyi silk fabric, and finally fabricate a horn sheath-inspired composite using the vacuum-assisted resin transfer molding. The impact strength of the horn sheath-inspired composite reaches up to 150 kJ m-2 with a low density of 1290 kg m-³. Fracture morphology analysis and finite element simulation confirmed the toughening mechanisms, including crack deflection and interfacial bonding due to the synergistic effects of the porous structure and the corrugated silk fabrics. This study provides a bioinspired strategy to lightweight and tough composites, with significant potential in impact-critical applications.

Diffusion enhancement by spontaneous formation of Frenkel defects in NaCl-type high-entropy materials

High-entropy materials (HEMs) are attracting attention due to their exceptional properties, such as enhanced mechanical toughness, irradiation resistance, ionic conductivity, and thermoelectric performance. Although diffusion is an important phenomenon as it is closely related to these physical properties of materials, there is a lack of understanding of the mechanisms of diffusion due to the complexity of the atomic interactions in HEMs. Here, we investigates diffusion mechanisms in PbTe-based HEMs AgInSnPbBiTe5, focusing on the role of indium (In). Molecular dynamics simulations reveal that In+ spontaneously forms Frenkel defect and enhancing diffusion not only of In+ but also other cations. Furthermore, as a result of enhanced diffusion, short-range order is formed by structural relaxation. This insight not only enhances comprehension of HEMs diffusion mechanisms but also develops HEMs with properties such as self-healing from damage and high ion permeability, advancing the field of material science.

Nano-scale modeling of energy dissipation in a single lamella reveals the significant contribution of collagen-mineral sliding to intrinsic bone toughness

Although collagen-mineral sliding is recognized as one of the intrinsic mechanisms that contribute to the bone toughness, its precise role in energy release at the nano-scale, as well as its relationship to other intrinsic toughness mechanisms, remains unclear. This lack of understanding stems from the challenges associated with quantifying the specific nature of contact at the mineral-collagen interface, and the energy dissipation capacity resulting from plastic deformation at this scale. To address this issue, we developed a three-dimensional model of mineralized collagen fibril using ABAQUS, incorporating hyperelastic isotropic collagen, elastic isotropic mineral, and a cohesive contact formulation to represent the collagen-mineral interface. Knowing the properties of collagen and mineral and using a parametric modeling approach, we estimated the properties of contact based on experimental measurements of the stress-strain behavior in a single bone lamella, considering the angle of the collagen fibril in relation to the loading axis. By comparing the experimental elastic modulus with the model predictions, we determined that the cohesive contact exhibited a maximum strength of 9 MPa and a fracture energy of 50 mJ/m2 within the bone. Further analysis indicated that fracture energy at the collagen-mineral interface is potentially closer to 5 mJ/m2. Using these findings, we concluded that the interfaces were responsible for 52% to 98% of the energy release in mineralized collagen fibrils, depending on collagen angle, both directly and indirectly by influencing stress and strain in adjacent collagen fibril. The results of this study demonstrated that plastic deformation at the collagen-mineral interface is the primary mechanism underlying bone toughness at the nano-scale. Importantly, we found that these conclusions held true regardless of the angle of the collagen fibril relative to the loading axis. The modeling framework presented in this study provides a valuable tool for investigating the elastic and post-yield behavior of bone across different mineral volume fractions at the nano-scale, and at the lamellar level.

The fracture and toughening mechanism of double-network hydrogel using the network mechanics method

Double-network hydrogels have received considerable attention due to their superior mechanical properties. However, a comprehensive understanding of their fracture and toughening mechanisms is still lacking, primarily due to the complex network structures of double-network hydrogels and the highly non-linear characteristics of the fracture. In this study, we address this gap by developing a mesoscopic model for double-network hydrogels using the network mechanics method, in which the fracture of polymer chains is realized by introducing the stretch criterion to each polymer chain. Through numerical analysis, we find that the stretch criterion ratio of polymer chains in two networks λ2c/λ1c is the key factor that influences the necking and hardening phenomena of double-network hydrogels. By changing this stretch criterion ratio, the fracture mode of double-network hydrogels can transit between ductile and brittle. When the fracture stretching criteria of the polymer chains in the first and second networks are 1.8 and 6, the necking and hardening phenomena can be observed. It is also found that a more uniform network structure of the first network enhances the toughness of double-network hydrogels. This study sheds light on the fundamental fracture and toughening mechanisms of double-network hydrogels, providing new insights for their further applications.

Influence of nanofiller surface treatment on mechanical properties of pyrolyzed ceramic nanocomposites

The brittleness and limited plastic deformation of ceramics restrict their applications. In this work, the effects of pristine (CNTP), functionalized (CNTOH, CNTCOOH) and silanized MWCNTs on the mechanical properties of Silicon Carbide obtained by pyrolyzing polycarbosilane SMP-10 were studied. Functionalization with 3-glycidoxypropyltrimethoxy was analyzed through dispersion stability, zeta potential, and EDS analyses, revealing increased silicon content and colloidal stability in silanized MWCNTs. However, silanized MWCNTs led to reduced mechanical properties in composites, while untreated MWCNTs (CNTP, CNTOH, CNTCOOH), showed a substantial increase in modulus by 74.2 %, 86.9 %, and 30.5 %, respectively. The observed enhancement in mechanical properties exceeded the outcomes predicted by the rule of mixtures, suggesting notable morphological changes induced by MWCNTs. Potential underlying factors including toughening mechanisms and changes in porosity were evaluated and discussed in depth. Composites with untreated MWCNTs showed nearly a two-fold increase in fracture toughness. This work shows a streamlined approach for the development of ceramic nanocomposites (CNCs), achieving significant improvement in mechanical properties through pyrolysis, surpassing traditional methods reliant on densification processes. These findings demonstrate the substantial potential of CNCs, enhancing their suitability for advanced engineering applications.

Understanding Toughening Mechanisms and Damage Behavior in Hybrid-Fiber-Modified Mixtures Using Digital Imaging

Pavement cracking is a primary cause of early damage in asphalt pavements, and fiber-reinforcement technology is an effective method for enhancing the anti-cracking performance of pavement mixtures. However, due to the multi-scale dispersed structure of pavement mixtures, it is challenging to address cracking and damage with a single fiber type or fibers of the same scale. To investigate the toughening mechanisms and damage behavior of hybrid-fiber-modified mixtures, we analyzed the fracture process and damage behavior of these mixtures using a combination of basalt fiber and calcium sulfate whisker hybrid fiber modification, along with semicircular bending tests. Additionally, digital imaging was employed to examine the fracture interface characteristics, revealing the toughening mechanisms at play. The results demonstrated that basalt fibers effectively broaden the toughness range of the modified mixture at the same temperature, reduce mixture stiffness, increase residual load at the same displacement, and improve crack resistance in the mixture matrix. While calcium sulfate whiskers enhanced the peak load of the mixture, their high stiffness modulus was found to be detrimental to the mixture’s crack toughness. The fracture interface analysis indicated that the three-dimensionally distributed fibers form a spatial network within the mixture, restricting the relative movement of cement and aggregate, delaying crack propagation, and significantly improving the overall crack resistance of the mixture.