Maximum Modulus Research Articles

Dynamic structural characteristics and vibration susceptibility of Tongren loess under the influence of water content and confining pressure

Loess is extensively developed on both sides of the Longwu River, a tributary of the Yellow River, Tongren County, Qinghai Province. The engineering geological characteristics are complex, and landslide disasters are highly developed. Based on field geological surveys and physical property analysis of the loess in this area, this study analyzes the influence of water content, consolidation pressure, and soil disturbance on the dynamic characteristics of loess using GDS dynamic triaxial tests. The results show that Tongren loess has strong structural properties. Its dynamic constitutive relationship conforms to the Hardin-Dinevich hyperbolic model, where the parameters a and b decrease with increasing confining pressure and increase with increasing water content. The dynamic cohesion and dynamic friction angle both decrease with increasing water content, with the dynamic cohesion significantly affected, decreasing by 77% ~ 83% when saturated. However, the dynamic friction angle is less affected by water content changes, decreasing by 18% ~ 25% when saturated. Under dynamic conditions, the dynamic friction angle of Tongren loess is only 12 ~ 16°, making slopes composed of Tongren loess highly susceptible to instability and sliding under strong earthquake conditions. The dynamic structural properties of Tongren loess are significantly influenced by water content, with increasing water content destroying the joint structural strength of intact loess. Before reaching the plastic limit water content, the joint structural strength of intact loess decreases sharply with increasing water content, and then decreases slowly. The frictional structural strength shows an opposite trend. Under the same experimental conditions, the failure dynamic stress, maximum dynamic elastic modulus, and dynamic shear strength parameters of intact loess are generally greater than those of remolded loess, and the differences between them decrease with increasing water content. This study provides insights into the dynamic structural characteristics of Tongren loess, which can serve as a reference for understanding the formation mechanisms, stability analysis, and seismic design of loess landslides in the region.

The Small-Strain Stiffness Properties of Clay-Gravel Mixture Subjected to Freeze-Thaw Cycles

Abstract In this paper, the resonant column tests were utilized to examine the small-strain stiffness and attenuation of clay-gravel mixture (CGM) under various effective consolidation pressures and freeze-thaw cycles, on the basis of investigating the electrical resistivity variation trend of CGM samples undergoing various freeze-thaw cycles. It is shown that the resistivity of CGM tends to stabilize when the freeze-thaw cycles (N) reach 9, and, thus, the samples after 0, 3, 6, 9, and 12 cycles were selected for resonance column testing. The results show that, once N > 9, the decay in dynamic shear modulus demonstrates a weakened association with N and the stiffness degradation effect of freezing-thawing would be weakened and inhibited by high effective consolidation stress. Additionally, a mathematical model was constructed to predict the maximum dynamic shear modulus (Gmax) in the basis of freeze-thaw cycles and effective consolidation stress. Microscopic analysis results suggest that the freeze-thaw effect on CGM lies in the development of soil aggregates and porosity variation within the fine-grained soil. Compared to gravel soils and frozen soil, the cementation of matrix soil and the effect of blocky structure are considered as fundamental reasons for the improved small-strain stiffness and reduced vulnerability to freeze-thaw cycles of CGM.

Effect of Al contents on the microstructure and cavitation erosion resistance of TiSiN/NiTiAlxCrCoN nanomultilayer films

Abstract The TiSiN/NiTiAlxCrCoN nanomultilayer films were grown on 304 stainless steels through magnetron sputtering system. The microstructure and cross-sectional and surface images, mechanical and cavitation erosion properties of the prepared films were explored in detail. The results of the study reveal that all TiSiN/NiTiAlxCrCoN nanomultilayer films exhibit a face-centered cubic structure with a preferential orientation in (200) plane. The cross-sectional images of films show the columnar structure. The values of elastic modulus, hardness, and adhesive strength for the TiSiN/NiTiAlxCrCoN nanomultilayer films initially increase and later decrease as the Al content is increased, whereas the mass loss for the TiSiN/NiTiAlxCrCoN nanomultilayer films initially decrease and later increase during the cavitation erosion experiment. The TiSiN/NiTiAl0.8CrCoN nanomultilayer film provides a maximum hardness value equal to 31.3 GPa, a maximum elastic modulus equal to 218.9 GPa, a highest adhesive strength equal to 38.8 N and a least mass loss equal to 0.8 mg. The study showed that the solid solution strength and the alternating stress field enhance the properties of the TiSiN/NiTiAlxCrCoN nanomultilayer films.

Predicting Flexural Properties of 3D-Printed Composites: A Small Dataset Analysis Using Multiple Machine Learning Models

Fused Deposition Modelling (FDM) is a common Additive Manufacturing (AM) technique for processing polymers and composites. Infill density is one of the crucial parameters affecting the mechanical properties of the processed materials/structures. In material science, the availability of large experimental datasets acquired under the same conditions is a costly and time-consuming practice. To address this issue, the present work focuses on deploying five machine learning models including Linear Regression (LR), Polynomial Regression (PR), Gaussian Process Regression (GPR), Gradient Boosting (GB), and Random Forest (RF) to test their prediction capabilities with a small experimental flexural load-extension dataset of Short Carbon Fiber Reinforced PLA (CF-PLA) consisting of only 550 records. Experimental results yielded a direct relation between the infill density and flexural performance of CF-PLA. An increase of 308%, 280%, and 94% was observed for maximum flexural load, flexural strength, and flexural modulus, respectively. Following this, to access and compare the performance of each ML model in forecasting these improvements, Mean Absolute Error (MAE), Root Mean Squared Error (RMSE), and R-squared (R2) metrics were used. The results revealed that the Random Forest (RF) algorithm successfully predicted material behavior with an MAE, RMSE, and R2 of only 0.64, 1.17, and 0.99, respectively. Whereas, LR was found to be least effective in capturing the complex behavior of the composite with an MAE, RMSE, and R2 of 6.94, 9.71, and 0.82, respectively. Thereby indicating the efficacy of the RF algorithm for even smaller data sets.

Generalized partial-slice monogenic functions

The two function theories of monogenic and of slice monogenic functions have been extensively studied in the literature and were developed independently; the relations between them, e.g. via Fueter mapping and Radon transform, have been studied. The main purpose of this article is to describe a new function theory which includes both of them as special cases. This theory allows to prove nice properties such as the identity theorem, a Representation Formula, the Cauchy (and Cauchy-Pompeiu) integral formula, the maximum modulus principle, a version of the Taylor series and Laurent series expansions. As a complement, we shall also offer two approaches to these functions via generalized partial-slice functions and via global differential operators. In addition, we discuss the conformal invariance property under a proper group of Möbius transformations preserving the partial symmetry of the involved domains.

Preliminary study on the preparation of lyophilized acellular nerve scaffold complexes from rabbit sciatic nerves with human umbilical cord mesenchymal stem cells.

The gold standard of care for patients with severe peripheral nerve injury is autologous nerve grafting; however, autologous nerve grafts are usually limited for patients because of the limited number of autologous nerve sources and the loss of neurosensory sensation in the donor area, whereas allogeneic or xenografts are even more limited by immune rejection. Tissue-engineered peripheral nerve scaffolds, with the morphology and structure of natural nerves and complex biological signals, hold the most promise as ideal peripheral nerve "replacements". To prepare allogenic peripheral nerve scaffolds using a low-toxicity decellularization method, and use human umbilical cord mesenchymal stem cells (hUC-MSCs) as seed cells to cultivate scaffold-cell complexes for the repair of injured peripheral nerves. After obtaining sciatic nerves from New Zealand rabbits, an optimal acellular scaffold preparation scheme was established by mechanical separation, varying lyophilization cycles, and trypsin and DNase digestion at different times. The scaffolds were evaluated by hematoxylin and eosin (HE) and luxol fast blue (LFB) staining. The maximum load, durability, and elastic modulus of the acellular scaffolds were assessed using a universal material testing machine. The acellular scaffolds were implanted into the dorsal erector spinae muscle of SD rats and the scaffold degradation and systemic inflammatory reactions were observed at 3 days, 1 week, 3 weeks, and 6 weeks following surgery to determine the histocompatibility between xenografts. The effect of acellular scaffold extracts on fibroblast proliferation was assessed using an MTT assay to measure the cytotoxicity of the scaffold residual reagents. In addition, the umbilical cord from cesarean section fetuses was collected, and the Wharton's jelly (WJ) was separated into culture cells and confirm the osteogenic and adipogenic differentiation of mesenchymal stem cells (MSCs) and hUC-MSCs. The cultured cells were induced to differentiate into Schwann cells by the antioxidant-growth factor induction method, and the differentiated cells and the myelinogenic properties were identified. The experiments effectively decellularized the sciatic nerve of the New Zealand rabbits. After comparing the completed acellular scaffolds among the groups, the optimal decellularization preparation steps were established as follows: Mechanical separation of the epineurium, two cycles of lyophilization-rewarming, trypsin digestion for 5 hours, and DNase digestion for 10 hours. After HE staining, no residual nuclear components were evident on the scaffold, whereas the extracellular matrix remained intact. LFB staining showed a significant decrease in myelin sheath composition of the scaffold compared with that before preparation. Biomechanical testing revealed that the maximum tensile strength, elastic modulus, and durability of the acellular scaffold were reduced compared with normal peripheral nerves. Based on the histocompatibility test, the immune response of the recipient SD rats to the scaffold New Zealand rabbits began to decline3 weeks following surgery, and there was no significant rejection after 6 weeks. The MTT assay revealed that the acellular reagent extract had no obvious effects on cell proliferation. The cells were successfully isolated, cultured, and passaged from human umbilical cord WJ by MSC medium, and their ability to differentiate into Schwann-like cells was demonstrated by morphological and immunohistochemical identification. The differentiated cells could also myelinate in vitro. The acellular peripheral nerve scaffold with complete cell removal and intact matrix may be prepared by combining lyophilization and enzyme digestion. The resulting scaffold exhibited good histocompatibility and low cytotoxicity. In addition, hUC-MSCs have the potential to differentiate into Schwann-like cells with myelinogenic ability following in vitro induction.

Optimizing printability and mechanical properties of poly(3-hydroxybutyrate) (P3HB) biocomposite blends and their biological response to Saos-2 cells

Bone tissue engineering requires scaffolds with three-dimensional structures that facilitate vascularization and new tissue growth. 3D printing, especially through fused deposition modeling (FDM), has emerged as an effective method for creating complex structures with high reproducibility. Early research in this area demonstrated the potential of poly(ε-caprolactone) (PCL) and poly(L-lactide) (PLLA) scaffolds for bone regeneration. Recently, polylactide (PLA) and polyhydroxyalkanoates (PHAs) have garnered attention for their biocompatibility and ability to support cell proliferation. Among PHAs, poly(3-hydroxybutyrate) (P3HB) shows promise due to its intrinsic biocompatibility and resorbability, making it a candidate for FDM-based scaffold fabrication. In the presented study, we aim to develop and optimize a biocompatible P3HB-based composite material for bone tissue engineering, incorporating PLA, hydroxyapatite (HA), and the plasticizer Syncroflex3114 (SN) to enhance mechanical properties and printability. This composite was processed into filaments for 3D printing and characterized through thermal, mechanical, and biological evaluations. Using a design of experiment (DoE) approach, we investigated factors such as temperature performance, warping, degradation, and strength to determine the optimal composition for use in tissue engineering. Four optimal mixture compositions fulfilling the optimization criteria of having the most suitable properties for bone tissue engineering, namely the best printability and maximum mechanical properties,  were obtained. The mixtures were optimized specifically for minimum warping coefficient (0.5); maximum flexural strength (66.9 MPa); maximum compression modulus (2.4 GPa); and maximum compression modulus (2.3 GPa) with a warping coefficient of no more than one at the same time. In conclusion, the study shows a new possible way to effectively develop and test 3D printed P3HB-based scaffolds with specifically optimized material properties.

Evaluation of Benign and Malignant Cervical Lymphadenopathy: A Comparative Study of Shear Wave Elastography and Grayscale Ultrasound

Abstract Objectives The aim of the study was to evaluate role of shear wave elastography (SWE) using a novel methodology for differentiation of benign and malignant cervical lymph nodes. Methods SWE was performed on 38 patients who presented with cervical lymph adenopathy. Color-coded elasticity maps were obtained, from which the stiffest region of interest (ROI) with a diameter of 2 mm was chosen. Maximum and mean Young's modulus values (Kpa) were calculated in selected 2-mm ROI. Finally, the results were correlated with the fine needle aspiration cytology findings in all patients to assess the diagnostic accuracy, sensitivity, and specificity at a defined cutoff value for distinguishing between benign and malignant lymphadenopathies. Results There were 20 malignant cervical lymph nodes and 18 benign cervical lymph nodes. Malignant nodes showed significantly higher mean Young's modulus value (154.2 ± 46.19 kPa) compared with benign nodes (70.39 ± 30.76 kPa), with a p-value of less than 0.0001. Our findings indicate that the mean Young modulus value within a standardized 2-mm ROI outperformed grayscale ultrasound in terms of diagnostic accuracy (92.1 vs. 78.9%), sensitivity (100 vs. 80%), and specificity (83.3 vs. 77.7%), with the established cutoff values for high diagnostic accuracy indicating malignancy as greater than 92 for mean Young's modulus with an area under the curve of 0.964. Conclusion SWE using a standardized 2-mm ROI provides improved sensitivity and diagnostic accuracy for differentiation of benign and malignant lymph node lesions.

Experimental study on the impact of hybrid GFRP composites with graphene oxide and silicon carbide fillers on mechanical and wear properties

Recently, there has been a rapid increase in the demand for manufacturing reliable and innovative components. FRP composites are ideal for various engineering applications due to their low cost, lightweight, high strength-to-weight ratio, mechanical properties, and heat resistance. This research focuses on fabricating GFRP composites with graphene oxide (GO) and silicon carbide (SiC) fillers using the hand-layup method. Mechanical tests were performed using UTM, and wear testing was conducted through fretting wear analysis. The outcomes reveal that the optimal mechanical characteristics, including tensile strength, flexural strength, and short beam strength (SBS), were 242.73 MPa, 317.13 MPa, and 40.05 MPa, respectively, at a 0.5 wt.% GO filler concentration. The laminate composite achieved a maximum tensile and flexural modulus of 8.03 GPa and 13.59 GPa correspondingly with the incorporation of 0.5% GO micro-fillers to the epoxy matrix with respect to the NE composite, due to improved interfacial bonding between the matrix and filler. Additionally, the best wear resistance in the laminate composite was observed with a hybrid micro-filler combination of 1% SiC and 1% GO introduced into the polymer matrix, leading to minimal material removal from the GFRP laminate composite. The worn surfaces of the composites were analyzed using (FE-SEM) to explore potential wear mechanisms. It was revealed that during the initial phases of wear, the participation of the fillers plays a substantial role in the GFRP composite. The introduction of hybrid fillers into composite renders it an encouraging material for industrial purposes requiring exalted strength and exceptional wear resistance.

Dynamic properties of alkali residue-based foamed concrete under dry-wet cycles

Alkali residue-based foamed concrete (A-FC) is a lightweight and sustainable building material made from cement, alkali residue, blast furnace slag and foam. The dynamic properties under dry-wet cycles and confining pressure are essential considerations for the engineering application of A-FC. Dynamic triaxial tests were used in this study to explore the influence of dry-wet cycles and confining pressure on the backbone curves, damping ratio, and dynamic elastic modulus of A-FC. A calculation model was established to illustrate the combined effects of confining pressure and dry-wet cycles on the maximum dynamic elastic modulus. Test results indicate that during dry-wet cycles, the coupling effects of temperature, expansion force, and osmotic pressure cause vulnerable pore walls to rupture, pores to become rougher, and microcracks to develop. The backbone curves demonstrate elastoplastic deformation, with no significant change in shape caused by the dry-wet cycles. As the number of dry-wet cycles increases, internal damage accumulates, resulting in a weakening of dynamic deformation ability and a decline in the dynamic elastic modulus. The damping ratio rises with the number of dry-wet cycles once the axial dynamic strain surpasses the transitional strain. Increasing confining pressure can mitigate the adverse impacts of dry-wet cycles on dynamic performance. A-FC demonstrates remarkable durability and favorable dynamic performance, supporting its widespread application in diverse environments.

PH-sensitive aminated chitosan/carboxymethyl cellulose/aminated graphene oxide coated composite microbeads for efficient encapsulation and sustained release of 5-fluorouracil

The application of smart pH-sensitive carriers has become an ideal choice for administering drugs with desired release profiles. Although pH-sensitive microbeads offer distinct benefits for delivering anticancer drugs orally, they encounter drawbacks, including low encapsulation efficiency, weak mechanical stability, biocompatibility concerns, and the risk of abrupt release. This study focuses on developing pH-sensitive coated composite microbeads for effective encapsulation and sustained release of 5-fluorouracil (5-FU). Aminated graphene oxide (AmGO) was integrated into carboxymethyl cellulose (CMC) microbeads, which were subsequently coated with an aminated chitosan (AmCs) derivative. Various analysis techniques, including Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analyzer (TGA), zeta potential (ZP), and mechanical testing, were utilized to characterize the microbeads. The AmCs@CMC@AmGO composite microbeads demonstrated a compact structure with enhanced mechanical properties, achieving a maximum Young's modulus value of 35.99 N/mm2 compared to 25.95 N/mm2 for pure CMC microbeads. Moreover, pH-sensitivity and water uptake studies (at pH 1.2 and pH 7.4) revealed significant tunability of the composite microbeads by altering the AmGO and AmCs ratios. The coated composite microbeads encapsulated approximately 86.4 % of 5-FU compared to 47 % for CMC microbeads. The burst release of 5-FU at pH 7.4 was significantly reduced, with sustained release reaching 51 % over 24 h. The predominant release mechanism was Fickian diffusion, which well-described by the Peppas-Sahlin kinetic model. The developed microbeads exposed improved biodegradability and non-toxicity toward normal colon cells, while exhibiting notable toxicity against cancerous cells, emphasizing its potential for anticancer drug delivery.

Synthesis and characterization of new continuous phosphate glass fibers intended for structural engineering applications: Structure/property relationships

Nowadays, phosphate glass fibers (PGF) are considered quite competitive respective to conventional glass fibers. This work focus on the development of PGF fibers intended for structural engineering applications such as composite reinforcement for building and automotive fields. For this purpose, two series of phosphate glasses based on 52P2O5-24CaO-13MgO-(11-(X+Y+Z)) K2O-XAL2O3-YF2O3-ZTiO2; (X=1; 3; 5, Y=0; 5, Z=0; 1 mol %) were processed and transformed into phosphate glass fibers by melt spinning. The resulting fibers were characterized. XRD analysis confirmed the non-crystalline nature of phosphate glasses. In addition, the substitution of K2O by Al2O3 and by the combination of Al2O3, Fe2O3 and TiO2 in the composition of phosphate glass could lead to a significant increase in fiber density from 2,16 g/cm3 to 2,80 g/cm3. The stability of the produced phosphate glass fibers was examined using two methods: weight loss at 37°C and dissolution kinetics under different pH levels (4, 7, and 12). The results showed that the chemical resistance of the PGF fibers was improved with up to 99% increase respective to the original formulation. In addition, the mechanical properties of the spinnable phosphate glass manufactured by replacing K2O oxide by Al2O3 oxide were improved, such a substitution led to a maximum tensile strength and modulus of 2668 MPa and 140 GPa, respectively. Therefore, the tensile proprieties were improved by 75% compared to the original formulation. This comparative study between phosphate glass fibers (PGF) and traditional fibers highlight similar tensile strength but combined to notable enhancements in chemical stability through cation addition, expanding their potential use in composite and biomedical materials. Finally, a correlation analysis of mechanical performances was carried out. It was observed that the results obtained using the statistical methods were consistent with the experimental data.

Fabrication and testing of PVDF-Fish scales based sustainable piezoelectric impact sensor

Structural health monitoring is essential to modern infrastructure management, ensuring safety, optimizing costs, and enhancing structures' overall performance and reliability. Leftover fish scales (FS) in varying quantities (5, 10, 15, and 20wt.%) are reinforced into a polyvinylidene fluoride (PVDF) matrix to develop highly flexible piezoelectric composites, which are then assessed as impact sensors. The role of FS loading on the mechanical and dielectric behavior of PVDF is also investigated. PVDF with 10% FS loading showed maximum Ultimate tensile strength (UTS) and Elastic modulus (E) of 37MPa and 1192MPa, respectively. A 56% and 67% enhancement in UTS and E values over pure PVDF matrix is recorded. Piezoelectric nanogenerators (PENGs) are then fabricated to check the piezo response of composites under various loading conditions using a human hand (finger tapping, palm tapping, film twisting, and wrist pressing). The device with a maximum piezo response is further assessed for potential impact sensing under different impact loading conditions. The recorded results are analyzed statistically using the Weibull distribution approach to cater to the o/p voltage variations for each test load. The potential for sustainability and circular economies is significantly expanded with a cost-effective, highly sensitive piezoelectric impact sensor crafted from FS.

Sodium alginate/chitosan composite scaffold reinforced with biodegradable polyesters/gelatin nanofibers for cartilage tissue engineering

Cartilage repair remains a significant challenge in tissue engineering. The Sodium alginate/Chitosan hydrogel scaffold, fabricated from natural polymers, has the potential to promote tissue regeneration. However, its poor mechanical performance limits its application. Research has shown that integrating nanomaterials into three-dimensional network materials can significantly enhance mechanical properties, which is particularly important for osteochondral replacement scaffolds. In this study, biodegradable polylactic acid-glycolic acid copolymer/polycaprolactone/gelatin (PLGA/PCL/GEL) nanofibers were prepared via electrospinning and integrated as a reinforcing phase. This enhancement significantly improved the mechanical performance of the sodium alginate/chitosan hydrogel, achieving a maximum compressive modulus of 665 kPa and compressive stress of 342 kPa. Moreover, the inherent biocompatibility of the composite scaffold remained high. This work demonstrates the potential of nanofiber/hydrogel scaffolds, contributing to the development of safe and multifunctional materials for clinical application.

Borax Cross-Linked Acrylamide-Grafted Starch Self-Healing Hydrogels.

The biocompatibility and renewability of starch-based hydrogels have made them popular for applications across various sectors. Their tendency to incur damage after repeated use limits their effectiveness in practical applications. Improving the mechanical properties and self-healing of hydrogels simultaneously remains a challenge. This study introduces a new self-healing hydrogel, synthesized by grafting acrylamide onto starch using ceric ammonium nitrate (CAN) as an initiator, followed by borax cross-linking. We systematically examined how the starch-to-monomer ratio, borax concentration, and CAN concentration impact the grafting reactions and overall performance of the hydrogels. The addition of borax significantly reinforced the strength of the hydrogel; the maximum storage modulus increased by 1.8 times. Thanks to dynamic borate ester and hydrogen bonding, the hydrogel demonstrated remarkable recovery properties and responsiveness to temperature. We expect that the present research could broaden the application of starch-based hydrogels in agriculture, sensors, and wastewater treatment.

Mechanics-Switchable and Antiswelling Colloidal Hydrogels Inspired by the Cononsolvency Effect.

Stiffness switching hydrogels have been in high demand for intelligent devices, adhesion science, soft robotics, and flexible electronics. However, it is challenging to post-tune the mechanical properties of a hydrogel once the polymer network structure is formed. Inspired by the cononsolvency effect, we prepared a mechanics-switching colloidal hydrogel through the precipitation polymerization of methacrylamide in mixed dimethyl sulfoxide and water solvents. The colloidal network enables the hydrogels to simultaneously strengthen, stiffen, and toughen. The colloidal hydrogels not only display a broad spectrum of adjustable mechanical properties (ranging from 0.08 to 57.1 MPa) via solvent response but also accomplish reversible stiffness conversion through the solvent-tuned conformational adjustment of colloidal polymer networks, with the maximum modulus conversion reaching 1427, and exhibit solvent-responsive shape memory. Based on the stable and tight colloidal network, the hydrogels exhibit antiswelling properties in various aqueous solutions and solvents. The colloidal hydrogel would provide more possibilities in various applications, such as antiimpact protection, shape memory, electronic switches, and intelligent engineering materials. It is envisioned that this work will provide key opportunities in developing mechanics-switching and on-demand tuning of soft materials for tissue engineering, flexible electronics, and biomedical science.

Enhanced ablation resistance and mechanical behavior of spark plasma sintered ZrB2-SiC composites with TiC addition

The study evaluated the ablation resistance and mechanical behavior of spark plasma sintered ZrB2-25 vol% SiC-TiC (5–15 vol%) composites. The addition of TiC improved ablation resistance by promoting the formation of ZrO2.TiO2 and TiO2 phases on the oxidized composites. The ZrB2-25 vol% SiC-15 vol% TiC composite exhibited the lowest mass ablation rate of 0.11 mg/s and maximum fracture toughness of 5.8±0.29 MPa.m0.5. After ablation, SiC particle pull-out, crack deflection and crack bridging were identified as the primary toughening mechanisms. The maximum microhardness of 23.01±1.18 GPa and compressive strength of 1688.2±75.5 MPa were obtained for the ZrB2-25 vol% SiC-10 vol% TiC composite, which correspond to 92.86 % and 94.31 % of their respective maximum values prior to ablation. Furthermore, nanoindentation studies revealed significant improvements in both elastic modulus and nanohardness with the addition of TiC due to reduction in porosity and refinement in SiC grain size. After ablation, the elastic modulus and nanohardness reduced. However, the ZrB2-25 vol% SiC-10 vol% TiC composite retained a maximum elastic modulus of 433.61 GPa and nano-hardness of 21.88 GPa. The oxidation behavior of ZrB2-SiC composites containing TiC was analyzed at 1500°C for 6 hours in air. The TiC-containing composite exhibited lower mass gain, lower parabolic oxidation rate constant and a thin oxide layer compared to the ZrB2-SiC composites.

Extremal spectral radii of uniform supertrees

For a hypergraph $\mathcal{G}=(V, E)$ consisting of a nonempty vertex set $V=V(\mathcal{G})$ and an edge set $E=E(\mathcal{G})$, its adjacency matrix $\mathcal {A}_{\mathcal{G}}=[(\mathcal {A}_{\mathcal{G}})_{ij}]$ is defined as $(\mathcal {A}_{\mathcal{G}})_{ij}=\sum_{e\in E_{ij}}\frac{1}{|e| - 1}$, where $E_{ij} = \{e \in E : i, j \in e\}$. The spectral radius of a hypergraph $\mathcal{G}$, denoted by $\rho(\mathcal {G})$, is the maximum modulus among all eigenvalues of $\mathcal {A}_{\mathcal{G}}$. In this paper, we represent some results on the spectral radius changing under some graphic structural perturbations. With these results, among all $k$-uniform ($k\geq 3$) supertrees with fixed number of vertices, the supertrees with the maximum, the second maximum, and the minimum spectral radius are completely determined, respectively.

A novel thermoplastic material: Pre‐polymerized PMMA liquid resin and continuous glass fiber‐reinforced composite initiated by benzoyl peroxide/N,N‐dimethylaniline

AbstractThermoplastic PMMA was rarely exploited in continuous fiber‐reinforced composites due to its viscous high‐temperature molten fluid as well as pessimistic wettability into fiber fabric. Redox‐active polymerization is a green route to develop a new liquid PMMA resin at room temperature to provide an in situ curing with the advantages of energy saving and consumption reduction. In this paper, BPO/DMA was adopted as a redox initiator pair, and the effect of MMA:BPO:DMA ratio on curing time, Mn, Tg, and mechanical properties of PMMA were systematically studied. When the ratio of MMA:BPO:DMA is 200:1.2:1, PMMA‐200 achieved optimistic mechanical properties at 20°C (tensile strength, 64.7 MPa; tensile modulus, 3352 MPa; bending strength, 125.3 MPa; bending modulus, 3023 MPa). Moreover, the mechanical properties were further improved at low temperatures. The maximum tensile strength and tensile modulus were up to 97.43 and 4297 MPa (−40°C) respectively. The tensile strength (0°, 1103 MPa; 90°, 52.3 MPa) and tensile modulus (0°, 47.5 GPa; 90°, 14.2 GPa) of glass‐fiber‐reinforced PMMA composite at 20°C were found to be comparable with epoxy resin‐based composites and even higher at lower temperature. In summary, redox‐initiated PMMA and its fiber‐reinforced composites are promising thermoplastic materials as new lightweight alternatives.Highlights Preparation method of PMMA resin and glass fiber composite. Research on the mechanical properties, molecular weight, glass transition temperature, curing time, etc. of PMMA resin. Testing of mechanical properties of PMMA glass fiber composites at room temperature and low temperature. Current applications and prospects of PMMA glass fiber composites.

Surface Engineering of Polymeric Colloidal Crystals by Temperature - Pressure Annealing.

Polymer colloidal crystals (PCCs) have been widely explored as acoustic and optical metamaterials and as templates for nanolithography. However, fabrication impurities and fragility of the self-assembled structures are critical bottlenecks for the device's efficiency and applications. We have demonstrated that temperature-assisted pressure [ annealing results in the mechanical strengthening of PCCs, which improves with the annealing temperature. Here, the enhancement of elastic properties and morphological features of self-assembled PCC's is evaluated using Brillouin light scattering and scanning electron microscopy. The pressure-induced effects on the vibrational modes of PCCs are also illustrated at temperatures well below the polymer glass transition. While the PCCs colloid constituents display reversibility, the PCC material is strongly irreversible in the performed thermodynamic cycle. The effective elastic modulus enhances from 0.7GPa for the pristine sample to 0.8GPa, solely by pressure annealing at room temperature. [ annealing at higher temperatures leads to a maximum effective elastic modulus of 1.7GPa, more than twice the value in the pristine sample. Above a cross-over pressure, 725bar at 348K), the PCCs respond elastically and, hence, reversibly to pressure changes.