Bulk Modulus Research Articles

Wet chemical synthesis of nanohydroxyapatite within poly(sodium sulfonated butylene fumarate‐co‐acrylic acid) as bone scaffold: effects of sulfonate and carboxylic acid groups

AbstractThis study investigates the synthesis, nucleation and modification of biodegradable poly(sodium sulfonated butylene fumarate‐co‐acrylic acid)/hydroxyapatite nanocomposite scaffolds for bone tissue engineering, with a focus on the effects of incorporating hydrophilic sulfonate and carboxylic acid groups. Poly(butylene fumarate) was sulfonated at varying degrees and used to form nanocomposites through in situ nucleation of nanohydroxyapatite (nHA) in a simulated body fluid solution. Critical parameters such as water absorption, swelling behavior, mechanical properties, nanoparticle dispersion and biocompatibility were evaluated. Water uptake ratios ranged from 2.72 to 6.88 g g−1, while compressive modulus values increased up to 25.9 times compared with the corresponding homopolymers, demonstrating improved mechanical stability. Despite the formation of over 80% nanoparticles, well‐distributed nHA, with sizes averaging 39 ± 13 nm, was achieved through the incorporation of sulfonated groups, preventing nanoparticle agglomeration within the scaffold matrix. Additionally, the scaffolds supported human dermal fibroblast adhesion and proliferation, with cell viability remaining high throughout the culture period. These results suggest that the developed nanocomposite scaffolds offer enhanced biocompatibility, mechanical strength and osteogenic potential, making them promising candidates for bone tissue regeneration applications. © 2024 Society of Chemical Industry.

Efficiency of in-wall weave patterns on the mechanical properties of integrally woven carbon/carbon honeycomb structures

Combining honeycomb structures with carbon/carbon (C/C) composites provides significant benefits, such as enhanced load-bearing strength, reduced weight, minimal thermal expansion, and no moisture absorption. These characteristics make such structures particularly suited for space applications. Carbon fiber reinforced composites, with their versatile design capabilities, emerge as an ideal material for satellite bearing platforms. In this study, three continuous carbon fiber woven structures are designed, and an integrally woven ortho-hexagonal C/C honeycomb structure was fabricated through performing Chemical Vapor Infiltration (CVI) process on honeycomb preform. A multiscale damage model is used to analyze and compare the properties related to out-of-plane compression, shear in the L-direction, and shear in the W-direction across these three C/C honeycomb structures. Results indicate that the plain-woven C/C honeycomb structure demonstrates the most favorable mechanical properties, with the highest compressive modulus and shear strength under various loading conditions. Damage initially occurred in single-layer honeycomb walls with void defects, with ultimate failure appearing predominantly in the middle regions of all walls. These findings establish the plain-woven structure as the preferred choice for satellite bearing platforms due to its outstanding mechanical characteristics, providing stability and strength crucial for space applications.

Poroelasticity and rock-physics templates

Two common rock-physics templates that are used to identify the geologic facies and fluid trends derived from well log or prestack inverted seismic data involve crossplotting the [Formula: see text]/[Formula: see text] ratio against acoustic impedance, [Formula: see text] (the product of P-wave velocity [Formula: see text] and density [Formula: see text]) and [Formula: see text] against [Formula: see text], wherein [Formula: see text] and [Formula: see text] are the Lamé coefficients extracted from the P- and S-wave velocity, called the LambdaMuRho (LMR) method. Using well-log examples from an Alberta gas well and a deeper North Sea oil well, we show how to superimpose the constant [Formula: see text] and [Formula: see text] curves on a [Formula: see text]/[Formula: see text] versus [Formula: see text] crossplot, which produce the orthogonal trends of stiffness or porosity (from [Formula: see text]) and fluid saturation (from [Formula: see text]) that match the data trends reasonably well. We then consider the related technique of KMuRho (KMR), wherein K represents the bulk modulus and show how to superimpose the constant [Formula: see text] trends on a [Formula: see text]/[Formula: see text] versus [Formula: see text] crossplot. Again, we obtain the orthogonal trends of stiffness or porosity (from [Formula: see text]) and fluid saturation (from [Formula: see text]), but the fit to our real data examples is less accurate than with LMR. Using the Biot-Gassmann poroelasticity theory, we generalize the LMR and KMR approaches into a technique we call FluidMuRho (FMR). In the FMR techniques, we introduce two new fitting parameters, f and d, wherein f is a fluid term derived from the Biot-Gassmann theory, and d is the dry rock [Formula: see text]/[Formula: see text] ratio squared. When we superimpose the fluid trends from the FMR technique on our two well-log data sets and adjust the f and d parameters, we achieve accurate fits to the data sets. Finally, we apply the FMR technique to a seismic case study from the Gulf of Mexico. In an appendix, we compare the FMR technique to the empirical curved pseudo-elastic impedance and pseudo-elastic impedance for lithology methods.

Deep reinforcement learning for inverse inorganic materials design

A major obstacle to the realization of novel inorganic materials with desirable properties is efficient materials discovery over both the materials property and synthesis spaces. In this work, we propose and compare two novel reinforcement learning (RL) approaches to inverse inorganic oxide materials design to target promising compounds using specified property and synthesis objectives. Our models successfully learn chemical guidelines such as negative formation energy, charge neutrality, and electronegativity balance while maintaining high chemical diversity and uniqueness. We demonstrate multi-objective RL algorithms that can generate novel compounds with both desirable materials properties (band gap, formation energy, bulk modulus, shear modulus) and synthesis objectives (low sintering and calcination temperatures). We apply template-based crystal structure prediction to suggest feasible crystal structure matches for target inorganic compositions identified by our machine learning (ML) algorithms to highlight the plausibility of the identified target compositions. We analyze the benefits and drawbacks of the ML approaches tested in this work in the context of accelerated inorganic materials design. This work isolates and evaluates the effects of different RL methodologies to suggest promising, valid compounds of interest by exploring the chemical design space for materials discovery.

Construction and Experimental Validation of Embedded Potential Functions for Ta-Re Alloys.

Ta/Re layered composite material is a high-temperature material composed of the refractory metal tantalum (Ta) as the matrix and high-melting-point, high-strength rhenium (Re) as the reinforcement layer. It holds significant potential for application in aerospace engine nozzles. Developing the Ta/Re potential function is crucial for understanding the diffusion behavior at the Ta/Re interface and elucidating the high-temperature strengthening and toughening mechanism of Ta/Re layered composites. In this paper, the embedded atom method (EAM) potential function for tantalum/rhenium binary alloys (Ta-Re alloys) is derived using the force-matching method and validated through first-principles calculations and experimental characterization. The results show that for the lattice constant of a bcc structure containing 54 atoms, surface formation energies per unit area of Ta-Re alloys obtained based on the potential function are 12.196 Å, E100 = 0.16 × 10-2 eV, E110 = 0.10 × 10-2 eV, and E111 = 0.08 × 10-2 eV, with error values of 0.015 Å, 0.04 × 10-2 eV, 0.02 × 10-2 eV, and 0.01 × 10-2 eV, respectively, compared with the calculations from first principles calculations. It is noteworthy that the errors in the average binding energies of Ta-rich (Ta39Re20, where the number of Ta atoms is 39 and Re atoms is 20) and Re-rich (Ta20Re39, where the number of Ta atoms is 20 and Re atoms is 39) cluster atoms, calculated by the potential function and first-principles methods, are only 1.64% to 1.98%. These results demonstrate the accuracy of the constructed EAM potential function. Based on this, three compositions of Ta-Re alloys (Ta48Re6, Ta30Re24, and Ta6Re48; the numerical subscripts represent the number of atoms of each corresponding element) were randomly synthesized, and a comparative analysis of their bulk moduli was conducted. The results revealed that the experimental values of the bulk modulus showed a decreasing and then an increasing tendency with the calculated values, which indicated that the potential function has a very good generalization ability. This study can provide theoretical guidance for the modulation of Ta/Re laminate composite properties.

Elastic properties of rock salt ScN thin films investigated by laser ultrasound

Elastic moduli of scandium nitride (ScN) films are determined using a laser-based experimental method working with surface acoustic waves (SAWs). ScN, a semiconductor material with promising potential for various applications, crystallizes in the cubic rock salt (rs) structure. We investigate two samples of high-crystallinity ScN(111) films with thicknesses ∼200 and ∼300 nm, grown on Si(111) substrates by pulsed DC-magnetron co-sputtering and a sample with a fiber-textured ScN film (∼800 nm) on Si(001). From the shape evolution of laser-generated acoustic pulses, SAW dispersion curves were obtained in a frequency range of 50–500 MHz. In order to take advantage of the anisotropy of the film and substrate materials, measurements were performed for 10–15 SAW wavevector directions, which could be defined with a precision of 0.2°. Using perturbation theory with respect to the ratio of film thickness and SAW wavelength, two combinations of the three independent elastic constants of the high-crystallinity rs ScN films could be extracted from the measurement data. The surface roughness of the ScN films is accounted for with a simple model. Complete sets of the three elastic moduli were inferred in two different ways: (i) SAW dispersion data for the third sample were included in the extraction procedure; and (ii) the bulk modulus is set equal to a theoretical literature value. The extracted values for the three elastic constants are at variance with published theoretical results for single-crystal ScN. Possible reasons for these discrepancies are discussed.

Relationship Between the Carbonation Depth and Microstructure of Concrete Under Freeze-Thaw Conditions.

Concrete structures in cold regions are affected by freeze-thaw cycles (FTCs) and carbonation, which lead to the premature failure of concrete structures. The carbonation depth, relative dynamic elastic modulus (RDEM), compressive strength, porosity, and pore size distribution of concrete under FTC conditions were tested through an accelerated carbonation experiment to study the carbonation performance evolution. The freeze-thaw effect mechanism on concrete carbonation was further analyzed via the obtained relationship between carbonation depth and pore structure. The results showed that the FTC, as a powerful source of concrete damage, accelerates the carbonation reaction. Carbonization products fill some microcracks caused by the freeze-thaw process, improve the compressive strength and dynamic elastic modulus, and alleviate the damage to concrete caused by the FTC. After carbonization under freeze-thaw damage conditions, the content of macropores with d > 1000 nm decreases, while the content of transition pores with d ≤ 10 nm increases, which is the direct reason for the decrease in porosity and the improvement in strength. Therefore, the carbonation durability of concrete under freeze-thaw conditions can be improved by controlling the content of macropores with d > 1000 nm and increasing the content of transition pores with a pore size of 10 nm ≤ d < 100 nm. In addition, the relationship between carbonation depth and pore structure under freeze-thaw conditions was established, and the research results can provide a reference for the study of the carbonation performance of concrete under freeze-thaw conditions.

Modeling and numerical analysis of concrete specimen under dynamic and thermal loading taking into account non-linearity

In this study, we propose a model describing the mechanical behavior of basalt aggregate concrete under high temperatures. Basalt aggregate concrete is formulated. The bulk density, residual mechanical (compressive strength, tensile strength and elastic modulus) and microscopic properties of basalt aggregate concrete specimens are analyzed. The damage basalt aggregate concrete, the geometry and nonlinear behavior of the material is investigated. Based on Newton’s second law, the investigation is conducted on the simultaneous effects of mechanical loading and thermal treatment. The finite difference method is used for the numerical solution of the problem to determine the peak stress and strain of normal basalt aggregate concrete as a function of temperatures and time. It follows from the results obtained that, after [3–5 min] the critical temperature at which material damage, for both stress and strain, is observed to be 350 °C at the center, corresponding to a 30% reduction in peak stress on the value initially obtained experimentally; And 300 °C at the free and fixed end of basalt aggregate concrete specimen respectively, corresponding to a 38 and 30% reduction in stress in the z-axis direction. Beyond these temperatures, it is observed that the amplitude of the deformations continues to increase whatever the position announcing an imminent collapse of the material, probably due to the loss of stiffness of the cement paste which significantly reduces the mechanical performance of the normal basalt aggregate concrete observed experimentally.

Residual reliability of a composite material subjected to buckling and post-buckling tests: the case of reinforced concrete

This article examines the residual reliability of composite materials, focusing on reinforced concrete subjected to buckling and post-buckling tests, a crucial topic in civil engineering. The main aim of the study is to assess how these loads affect mechanical properties, including compressive strength and elongation at break, while identifying associated failure mechanisms. A rigorous methodology was adopted, involving experimental tests on reinforced concrete samples, followed by microscopic analysis and comparison with literature data. The results reveal a significant decrease in compressive strength and modulus of elasticity with increasing loads and loading cycles. In addition, the study highlights a reduction in elongation at break, indicating a loss of ductility and stiffness of the material. Failure mechanisms observed include cracking and delamination, suggesting that the residual reliability of reinforced concrete is inferior to that of advanced composites. These findings underline the importance of appropriate design to ensure the durability of reinforced concrete structures, taking into account the impact of extreme loads and environmental conditions. This research contributes to a better understanding of the behavior of composite materials under critical conditions, providing recommendations for improving design and construction practices in civil engineering.

First Principle Analysis on Elastic and Mechanical Behavior of High-Pressure Hexagonal MgZn2 Phase

There is a paucity of previous related studies exploring hexagonal MgZn2 in high-pressure environments. This study systematically analyzes the mechanical behavior of MgZn2 hexagonal alloys under high-pressure conditions using first principle calculations, bridging the gap in research in this area in the field. The results reveal that, with increasing pressure, the crystallite spacing (a/a0,c/c0) and ratio of volumes (V/V0) decrease significantly, indicating the structural condensation of the material under high pressure. Elastic constant analysis showed a notable enhancement in all constants, except for C13. Among them, C11 increased from 87.399 GPa to 311.45 GPa, and C33 increased from 135.279 GPa to 341.739 GPa, showing a faster growth rate, suggesting improved tensile strength in the material along the tensile direction. Mechanical stability assessments confirmed that the alloy remains stable over the 0 to 30 GPa pressure range. Further material characterization indicated that Poisson’s ratio remained above 0.26 at pressures from 0 to 30 GPa, suggesting excellent ductility and agreeing with the ratio of the shear modulus to the bulk modulus. As the pressure increases, both the hardness and sound velocity of MgZn2 increase, while the degree of anisotropy decreases. The present work gives important insights on the mechanical behavior of MgZn2 under high pressure, contributing to its application and property optimization.

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(&amp;epsilon;-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,&amp;nbsp; 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.

A comprehensive DFT study of the effect of the pressure on the structural, stability, electronic, optical, and mechanical properties of cubic RbSrI3

Abstract This study examines the structural, electrical, optical, and mechanical effects of hydrostatic pressure on cubic I-II-halide perovskite RbSrI3. The exchange–correlation term of the Khon-Sham equation is expressed using PBE-GGA. For all calculations, QuantumESPRESSO is used. PBE-GGA and pseudopotentials have been employed for ion-valence interaction. Under hydrostatic pressure, the lattice parameter a dropped from 6.34 Å. The structure is thermodynamically stable since the formation energy E f is negative and lowers as the negativity falls until pressure 31 GPa, when it becomes positive. This material depicts the transition from an indirect band gap at ambient pressure to a direct band gap that accelerates electron valence-to-conduction band transition. The band gap rises to 7 GPa, then falls to 1.49 eV at 50 GPa. The PDOS explains that the states that contribute to creating VBM and CBM changes in overlapping status and value which leads to such behavior of electronic nature. Optical properties show a stronger response at 50 GPa pressure, with ε 1 ( ω ) and ε 2 ( ω ) exhibiting similar behavior and a maximum value of nearly 10. However, ε 1 ( ω ) peaks in the visible light zone, while ε 2 ( ω ) peaks in the ultraviolet zone. This means the material absorbs and retains visible and ultraviolet radiation at its optimal level. Mechanical and elastic parameters were determined using finite strain theory. Born stability confirms mechanical stability since C 11 , C 44 , C 11 − C 12 , and C 11 + 2 C 12 have positive values and remain positive as pressure increases. Elastic moduli such bulk modulus ( B ), shear modulus ( G ), and Young’s modulus ( E ) indicate moderate hardness and resistance to pressure. Additionally, Poisson’s ratio ( υ ), Pugh’s ratio, and Cauchy pressure ( σ ) indicate ductility at ambient pressure, since they align with boundary values of υ (0.2959 &gt; 0.26), σ (0.92) (positive), and B / G (2.23 &gt; 1.75) (at ambient pressure). Increased pressure enhances ductility.

Ab Initio Investigation of the Mechanics and Thermodynamics of the Cubic EuAlO3 and GdAlO3 Perovskites for Optoelectronic Applications

Perovskites are currently becoming common in the field of optoelectronics, owing to their promising properties such as electrical, optical, thermoelectric, and electronic. Although mechanical and thermal properties also play a crucial part in the functioning of the optoelectronic devices, they have scarcely been explored. The present work performed an ab initio study of the mechanical and thermal properties of the cubic EuAlO3 and GdAlO3 perovskites for the first time using density functional theory. Quantum Espresso and Themo_pw codes were utilized by employing the generalized gradient approximation. Although the results showed that both materials have good mechanical and thermal properties that are ideal for the above–mentioned applications, EuAlO3 possessed better structural and thermal stability, bulk modulus, Poisson ratio, thermal expansion coefficient, and thermal stress; while GdAlO3 possessed better Young’s modulus and shear modulus. Moreover, the mechanical properties of the two materials turned out to be much better than those of the common materials for optoelectronic applications, while their thermal properties were comparable to that of sapphire glass. Since this study was computational, an experimental verification of the computed properties of the two materials needs to be carried out before they can be commercialized.

Use of Ultrasound to Identify Microstructure-Property Relationships in (AlN + WC) Fabricated with Electroless Ni Producing

In order to improve the properties of the materials produced by the powder metallurgy method, first of all, powders (16.59% AlN + 6.63% WC) were coated with nickel (Ni) by electroless method, and then box boriding, which is one of the most widely used surface coating methods, was applied. A composite formed with (16.59% AlN + 6.63% WC)76.7Ni was prepared under the Ar shroud in the temperature range of 1000-1400°C. Pulse-echo technique was used for ultrasonic velocity measurements on Ni coated (16.59% AlN + 6.63% WC) samples. It is aimed to examine the change of physical, mechanical and ultrasonic properties of the obtained ceramic-metal composites depending on different sintering temperatures. In addition, the samples were characterized by mechanical and metallographic examination. The results show that the longitudinal and transverse ultrasonic velocity values and ultrasonic modulus (shear, bulk, Young’s etc.) values increase simultaneously with the increase of sintering temperature. The highest microhardness value was observed in composite samples sintered at 1400°C and its value was 1150.80 Hv. The increased strength is mainly due to grain refinement and strong interfacial bonding between Ni particles and AlN and WC matrix.

Effect of Indenter Angle on Bearing Performance of Coal and Accompanying Rocks Under Point Load and Characterization of Mechanical Parameters

ABSTRACTCoal, mudstone, sandstone, and limestone, which are common in coal mines, were selected as research objects, and 60°, 90°, and 120° indenters were used to conduct point load tests to study the deformation and failure laws of rocks under point loads. This study identified a process for generating and crushing compacted bodies. As the indenter angle increased, the number of compacted bodies formed decreased significantly, and the stress drop decreased. The ultimate invasion depth upon reaching the failure load decreased as a quadratic function as the indenter angle increased. Under the load of indenter points at different angles, all samples underwent splitting failure along the loading axis. As the indenter angle increased, the indentation diameter increased quadratically. The angle of the indenter had a greater influence on the indentation diameter of low‐strength rocks, and the failure of coal and accompanying rocks was more stable under the action of large‐angle indenters. The point load test data were statistically analyzed. The load intensity of the indenter point at different angles exhibited a linear relationship with the uniaxial compressive strength, tensile strength, and elastic modulus, and the fitting degree was the best when the indenter angle was 120°

Construction of a Molecular Dynamics Model of N-A-S-H Geopolymer Based on XRD Analysis.

A geopolymer is a low-carbon cementitious material, and its condensation process is akin to the formation of inorganic polymers. The crystal phase of synthesized geopolymers was identified using XRD; the scattering peaks of amorphous phases were analyzed, and the zeolite minerals akin to different n(Si)/n(Al) geopolymers were determined. Based on this, a model structure of N-A-S-H geopolymers was established. The molecular dynamics structure of the model was simulated, and the density, energy, and bulk modulus of the model were calculated using three different force fields. According to the calculation results, the most suitable force field for N-A-S-H calculation is COMPASS III. In this study, all calculations were performed using MaterialsStudio 7.0. The research process introduces a new modeling method for geopolymers, similar to building C-S-H based on Tobermorite, which aids in advancing the molecular dynamics simulation of geopolymers.

First-principles calculations of the effect of vacancy defects on the optoelectronic and mechanical properties of the double perovskite Cs2NaInCl6

Abstract Cs2NaInCl6 have become a hot research topic in perovskite optoelectronic materials. However, there is no research on the vacancy properties of Cs2NaInCl6 at present. Herein，using density functional theory-based first-principles calculations, the impact of Cs, Na, In, and Cl single vacancies on the microstructure, electronic, optical, and mechanical properties of the double perovskite Cs2NaInCl6 were investigated. The research shows that the presence of vacancy defects leads to distortion of the Cs2NaInCl6 double perovskite structure and an increase in the unit cell volume. Cs vacancy (VCs) and Na vacancy (VNa) cause an increased band gap for Cs2NaInCl6, by 2.92eV and 3.1eV respectively, without changing the characteristics of the initial direct band gap; VIn and VCl cause the intrinsic semiconductor Cs2NaInCl6 to transform into p-type and n-type semiconductors, respectively, altering the conductivity of Cs2NaInCl6. In terms of optical properties, different vacancy defect systems exhibit different absorption abilities in the visible and ultraviolet light ranges. The defect system overall improves light absorption in the low energy region, and as the incident photon energy increases, the material exhibits the best optical performance at around 15eV. In addition, it is found that VCs, VNa, and VIn caused blue shift in the absorption edge of Cs2NaInCl6, while VCl caused red shift in the absorption edge. In terms of mechanical properties, defects cause varying degrees of reduction in Young's modulus (E), shear modulus (G), and bulk modulus (B) of Cs2NaInCl6, which to some extent alters the mechanical properties of Cs2NaInCl6. These research results provide theoretical guidance for understanding the influence of vacancies on the properties of Cs2NaInCl6 double perovskite and optimizing the performance of perovskite optoelectronic devices, and they also enhance its applications in photovoltaic cells, optoelectronic sensors, and other optoelectronic coupling devices.&amp;#xD;

Longitudinal Shear in Timber-Concrete Composites with Flexible Adhesive Connections-Experimental and Numerical Investigations.

Timber-concrete composites are established structural elements to combine the advantageous properties of both materials by connecting them. In this work, an innovative flexible adhesive connection in different configurations is investigated. Load-bearing capacity, stiffness, and the failure modes were first experimentally investigated by performing push-out tests. Subsequently, a numerical evaluation using ABAQUS 2017/Standard software was carried out in order to develop a three-dimensional numerical model. The Cohesive Zone Model (CZM) is employed to represent the adhesive characteristics at the contact areas between the Cross-Laminated Timber (CLT) and concrete elements. Three different connection configurations were evaluated, each consisting of five push-out specimens. The study investigates the impact of bonding surface area and the alignment of prefabricated glue strips with the load direction on the connection's longitudinal shear load-bearing capacity, stiffness, and slip modulus. In addition, the impact of cyclic loads and the impact of time on displacements were analyzed. The average load capacity of the full surface connection (type A) is 44.5% and 46.2% higher than the vertical adhesive strips (type B) and the horizontal adhesive strips (type C), respectively. However, the initial stiffness of the tested joints depends on the orientation of the prefabricated adhesive fasteners, being approximately 20% higher when the bonding elements are aligned parallel to the load direction compared to when they are oriented perpendicularly.

Nanoarchitectonics and Simulation on the Molecular-Level Interactions between p-Sulfonic Acid Calix[4]arene and Langmuir Monolayers Representing Healthy and Cancerous Cell Membranes.

The design of chemotherapeutic drug carriers requires precise information on their interaction with the plasma membrane since the carriers should be internalized by cells without disrupting or compromising the overall integrity of the membrane. In this study, we employ Langmuir monolayers mimicking the outer leaflet of plasma membranes of healthy and cancerous cells to determine the molecular-level interactions with a water-soluble calixarene derivative, p-sulfonic acid calix[4]arene (SCX4), which is promising as drug carrier. The cancer membrane models comprised either 40% 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 30% cholesterol (Chol), 20% 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE), and 10% 1,2-dipalmitoyl-sn-glycero-3-phospho-l-serine (DPPS). The healthy membrane models were composed of 60% DPPC or DOPC, 30% Chol, and 10% DPPE. SCX4 expanded the surface pressure isotherms and decreased compressional moduli in all membrane models, altering their morphologies as seen in Brewster angle microscopy images. A combination of polarization-modulated infrared reflection absorption spectroscopy and molecular dynamics simulations revealed that SCX4 interacts preferentially with lipid headgroups in cancer membrane models through electrostatic interactions with the amine groups of DPPS and DPPE. In healthy membrane models, SCX4 interacts mostly with cholesterol through van der Waals forces. Using a multidimensional projection technique to compare data from the distinct membrane models, we observed that SCX4 effects depend on membrane composition with no preference for cancer or healthy membrane models, which is consistent with its biocompatibility. Furthermore, the interactions and close location of SCX4 to the headgroups indicate that it does not compromise membrane integrity, confirming that SCX4 may be a suitable drug carrier.

Effect of Variations of Amine Content and Network Branching on Thermomechanical Properties of Epoxy Systems.

In thermosetting epoxies, thermomechanical properties can be enhanced by conscious selection of curing agents. Full cross-linking leads to a maximum in the glass- transition temperature. However, the relation between the glass transition temperature and the epoxy matrix depends on several factors beyond the cross-linking degree, such as the molecular weight of the polymers, network organization, amount of branching, and the presence of hydrogen bonds. In this study, we investigated adding non- stoichiometric ratios of the epoxy resin Epikote 828 and the curing agent Jeffamine D230. The investigations were done through a combination of molecular dynamics simulations and experiments, primarily differential scanning calorimetry and nanoindentation. Reorganization of the network to fewer clusters with a higher degree of linearity overcomes the effect of cross-linking and leads to a reduction of glass-transition temperature with increasing concentrations of curing agent to epoxy. The elastic, shear, and compressive moduli remained constant. Hence, moderating the curing agent con- tent has the potential to improve thermal properties while maintaining mechanical properties for this epoxy system.