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The purpose of this study is to evaluate the effects of glass fiber (GF) of PA66-GF30 orientation on very high cycle fatigue (HVCF) life and also to develop an optimized test apparatus such as measurement of dynamic elastic modulus and design of test specimens. Dynamic elastic modulus, tensile strength and fatigue strength tests were conducted at room temperature based on GF orientation (0°, 45°, 90°). Conventional fatigue (3 Hz) and ultrasonic fatigue (20 kHz) tests were performed at the same stress ratio (R = −1). Fracture surface observation showed that GF 0° exhibited a higher fatigue strength in comparison with GF 45 and 90°. Various defects such as voids and microcracks to the load direction around the GF end or debonding in glass fiber reinforced plastic (GFRP) and the slope change in very long life regime of S –N diagram. [ABSTRACT FROM AUTHOR]

The development of dental restorative materials that mimic tooth-like properties provided by graded structures, aesthetics and properties such as strength, damping capacity and the ability for a continuous remodeling according to the biomechanical solicitation is a great challenge. In this work, damping capacity and dynamic Young's modulus of Y-TZP/porcelain composites for all-ceramic dental restorations were studied. These mechanical properties were assessed by dynamic mechanical analyses (DMA) at frequencies of 1, 5 and 10 Hz, over a temperature ranging from 0 to 60 °C, simulating extreme conditions when a cold or hot drink is experienced. The results showed that porcelain and porcelain-matrix composites exhibited higher damping capacity while Y-TZP and Y-TZP-matrix composites presented higher dynamic Young's modulus. Furthermore, while damping capacity is strongly influenced by the temperature, no significant difference in dynamic Young's modulus was found. For both damping and modulus properties, no significant influence of frequency was found for the tested materials. Based on the obtained results and also on the known advantages of the graded Y-TZP/porcelain structures over traditional bi-layer solutions (e.g., improved bending strength, enhanced mechanical and thermal stress distribution), a novel design of all-ceramic restoration with damping capacity has been proposed at the end of this study. A positive impact on the long-term performance of these all-ceramic restorations may be expected. Image 1 • Porcelain matrix composites exhibited higher damping capacity. • Zirconia-rich composites demonstrated higher dynamic Young's modulus. • Dynamic Young's modulus was not influenced by tested frequencies and temperature. • Different damping behaviors with increasing temperature were observed. • From results a novel bio-inspired design was proposed for all-ceramic restorations. [ABSTRACT FROM AUTHOR]

Abstract Conversely to natural teeth, where periodontal ligament (PDL) and pulp works as a damper reducing the effect of the stress on surrounding structures, when natural teeth is lost and replaced or restored the biting forces are directly transmitted to the bone or affect the integrity of the adjacent bottom layers. In this study, damping capacity and dynamic Young's modulus of CoCrMo-porcelain composites for dental restorations were evaluated. Dynamic Young's modulus and damping capacity of materials were assessed by dynamic mechanical analyzes (DMA) at 1 and 10 Hz frequencies, over a temperature ranging (18–60 °C). Results show that by reinforcing dental porcelain with metallic particles, producing ceramic matrix composites (CMCs) with 20 vol% and 40 vol% of metallic particles, the damping capacity and dynamic Young's modulus are improved. A decrease on both properties of the metal matrix composites (MMCs) with increasing ceramic particles content (from 20 vol% to 40 vol% of ceramic phase) was observed for all the studied frequencies and temperatures. While damping capacity is strongly dependent on frequency, no significant difference in dynamic Young's modulus was found. Results show that besides the yet reported advantages of the bio-inspired functionally graded restorations over traditional bilaminate ones, traduced by improved veneer to substrate adhesion and by the enhanced thermal and mechanical stress distribution, these restorations can also display improved behavior as regard to a damping capacity, which may have a positive impact in the long-term performance of implant – supported prosthesis. Graphical abstract fx1 Highlights • All CoCrMo-porcelain composites and monolithic materials were successfully produced by hot pressing technique. • Both damping capacity and dynamic Young's modulus are dependent on temperature. • A pronounced influence of frequency was not found in dynamic Young's modulus when compared with damping capacity. • From results it is possible to tailor local properties to mimic natural teeth by selecting different materials combination. • A bio-inspired FGM design is proposed for dental restoration. [ABSTRACT FROM AUTHOR]

Highlights • Ti 2 AlC significantly contributes to the damping capacity and to dynamic moduli of composites. • The formation of interfacial robust amorphous magnesium layer gives rise to the transformed tensile fracture mechanisms. • A high activation energies (H) of damping peaks for composites was calculated to 128 kJ/mol. Abstract The evolutions with the temperature of damping capacities and dynamic Young's moduli of ternary Ti 2 AlC particles reinforced AZ91D composites were investigated. This work has highlighted that Ti 2 AlC significantly contributes to the damping capacity and to dynamic moduli of composites. With increasing temperature, especially above 200°C, the interfacial damping capacity becomes dominant and dynamic moduli of composites decrease. These trends were revealed from the transformed tensile fracture mechanisms. At room temperature, Ti 2 AlC particles delaminated without any decohesion between Ti 2 AlC particles and the Mg matrix. However, the interfacial decohesion occurred above 200°C. One explanation of this change of decohesion mechanism could be ascribed to the inherent structure of the Ti 2 AlC MAX phase and to the formation of a robust amorphous magnesium layer at the interface between Ti 2 AlC and magnesium matrix that was evidenced by HRTEM. This amorphous layer further gives rise a high activation energies (H) of damping peaks for composites, which was calculated to 128 kJ/mol. This value is higher than those calculated for SiC or graphite reinforced AZ91D composites, making Ti 2 AlC particles particularly interesting for application in reinforcing magnesium composites. [ABSTRACT FROM AUTHOR]

In this paper, a new approach is proposed for coalbed methane (CBM) reservoir brittleness index ( BI ) calculations. The BI , as a guide for fracture area selection, is calculated by dynamic elastic parameters (dynamic Young's modulus E d and dynamic Poisson's ratio υ d ) obtained from an amplitude versus offset (AVO) simultaneous inversion. Among the three different classes of CBM reservoirs distinguished on the basis of brittleness in the theoretical part of this study, class I reservoirs with high BI values are identified as preferential target areas for fracturing. Therefore, we derive the AVO approximation equation expressed by E d and υ d first. This allows the direct inversion of the dynamic elastic parameters through the pre-stack AVO simultaneous inversion, which is based on Bayes' theorem. Thereafter, a test model with Gaussian white noise and a through-well seismic profile inversion is used to demonstrate the high reliability of the inversion parameters. Accordingly, the BI of a CBM reservoir section from the Qinshui Basin is calculated using the proposed method and a class I reservoir section detected through brittleness evaluation. From the outcome of this study, we believe the adoption of this new approach could act as a guide and reference for BI calculations and evaluations of CBM reservoirs. [ABSTRACT FROM AUTHOR]

This paper describes a method of determining the dynamic Young’s modulus of concrete by measuring the eigenfrequency. In the introduction, reference is made to the findings reported by other researchers in this field. As part of this study, laboratory tests on 24 beam elements (differing in their reinforcement ratios and concrete mixes) were carried out using operational modal analysis. The results of dynamic and static tests carried out on concrete cylinders are compared. Conclusions and recommendations concerning the determination of the dynamic Young’s modulus are formulated. [ABSTRACT FROM AUTHOR]

Objectives Flowable dental composites are used as restorative materials due to their excellent esthetics and rheology. However, they suffer from inferior mechanical properties compared to conventional composites. The aim of this study was to reinforce a flowable dental composite with TiO 2 nanotubes (n-TiO 2 ) and to assess the effect of n-TiO 2 surface modifications on the mechanical properties of the reinforced composite. Methods n-TiO 2 were synthesized using an alkaline hydrothermal process and then functionalized with silane or methacrylic acid (MA). Nanotubes were characterized by scanning and transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. Commercially available flowable composite (Filtek™ Supreme Ultra Flowable Restorative, 3M ESPE) was reinforced with varying amounts of nanotubes (0–5 wt%). Flowability of the resulting composites was evaluated using a Gillmore needle method. Dynamic Young's modulus ( E ) was measured using an ultrasonic technique. Fracture toughness ( K Ic ) was assessed using a notchless triangular prism and radiopacity was quantified. Viability of NIH/3T3 fibroblasts was evaluated following incubation on composite specimens for 24 h. Results Electron microscopy revealed a tubular morphology of n-TiO 2 . All reinforced composites exhibited significantly greater values of E than unreinforced composite. Composites reinforced with 3 wt% n-TiO 2 functionalized with MA exhibited the greatest values of E and K Ic . Cytotoxicity assays revealed that reinforced composites were biocompatible. Taken together, flowable composites reinforced with n-TiO 2 exhibited mechanical properties superior to those of unreinforced composite, with minimal effects on flowability and radiopacity. Significance n-TiO 2 -reinforced flowable composites are promising materials for use in dental restorations. [ABSTRACT FROM AUTHOR]

Lightweight metal-matrix composites (MMC) are being applied in many fields such as aerospace and automotive, where detailed knowledge about their elastic and inelastic properties is required to make optimal design of the component. In this study the high-temperature damping capacity and dynamic Young’s modulus of hot-pressed AlSi-based hybrid composites reinforced with silicon carbide particles (SiC p ) and carbon nanotubes (CNTs) were experimentally measured and compared with AlSi–SiC p and AlSi–CNT composites. Results show that by reinforcing AlSi–SiC p with CNTs, the damping capacity is improved without reducing mechanical properties. The highest damping capacity value was attained by AlSi–(CNT–SiC p ) hybrid composite, for all the studied frequencies and temperatures, followed by AlSi–SiC p and AlSi–CNT composites. The possible damping mechanisms for all these produced composites are presented and discussed. Unlike to damping capacity, the dynamic Young’s modulus shows no substantial changes after adding CNTs to AlSi–SiC p . Results show that by using a proper combination of materials (including different types of reinforcements), scales (nano- and micro-sized reinforcements) and manufacturing processes, the design of a material with required damping capacity and mechanical properties is possible. [ABSTRACT FROM AUTHOR]

Objectives: To synthesize and characterize machinable, bioactive glass-ceramics (GCs) suitable for dental implant applications. Methods: A glass in the SiO2–Al2O3–CaO–CaF2–K2O–B2O3–La2O3 system was synthesized by wet chemical methods, followed by calcination, melting and quenching. Crystallization kinetics were determined by differential thermal analysis (DTA). GC discs were produced by cold pressing of the glass powder and sintered using schedules determined by DTA. The crystalline phases and microstructure of GC samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Dynamic Young's modulus (E), true hardness (H o), fracture toughness (K IC) and brittleness index (BI) were evaluated. Bioactivity was studied by examining the formation of hydroxyapatite (HA) on the GC surfaces after soaking in simulated body fluid (SBF). Attachment and proliferation of MC3T3-E1 osteoblastic cells were assessed in vitro. Results: Miserite [KCa5(Si2O7)(Si6O15)(OH)F] was the main crystalline phase of the GC with additional secondary phases. Microstructural studies revealed interlocking lath-like crystalline morphology. E, H o, and K IC values for the GCs were 96±3GPa, 5.27±0.26GPa and 4.77±0.27MPam0.5, respectively. The BI was found to be 1.11±0.05μm−0.5, indicating outstanding machinability. An HA surface layer was formed on the GC surfaces when soaked in SBF, indicating potential bioactivity. MC3T3-E1 cells exhibited attachment, spreading and proliferation on GC surfaces, demonstrating excellent biocompatibility. Significance: We present a novel approach for the synthesis of miserite GC with the physical and biological properties required for non-metallic dental implant applications. [ABSTRACT FROM AUTHOR]

Abstract: Porous samples of commercially pure titanium (CP Ti) were fabricated by using sodium chloride (NaCl) as space-holder with percentages between 40 and 70vol%. The dissolution of NaCl in distilled water, the structural integrity of samples and the reproducibility of the procedure were studied as a step prior to sintering. All these parameters were evaluated in terms of the compaction pressure, temperature and agitation of water, and dissolution time. The characterization of samples included density, porosity and dynamic Young''s modulus. The results indicate that the most efficient lixiviation, according to the desired balance of properties, was by immersion in hot water, without agitation and for prolonged cycles of immersion time. [Copyright &y& Elsevier]

Abstract: Thermal effects on the vibrational behaviors and dynamic Young’s modulus of single-walled carbon nanotubes (SWCNTs) are investigated through both constant temperature molecular dynamics (MD) simulation and modified molecular structural mechanics (MMSM) modeling. The MD simulation incorporates a modified Nosé-Hoover thermostat model to control the system temperature. In the MMSM modeling, the covalent and nonbonded interactions between carbon atom pairs are modeled with the second generation force field and the Lennard–Jones potential, respectively, where the covalent bonds are treated as Euler–Bernoulli beam and the temperature-dependent bond length and angle are determined through the Badger’s rule and MD simulation. The results derived from these two approaches are compared with each other and the published theoretical and experimental data. Results show that the dynamic Young’s modulus of the SWCNTs tends to be smaller than the published static one obtained from uniaxial tensile tests, and their natural frequency and dynamic Young’s modulus would decrease with increasing temperature. Moreover, a comparable frequency ratio of the first two flexural modes is achieved by these two approaches. The frequency ratio is highly dependent on their aspect ratio but independent of temperature, and would converge to the literature experimental data (about 6.1–6.2) as the aspect ratio becomes very large. [Copyright &y& Elsevier]

Abstract: An experimental study was performed to evaluate the delamination in the concrete using ultrasonic pulse velocity (UPV) method. Two slab specimens of 150-mm and 300-mm thicknesses consisted of delaminations of varying sizes at quarter depths. Using indirect transmission method, the transit times of longitudinal and Rayleigh waves were measured to determine the dynamic Young’s modulus and Poisson’s ratio of the concrete. The static modulus was also measured and compared. The location and size of the delaminations in the slab were evaluated from the direct transmission method. The diffraction of the longitudinal wave at delaminations decreased the wave velocity and a qualitative correlation was established between the transit time of the UPV signal and the size of the delamination. [Copyright &y& Elsevier]

Abstract: The effects of Ta and Hf on the dynamic Young''s moduli and tensile properties of Ti–Ta and Ti–Hf alloys for biomedical applications are comparatively studied in this paper. It is found that with increasing Hf content, the dynamic Young''s modulus of the Ti–Hf alloy gently decreases and its tensile strength keeps on increasing. In contrast, with increasing Ta content, the dynamic Young''s modulus of the Ti–Ta alloys first decreases, reaches a minimum value of 69GPa and then increases. In parallel, the tensile strength first increases, reaches a maximum value of 587MPa, and then slightly decreases. It is shown that the addition of Hf has a slight influence on the dynamic Young''s modulus and a strong influence on the tensile properties of the Ti–Hf alloy, while an increase of Ta content has a strong effect on both the dynamic Young''s modulus and tensile properties of the Ti–Ta alloy. [Copyright &y& Elsevier]

• It is possible to pre-crack CTBM specimens in laboratory with a mechanical hammer. • Dynamic Young's modulus measurements through resonance testing are a great non destructive tool to evaluate the effect of the pre-cracking. • The pre-cracking of CTBM specimens does not change much the rate of water evaporation. • Pre-cracked CTBM specimens have slightly higher mechanical strengths than CTBM specimens without pre-cracking as soon as a few days after the pre-cracking. In this paper, the effects of pre-cracking on the early-age mechanical properties of a cement-treated base material (CTBM) were studied. To do so, CTBM with 4% cement by mass of dry granular material were mixed in laboratory in order to make cylindrical specimens. Half of the specimens were pre-cracked (PC) with a mechanical impact hammer after a two days moist curing process. The immediate effect of the pre-cracking (PC) was evaluated with dynamic Young's modulus measurements performed just before (B) and right after (A) the PC. Then, tests were performed in laboratory to compare the early-age mechanical properties (dynamic Young's modulus, compressive and indirect tensile strengths) of the specimens without pre-cracking (WPC) and with pre-cracking (PC). As early as five days after the pre-cracking, the dynamic Young's modulus, and the compressive and indirect tensile strengths of the PC specimens are higher than those of the WPC specimens. In addition, the pre-cracking seems to accelerate the hydration process and water evaporation. The results of this study therefore suggest that the pre-cracking only has a positive effect on the early increase of the mechanical strengths. [ABSTRACT FROM AUTHOR]

• A higher chemical shrinkage is seen in 60% recycled waste glass cement paste. • Increasing glass powder content lead to much more refinement of mortar microstructure. • Dynamic young and shear moduli decrease by increasing glass powder content. • Porosity and mass loss by evaporation increase by increasing glass powder content. This work deals with the characterization of the properties of mortars and cement pastes made with powdered soda lime waste glass. Different rates of cement replacement by weight are used: 0%, 10%, 25%, 35% and 60%. Both fresh and hardened properties are assessed. The influence of glass powder on the workability of mortar is determined using flow table tests. Chemical shrinkage and hydration heat of early age blended cement paste are evaluated using gravimetric methods and isothermal calorimetric respectively. The dynamic Young's and shear moduli of mortar are evaluated using nondestructive methods. Mechanical performances of mortars are measured using flexural and compressive strength tests. Pore structures of different mortars are investigated with mercury intrusion and water porosity tests. Results from this investigation indicate that the amount of cement replacement by glass powder plays a critical role in determining mortar characteristics. Chemical shrinkage and heat assessment show that high glass powder replacement of cement paste increases the hydration reaction rate. Compressive strength and dynamic Young's and shear moduli values decrease with increasing glass powder content especially for mortar made with 60% glass powder. Mortar made with 60% glass powder has bigger pores due to the dilution effect, i.e., the reduction in the amount of hydration product at 7 days hydration. Significant compressive strength is gained between 7 and 90 days for mortar with glass powder, especially with 60% replacement showing pozzolanic reaction taking place during this period. The pozzolanic reaction that occurs between glass powder and calcium hydroxide (Ca(OH) 2) to form more calcium silicate hydrate gel (C-S-H) leads to the refinement of pores and the reduction of porosity. [ABSTRACT FROM AUTHOR]

The microstructure evolution during aging heat treatment and its effects on the tensile properties and dynamic Young's modulus of a biomedical β titanium alloy Ti–10Mo–6Zr–4Sn–3Nb were investigated. The results demonstrated that a large amount of isothermal ω phase precipitated from the matrix after aging at a low temperature of 400 °C, and the formation mechanism of the ω phase was dominated by the collapse of the {222} plane collapse. With the increase of aging temperature, the ω phase was gradually replaced by α phase, and the morphology of the α phase changed from spherical to needle-like. Furthermore, the increase of the aging temperature accelerated the aging precipitation of the alloy. The results on the mechanical properties revealed that the presence of a large amount of isothermal ω phase can lead to a high dynamic Young's modulus of the alloy after aging at 400 °C, and cause the brittle fracture. The alloy composed of β+ω+α or β+α microstructures exhibited the higher strength and ductility, and lower dynamic Young's modulus than that composed of β+ω phase. The increase of the α phase content during aging at higher temperature, can lead to an significant enhancement of the dynamic Young's modulus. [ABSTRACT FROM AUTHOR]

• To assess the damage of concrete structure subjected to freeze-thawed effects. • A method to monitor AE energy activity of core samples under uniaxial compressive loading was investigated. • The degree of damage was visualized using X-ray CT images. • Quantification of concrete damage was analyzed relation between AE energy parameter and accumulation of cracks. As a detailed inspection of a concrete structure in service, core samples are usually drilled out and then mechanical properties are measured. In this study, damage estimation of freeze-thawed concrete from concrete-core samples is developed, applying acoustic emission (AE) method. By the authors, the quantitative damage evaluation of concrete has been proposed in RILEM TC −212ACD, by applying AE and damage mechanics in the compression test. In this study, characteristics evaluation of cracking damage effects in concrete mechanical properties by detected AE energy in core test. Prior to the compression test, distribution of micro-cracks in a concrete-core sample is inspected by helical X-ray computer tomography (CT). Then, freeze-thawed damaged samples are tested by the compression test with AE monitoring. Concrete-core samples were taken out of a channel structures in Hokkaido, Japan which is extremely developed cracking damage. Thus, it is demonstrated that the concentration of material damage could be evaluated by comparing geometrical characteristics of cracks with the "energy rate" of AE generation, which is analyzed by AE parameter analysis. A relation between AE energy rate, physical properties and geometrical properties of void is correlated, and thus the damage of concrete is qualitatively estimated by AE parameters. [ABSTRACT FROM AUTHOR]