Wood-inspired anisotropic hydrogel electrolyte with large modulus and low tortuosity realizing durable dendrite-free zinc-ion batteries.

While aqueous zinc-ion batteries exhibit great potential, their performance is impeded by zinc dendrites. Existing literature has proposed the use of hydrogel electrolytes to ameliorate this issue. Nevertheless, the mechanical attributes of hydrogel electrolytes, particularly their modulus, are suboptimal, primarily ascribed to the substantial water content. This drawback would severely restrict the dendrite-inhibiting efficacy, especially under large mass loadings of active materials. Inspired by the structural characteristics of wood, this study endeavors to fabricate the anisotropic carboxymethyl cellulose hydrogel electrolyte through directional freezing, salting-out effect, and compression reinforcement, aiming to maximize the modulus along the direction perpendicular to the electrode surface. The heightened modulus concurrently serves to suppress the vertical deposition of the intermediate product at the cathode. Meanwhile, the oriented channels with low tortuosity enabled by the anisotropic structure are beneficial to the ionic transport between the anode and cathode. Comparative analysis with an isotropic hydrogel sample reveals a marked enhancement in both modulus and ionic conductivity in the anisotropic hydrogel. This enhancement contributes to significantly improved zinc stripping/plating reversibility and mitigated electrochemical polarization. Additionally, a durable quasi-solid-state Zn//MnO2 battery with noteworthy volumetric energy density is realized. This study offers unique perspectives for designing hydrogel electrolytes and augmenting battery performance.

Stretchable Self-Healing Plastic Polyurethane with Super-High Modulus by Local Phase-Lock Strategy.

In this work, a multiblock polyurethane (PU-Im) consisting of polyether and polyurethane segments with imidazole dangling groups is demonstrated, which can further coordinate with Ni2+ . By controlling the ligand content and metal-ligand stoichiometry ratio, PU-Im-Ni complex with vastly different mechanical behavior can be obtained. The elastomer PU-2Im-Ni has extraordinary mechanical strength (61MPa) and excellent toughness (420 MJ m-3 ), but the plastic PU-4Im-Ni exhibits super-high modulus (515 MPa), strength (63 MPa), and good stretchability (≈800%). The metal-ligand interaction between polyurethane segments and Ni2+ is proved by Raman spectra, dynamic mechanical analysis (DMA), and transmission electron microscopy (TEM). The polyurethane segments domain formed by microphase separation is dynamically "locked" by Ni2+ coordinated with imidazole, revealing a local phase-lock effect. The phase-locking hard domains reinforce the PU-Im-Ni complex and maintain stimuli-responsive self-healing ability, while the free polyether segments provide stretchability. Primarily, the water environment with plasticization effect serves as an effective and eco-friendly self-healing approach for PU-Im-Ni plastic. With the excellent mechanical performance, thermal/aquatic self-healing ability, and unique damping properties, the PU-Im-Ni complexes show potential applications in self-healing engineering plastic and cushion protection fields.

Effect of Fiber-Matrix Interface Friction on Compressive Strength of High-Modulus Carbon Composites.

Carbon-fiber-reinforced polymers (CFRPs) enable lightweight, strong, and durable structures for many engineering applications including aerospace, automotive, biomedical, and others. High-modulus (HM) CFRPs enable the most significant improvement in mechanical stiffness at a lower weight, allowing for extremely lightweight aircraft structures. However, low fiber-direction compressive strength has been a major weakness of HM CFRPs, prohibiting their implementation in the primary structures. Microstructural tailoring may provide an innovative means for breaking through the fiber-direction compressive strength barrier. This has been implemented by hybridizing intermediate-modulus (IM) and HM carbon fibers in HM CFRP toughened with nanosilica particles. The new material solution almost doubles the compressive strength of the HM CFRPs, achieving that of the advanced IM CFRPs currently used in airframes and rotor components, but with a much higher axial modulus. The major focus of this work has been understanding the fiber-matrix interface properties governing the fiber-direction compressive strength improvement of the hybrid HM CFRPs. In particular, differences in the surface topology may cause much higher interface friction for IM carbon fibers compared to the HM fibers, which is responsible for the interface strength improvement. In situ Scanning Electron Microscopy (SEM)-based experiments were developed to measure interface friction. Such experiments reveal an approximately 48% higher maximum shear traction due to interface friction for IM carbon fibers compared to the HM fibers.

Crystalline Unipolymer Monolayer with High Modulus and Conductivity.

The synthesis of crystalline polymer with a well-defined orientated state and a two-dimensional crystalline size beyond a micrometer will be essential to achieve the highest physical feature of polymer material but remain challenging. Herein, we show the synthesis of the crystalline unipolymer monolayer with an unusual ultrahigh modulus that is higher than the ITO substrate and high conductance by simultaneous electrosynthesis and manipulation. We find that the polymer monolayer has fully extended in the vertical and unidirectional orientation, which is proposed to approach their theoretically highest density, modulus, and conductivity among all aggregation formations of the current polymer. The modulus and current density can reach 40 and 1000 times higher than their amorphous counterpart. It is also found that these monolayers exhibit the bias- and length-dependent multiple charge states and asymmetrically negative differential resistance (NDR) effect, indicating that this unique molecular tailoring and ordering design is promising for multilevel resistive memory devices. Our work demonstrates the creation of a crystalline polymer monolayer for approaching the physical limit of polymer electronic materials and also provides an opportunity to challenge the synthetically iterative limit of an isolated ultra-long polymer.

Polyimide Fibers with High Strength and High Modulus: Preparation, Structures, Properties, and Applications.

High strength and high modulus polyimide (HSHMPI) fibers are a type of novel high-performance organic fiber with an initial modulus higher than 90 GPa and extremely high tensile strength over 2.5 GPa realizing broad applications in the fields of electronic, engineering, aerospace, and atomic energy industries. There are currently two synthetic pathways, i.e., one-step and two-step methods, developed for the manufacture of HSHMPI fibers. An integrated fabrication process involving wet-spinning followed by thermal imidization is accepted as a typical two-step synthetic route for industrialization of HSHMPI fibers. In this article, the classification, synthetic method and technology, molecular structure, morphology, microstructures, and properties of HSHMPI fibers are summarized extensively. The effects of molecular structure and synthetic technology on the microstructures and overall performance of HSHMPI fibers are discussed. In addition, the trend in development and the application prospect of HSHMPI fibers are analyzed accordingly.

Study on the composition and properties of EME-SBS-Nano ZnO high modulus asphalt material.

The objective of this research is to address the rut problems in asphalt pavements and to resist the permanent plastic deformation with the increasing heavy traffic loads. In this paper, a new type materials of high modulus asphalt was developed by incorporating styrene-butadiene-styrene (SBS) and zinc oxide nanoparticles (nano ZnO) with an (EME)-type high modulus modifier, guided by the synergistic effects and the preparation methods of High-speed shear. The basic road performance, mechanical response and thermal stability of the new high modulus asphalt materials were analysed through basic physical indicator tests, dynamic shear rheometer tests, thermogravimetric analysis (TGA), the time-temperature superposition principle, the Refutas model, and the Christensen-Andersen-Marasteanu model. The optimal results demonstrate that the optimal blend ratio of the developed asphalt is 12% EME/8% SBS/1.5% ZnO. Under this composition, the road performance indicator values of softening point, penetration and ductility of the modified asphalt met the standard requirements. The dynamic shear rheometer tests demonstrates that the inclusion of SBS and nano ZnO considerably enhanced the shear resistance and recovery deformation capacity of EME, effectively improving the high-temperature deformation resistance of asphalt. Furthermore,the Refutas and the Christensen-Andersen-Marasteanu model fitting results showed that adding SBS and nano ZnO considerably improved the temperature sensitivity of the EME types high modulus modified asphalt and exhibiting low frequency sensitivity. Compared to PR Module-type high modulus modifier(PRM),TGA reveals that the maximum thermal weight loss of EME-SBS-ZnO decreased by 3.5441%, indicating better thermal stability and the major character of SBS,EME and asphalt is physical reaction. Moreover, EME-nano ZnO-SBS high modulus asphalt at 64 °C shows Jnr-diff = 9.5% and passes the "E" extreme traffic grade. Additionally, its cost is 4.67% lower than that of the PRM high modulus modified asphalt, presenting considerable economic benefits.

Improving Interfacial and Compressive Properties of Polyimide Fiber by Constructing Inorganic Layers on Fiber Surface.

The compressive performance of organic fiber has always been a key problem, limiting its development. In this paper, silicon oxide, alumina, and titanium oxide particles were separately deposited on the surface of high-strength and high-modulus polyimide (PI) fibers to form a structural supporting shell by using a magnetron sputtering method. The theoretical thickness was calculated by thermogravimetric analysis in good agreement with the actual thickness determined from scanning electron microscopy. The mechanics, surface, and interface properties of the measured fibers were analyzed mainly from the aspects of surface energy, interfacial shear strength (IFSS), and compression strength. The results showed that after magnetron sputtering, the inorganic shells were uniformly deposited on the surface of PI fiber, resulting in an increase in the content of inorganic elements as well as the roughness. As a result, the surface energy and IFSS of silica-coated fiber was increased by 174 and 85.6%, respectively, and compression strength was increased by 45.7%. This study provides a new approach for improving the interface property and compression strength of high-strength and high-modulus PI-fiber-reinforced composites.

A gel microparticle-based self-thickening strategy for 3D printing high-modulus hydrogels skeleton cushioned with PNAGA hydrogel mimicking anisotropic mechanics of meniscus.

Developing a meniscus substitute mimicking the anisotropic mechanics (higher circumferential tensile modulus and lower compressive modulus) of native tissue remains a great challenge. In this work, based on the pendant group structure-dependent H-bonding strengthening mechanism, two kinds of amide-based H-bonding crosslinked hydrogels with distinct mechanical behaviors, that is, the flexible poly(N-acryloyl glycinamide) (PNAGA) and the ultra-stiff poly(N-acryloylsemicarbazide) (PNASC) hydrogels are employed to construct the biomimetic meniscus substitute. To this end, a gel microparticle-based self-thickening strategy is first proposed to fabricate PNASC (GMP-PNASC) high-modulus hydrogels skeleton by extrusion printing technology in mimicking the collagen fibers in native meniscus to resist the circumferential tensile stress. Then, the PNAGA hydrogel is infused into the PNASC skeleton to replicate the proteoglycan, providing a lower compressive modulus. By regulating the structural features at the interior and peripheral regions, the GMP-PNASC/PNAGA hydrogel meniscus scaffold with the higher tensile modulus (87.28 ± 6.06 MPa) and lower compressive modulus (2.11 ± 0.28 MPa) can be constructed. In vivo outcome at 12 weeks post-implantation of rabbit's medial meniscectomy model confirms the effects of GMP-PNASC/PNAGA meniscus scaffold on alleviating the wear of articular cartilage and ameliorating the development of osteoarthritis (OA).

Development and Analysis of High-Modulus Asphalt Concrete Predictive Model.

The main purpose of this paper is to present the development of a new predictive model intended for the calculation of stiffness modulus |E*| determined by a four-point bending beam test (4PBB or 4PB-PR). The model developed, called model A, was based on the Witczak model, which was developed for the dynamic-modulus (DM) method. Most of the asphalt mixtures used to develop the model were high-modulus asphalt concrete (HMAC). The most commonly used methods for determining the stiffness modulus |E*| of asphalt mixtures were also discussed. The paper presents the results of the study for 10 asphalt mixtures but 8 of them were used to develop the predictive model. In addition, the results of complex shear modulus G* tests on neat and modified bituminous binders carried out in a dynamic shear rheometer (DSR), necessary for the development of a predictive model, are presented. The tests carried out in the dynamic shear rheometer had significant measurement uncertainties. The results of the volumetric parameters of the asphalt mixtures are also reported. The developed model A has maximum absolute errors e = 1930 MPa (p = 95%) and maximum relative errors re = 50% (p = 95%). The distribution of the absolute errors of the model, after discarding outliers, has a normal distribution as in the development of other models of this type, which was confirmed by appropriate statistical tests. On the basis of the tests and calculations carried out, it was concluded that, in order to increase the precision of the predictive models, it is advisable to reduce the measurement uncertainty of the bitumen complex shear modulus G*. For the developed model A, the limiting values of the stiffness modulus |E*| are also shown, within which the determined stiffness modulus should fall.

Synthesis and Properties of Optically Transparent Fluoro-Containing Polyimide Films with Reduced Linear Coefficients of Thermal Expansion from Organo-Soluble Resins Derived from Aromatic Diamine with Benzanilide Units.

Wholly aromatic polyimide (PI) films with good solution processability, light colors, good optical transparency, high storage modulus, and improved heat resistance were prepared and characterized. For this purpose, a multi-component copolymerization methodology was performed from a fluoro-containing dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), a rigid dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and a fluoro-containing diamine, 2,2'-bis(trifluoromethyl)-4,4'-bis [4-(4-amino-3-methyl)benzamide]biphenyl (MABTFMB). One homopolymer, FPI-1 (6FDA-MABTFMB), and five copolymers, FPI-2~FPI-6, containing the BPDA units from 10 mol% to 50 mol% in the dianhydride moieties, were prepared, respectively. The derived PI resins showed good solubility in the polar aprotic solvents, such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc). The flexible PI films obtained by the solution casting procedure showed good optical properties with the transmittances higher than 74.0% at the wavelength of 450 nm. The PI films exhibited excellent thermal properties, including 5% weight loss temperatures (T5%) over 510 °C, together with glass transition temperatures (Tg) over 350.0 °C according to the peak temperatures of the loss modulus in dynamical mechanical analysis (DMA) measurements. The FPI-6 film also showed the lowest linear coefficient of thermal expansion (CTE) value of 23.4 × 10-6/K from 50 to 250 °C according to the thermomechanical analysis (TMA) measurements, which was obviously lower than that of FPI-1 (CTE = 30.6 × 10-6/K).

Revealing the High-Modulus Mechanism of Polyimide Films Prepared with 3,4'-ODA.

To prepare PIs (polyimides) with desirable thermal and mechanical properties is highly demanded due to their widespread applications in flexible optoelectronic devices and printed circuit boards. Here, the PI films of BPDA/4,4'-ODA, BPDA/3,4'-ODA, PMDA/4,4'-ODA, PMDA/3,4'-ODA systems were prepared, and it was found that the PIs with 3,4'-ODA always exhibit a high modulus compared with the PIs with 4,4'-ODA. To disclose the mechanism of high-modulus PI films with 3,4'-ODA, amorphous PI models and uniaxial drawing PI models were established and calculated based on MD simulation. The PI structural deformations at different length scales, i.e., molecular chain cluster scale and repeat unit scale, under the same stress were detailed and analyzed, including the variation of chain conformation, bond length, bond angle, internal rotation energy, and torsion angle. The results indicate that PIs with 3,4-ODA have higher internal rotation energy and smaller deformation with the same stress, consistent with the high modulus.

Research on Improving the Durability of Bridge Pavement Using a High-Modulus Asphalt Mixture.

In order to improve the durability of the asphalt pavement on a cement concrete bridge, this study investigated the effect of the modulus of the asphalt mixture at the bottom layer on the mechanical response of bridge pavement, along with a type of emerging bridge pavement structure. In addition, the design method and pavement performance of a high-modulus asphalt mixture were investigated using laboratory and field tests, and the life expectancy of the deck pavement structure was predicted based on the rutting deformation. The results showed that the application of a high-modulus asphalt mixture as the bottom asphalt layer decreased the stress level of the pavement structure. The new high-modulus asphalt mixture displayed excellent comprehensive performance, i.e., the dynamic stability reached 9632 times/mm and the fatigue life reached 1.65 million cycles. Based on the rutting depth prediction, using high-modulus mixtures for the bridge pavement prolonged the service life from the original 5 years to 10 years, which significantly enhanced the durability of the pavement structure. These research results could be of potential interest for practical applications in the construction industry.

A high value utilization process for coal gasification slag: Preparation of high modulus sodium silicate by mechano-chemical synergistic activation.

Coal gasification coarse slag (CGCS) is solid waste generated during coal gasification. The mainly treatment method of CGCS is storage and landfill, which causes severe environmental pollution and waste of land resources. Sodium silicate can be synthesized using CGCS after impurities are removed for the high content of amorphous silica. In this work, a novel method of acid activation depolymerization-dilute alkali dissociation is proposed to synthesize high-modulus, low-impurity sodium silicate using CGCS under mild conditions. In the acid activation depolymerization process, the content of impurities such as CaO and Fe2O3 can be reduced from over 30% to below 3%. SiO2 composition can be enriched from 35.75% to 60.60%. The SiOAl bond is broken, the coordination structures of Q4(2Al) and Q4(3Al) are depolymerized, and the reactive Q4(0Al) and Q3(0Al) coordination structures of amorphous silica are formed. Numerous defects appear in the aluminosilicate structure, exposing a large number of active SiOH bonds. Efficient desilicated ratio is increased from 7.59% to 73.45%. During the process of dilute alkali dissociation, a large number of reactive SiOSi bonds with network structure defects are broken with the destruction of hydroxyl groups, while SiO and SiOH bonds are formed. Amorphous silica is leached into the liquid phase in the form of oligomers, and high-modulus sodium silicate can be obtained. Under optimal conditions, the removal ratio of amorphous silica and modulus of sodium silicate can reach 80% and 3.53, respectively. The synthesized sodium silicate can be used to produce hydrated silica, adhesives and surface coatings. This process not only reduces pollution, but also alleviates the shortage of high-purity quartz sand resources and promotes the clean development of coal chemical enterprises.

Evaluating the Rheological Properties of High-Modulus Asphalt Binders Modified with Rubber Polymer Composite Modifier.

With the increasing traffic loading and changing climatic conditions, there is a need to use novel superior performing pavement materials such as high-modulus asphalt binders and asphalt mixtures to mitigate field distress such as rutting, cracking, etc. This laboratory study was thus conducted to explore and substantiate the usage of Rubber Polymer Composite Modifier (RPCM) for high-modulus asphalt binder modification. The base asphalt binder used in the study comprised A-70# Petroleum asphalt binder with RPCM dosages of 0.25%, 0.30%, 0.35%, 0.40% and 0.45%, separately. The laboratory tests conducted for characterizing the asphalt binder rheological and morphological properties included the dynamic mechanical analysis (DM), temperature-frequency sweep in the dynamic shear rheometer (DSR) device, bending beam rheometer (BBR), and florescence microscopic (FM) imaging. The corresponding test results exhibited satisfactory compatibility and potential for using RPCM as a high-modulus asphalt binder modifier to enhance the base asphalt binder's rheological properties, both with respect to high- and low-temperature performance improvements. For the A-70# Petroleum asphalt binder that was evaluated, the optimum RPCM dosage was found to be 0.30-0.35%. In comparison to styrene-butadiene-styrene (SBS), asphalt binder modification with RPCM exhibited superior high-temperature rutting resistance properties (as measured in terms of the complex modulus and phase angle) and vice versa for the low-temperature cracking properties. Overall, the study beneficially contributes to the literature through provision of a reference datum toward the exploratory usage of RPCM for high-modulus asphalt binder modification and performance enhancements.

Novel fabrication of high-modulus cellulose-based films by nanofibrillation under alkaline conditions.

We herein propose a novel continuous process for fabricating high-modulus films based on cellulose nanofibers. In place of a dissolution process, the pulps were mechanically disintegrated into nanofibers by ball-milling in an 8% NaOH solution. NaOH treatment loosened the hydrogen bonding between the cellulose microfibrils in the pulps, and a highly concentrated suspension (8%) of cellulose nanofibers with a uniform diameter of approximately 20-50 nm was prepared after ball-milling for 90 min. The resulting nanofiber suspensions prepared in the NaOH solution exhibited the crystal forms of both Cellulose I and Cellulose II, although the Cellulose II content gradually increased upon increasing the milling time. Finally, hydrogels were formed following neutralization of the suspensions, and the hydrogel sheets were hot-pressed into thin films at 120 °C. The Young's moduli of the films were significantly higher than those of typical regenerated cellulose films due to the presence of some remaining Cellulose I and a high crystallinity.

Nonflammable and High-Voltage-Tolerated Polymer Electrolyte Achieving High Stability and Safety in 4.9 V-Class Lithium Metal Battery.

High-voltage polymer electrolytes play important roles in achieving high-energy-density polymer electrolyte-based batteries, but the pace of progress moves slowly, since oxidation-resistant polymer electrolytes at high voltages are rarely obtained. Herein, we reported a nonflammable and high-voltage-tolerated polymer electrolyte (HVTPE) with extended voltage of 5.5 V. The obtained HVTPE has lower HOMO energy indicating a higher antioxidation ability, which avoids the decomposition and depletion of electrolyte near the cathode. Significantly, the HVTPE-based 4.45 V-class LiCoO2 battery delivered a high capacity of 173.2 mA h g-1 at 0.05 C. Using 4.9 V-class LiNi0.5Mn1.5O4 as a cathode, the battery exhibited stable cycling performance. Moreover, HVTPE showed a high modulus of 2.3 GPa, which can efficiently restrain the penetration of Li dendrites, and desirable nonflammable feature, leading to the enhanced safety based on polymer electrolytes. The current work opens new avenues to realize high-voltage polymer electrolyte-based batteries with high safety.

Chirality-Enabled Liquid Crystalline Physical Gels with High Modulus but Low Driving Voltage.

Self-supporting liquid crystalline physical gels with facile electro-optic response are highly desirable, but their development is challenging because both the storage modulus and driving voltage increase simultaneously with gelator loading. Herein, we report liquid crystalline physical gels with high modulus but low driving voltage. This behavior is enabled by chirality transfer from the molecular level to three-dimensional fibrous networks during the self-assembly of 1,4-benzenedicarboxamide phenylalanine derivatives. Interestingly, the critical gel concentration is as low as 0.1 wt %. Our findings open doors to understanding and exploiting the role of chirality in organic gels.

Corneal, Conjunctival effects and blood flow changes related to silicone hydrogel lens wear and their correlations with end of day comfort.

PURPOSE: First, to examine how wearing high and low modulus lenses with two different base curves affected lens fit, and the corneal tissue and bulbar conjunctival vascular tissue (bulbar redness and blood velocity). Secondly, to quantify the associations between these baseline and outcome variables and the third purpose was to correlate these variables with end of day comfort. METHODS: Thirty participants wore higher (PureVision (PV) 8.3, 8.6) and lower (Acuvue Advance (AA) 8.3, 8.7) modulus silicone hydrogel lenses for two weeks on a daily wear basis. Lens fitting characteristics were examined. Corneal epithelial thickness was measured and the cornea and conjunctiva were assessed. RBC velocity was estimated from high magnification bulbar conjunctival images. Subjective comfort/dryness was reported by participants using visual analogue scales. RESULTS: AA lenses were rated the most comfortable (ANOVA, p=0.041). The least movement was while using the AA 8.3 base curve lens (Tukey p=0.028). Steep AA and PV lenses showed significantly higher conjunctival staining at the 2 week visit (ANOVA, p=0.029). There was a significant decrease in RBC velocity with both steeper AA lenses vs PV lenses (Tukey, p=0.001). Comparing baseline and 2 week visits, there was a significant negative correlation for the PV 8.3 between comfort and superior bulbar staining (r=-0.53). For both the PV 8.3 and AA 8.3 reduced RBC velocity was correlated with dryness (r=0.61 and r=0.91, respectively). CONCLUSIONS: Physical differences in contact lenses affect structural and vascular functional aspects of the ocular surface and these may be associated with symptoms of dryness.

Viscoelastic Mechanical Responses of HMAP under Moving Load.

In order to represent the mechanical response laws of high-modulus asphalt pavement (HMAP) faithfully and objectively, the viscoelasticity of high-modulus asphalt mixture (HMAM) was considered, and the viscoelastic mechanical responses were calculated systematically based on moving load by numerical simulations. The performances of the HMAP in resistance to the deformation and the cracking at the bottom layer were compared with the ordinary asphalt pavement. Firstly, Lubao and Honeywell 7686 (H7686) were selected as the high modulus modifiers. The laboratory investigations of Asphalt mix-70 penetration, Asphalt mix-SBS (styrene-butadiene-styrene), HMAM-Lubao and HMAM-H7686 were carried out by dynamic modulus tests and wheel tracking tests. The conventional performances related to the purpose of using the HMAM were indicated. The master curves of the storage moduli were obtained and the viscoelastic parameters were fitted based on viscoelastic theories. Secondly, 3D pavement models based on moving loads for the viscoelastic structures were built using the non-linear finite element software ABAQUS. The wheel path was discretized in time and space to apply the Haversine wave load, and then the mechanical responses of four kinds of asphalt pavement were calculated. Finally, the sensitivity analysis was carried out. The results showed that the addition of the high modulus modifiers can improve the resistance to high-temperature rutting of the pavements. Except for the tensile strain and stress at the bottom of the underlayer, other responses decreased with the increases of the dynamic moduli and the change laws of the tensile strain and stress were affected by the range of the dynamic modulus. The tensile stress at the bottom of the asphalt layer would be too large if the modulus of the layer were too large, and a larger tensile strain would result. Therefore, the range of the modulus must be restricted to avoid the cracking due to excessive tension when using the HMAM. The resistance of the HMAP to deformation was better and the HMAP was less sensitive to load changes and could better withstand the adverse effects inflicted by heavy loads.

Effect of hydroxyapatite concentration on high-modulus composite for biodegradable bone-fixation devices.

There are over 3 million bone fractures in the United States annually; over 30% of which require internal mechanical fixation devices to aid in the healing process. The current standard material used is a metal plate that is implanted onto the bone. However, metal fixation devices have many disadvantages, namely stress shielding and metal ion leaching. This study aims to fix these problems of metal implants by making a completely biodegradable material that will have a high modulus and exhibit great toughness. To accomplish this, long-fiber poly-l-lactic acid (PLLA) was utilized in combination with a matrix composed of polycaprolactone (PCL) and hydroxyapatite (HA) nano-rods. Through single fibril tensile tests, it was found that the PLLA fibers have a Young's modulus of 8.09 GPa. Synthesized HA nanorods have dimensions in the nanometer range with an aspect ratio over 6. By dip coating PLLA fibers in a suspension of PCL and HA and hot pressing the resulting coated fibers, dense fiber-reinforced samples were made having a flexural modulus up to 9.2 GPa and a flexural strength up to 187 MPa. The flexural modulus of cortical bone ranges from 7 to 25 GPa, so the modulus of the composite material falls into the range of bone. The typical flextural strength of bone is 130 MPa, and the samples here greatly exceed that with a strength of 187 MPa. After mechanical testing to failure the samples retained their shape, showing toughness with no catastrophic failure, indicating the possibility for use as a fixation material. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1963-1971, 2017.