Fiber Elastic Modulus Research Articles

Preliminary Experimental and Numerical Study of the Tensile Behavior of a Composite Based on Sycamore Bark Fibers

In the context of global sustainable development, using natural fibers as reinforcement for composites have become increasingly attractive due to their lightweight, abundant availability, renewability, and comparable specific properties to conventional fibers. This paper investigates the tensile properties of a sycamore bark fiber-reinforced composite. The tensile tests using digital image correlation showed that, by adding 18% by volume of sycamore bark for the polyester matrix, the tensile modulus achieves 4788.4 ± 940.1 MPa. Moreover, the tensile strength of the polyester resin increased by approximately 90% when reinforced with sycamore bark fiber, achieving a tensile strength of 64.5 ± 13.4 MPa. These mechanical properties are determined by the way loads are transferred between the polyester matrix and fibers and by the strength of the bond between the fiber-matrix interfaces. Since it is difficult and time consuming to characterize the mechanical properties of natural fibers, an alternative approach was proposed in this study. The method consists of the identification of the fiber elastic modulus using a finite element analysis approach, based on tensile tests conducted on the sycamore bark fiber-reinforced composites. The model correctly describes the overall composite behavior, a good agreement is found between the experimental, and the finite element predicted stress–strain curves. The identified sycamore bark fiber elastic modulus is 17,763 ± 6051 MPa. These results show that sycamore bark fibers can be used as reinforcements to produce composite materials.

Shear wave propagation in a fiber-laden viscoelastic waveguide under prestress: Inverse modeling challenges

The functional role of skeletal muscle and the hierarchal microstructure and arrangement of fibers within it results in anisotropy and inhomogeneity in both material properties and imposed stresses. Dynamic elastography reconstruction methods for estimating muscle tissue viscoelastic properties that are based on assumptions of homogeneity, isotropy and only bulk wave motion may produce inaccurate estimates. Biases may be introduced in reconstruction by homogenizing muscle with axially aligned fibers and approximating it as transversely isotropic. The significance of these biases, and their interplay with imposed stresses and confounding waveguide effects due to small cross-sectional dimensions, is quantified with a series of numerical finite element and experimental elastography studies on cylindrically-shaped fiber-laden muscle phantoms, with varying fiber dimensions. Specifically, numerical simulations of elastography are conducted on 4-, 60- and 113-fiber models with the aligned fiber cross-sectional area fixed (reduced fiber diameter as fiber count increases) and comprising approximately 40% of the cross-sectional area of the cylindrical phantom that is also undergoing tensile axial pre-loading. Fiber elastic moduli twice that of connective tissue are considered. Experimental studies of the 4-fiber model are used to validate the numerical model. [Funding support: NSF 1852691 and NIH AR071162]

Numerical Investigation of Stress-Strain State Effects on Strain Measurements with Fiber Bragg Grating Sensors

This study investigates the behaviour of resonant wavelengths of Fiber Bragg Gratings (FBG) inscribed within optically isotropic fibers under transverse loading, both in free and embedded conditions. A numerical-analytical approach is employed, utilizing the finite element method to calculate strain tensor components in the optical fiber core, followed by an analytical determination of resonant wavelengths and reflected FBG spectrum shape. The research demonstrates the influence of the ratio of host material and optical fiber elastic moduli on the birefringence level in FBG area under transversal loading. Based on analytical model of FBG spectrum simulation the discrepancy between analytically calculated and experimentally recorded resonant wavelength shifts in FBG embedded within isotropic material under varying transverse load levels is demonstrated.

Bio-inspired based meta-heuristic approach for predicting the strength of fiber-reinforced based strain hardening cementitious composites

A recently introduced bendable concrete having hundred times greater strain capacity provides promising results in repair of engineering structures, known as strain hardening cementitious composites (SHHCs). The current research creates new empirical prediction models to assess the mechanical properties of strain-hardening cementitious composites (SHCCs) i.e., compressive strength (CS), first crack tensile stress (TS), and first crack flexural stress (FS), using gene expression programming (GEP). Wide-ranging records were considered with twelve variables i.e., cement percentage by weight (C%), fine aggregate percentage by weight (Fagg%), fly-ash percentage by weight (FA%), Water-to-binder ratio (W/B), super-plasticizer percentage by weight (SP%), fiber amount percentage by weight (Fib%), length to diameter ratio (L/D), fiber tensile strength (FTS), fiber elastic modulus (FEM), environment temperature (ET), and curing time (CT). The performance of the models was deduced using correlation coefficient (R) and slope of regression line. The established models were also assessed using relative root mean square error (RRMSE), Mean absolute error (MAE), Root squared error (RSE), root mean square error (RMSE), objective function (OBF), performance index (PI) and Nash-Sutcliffe efficiency (NSE). The resulting mathematical GP-based equations are easy to understand and are consistent disclosing the originality of GEP model with R in the testing phase equals to 0.8623, 0.9269, and 0.8645 for CS, TS and FS respectively. The PI and OBF are both less than 0.2 and are in line with the literature, showing that the models are free from overfitting. Consequently, all proposed models have high generalization with less error measures. The sensitivity analysis showed that C%, Fagg%, and ET are the most significant variables for all three models developed with sensitiveness index higher than 10 %. The result of the research can assist researchers, practitioners, and designers to assess SHCC and will lead to sustainable, faster, and safer construction from environment-friendly waste management point of view.

The effect of fatty infiltration, revision surgery, and sex on lumbar multifidus passive mechanical properties.

Previous research has demonstrated increased stiffness in the multifidus muscle compared to other paraspinal muscles at the fiber bundle level. We aimed to compare single fiber and fiber bundle passive mechanical properties of multifidus muscle: (1) in 40 patients undergoing primary versus revision surgery and (2) in muscle with mild versus severe fatty infiltration. The degree of muscle fatty infiltration was graded using the patients' spine magnetic resonance images. Average single fiber and fiber bundle passive mechanical properties across three tests were compared between primary (N = 30) and revision (N = 10) surgery status, between mild and severe fatty infiltration levels, between sexes, and with age from passive stress-strain tests of excised multifidus muscle intraoperative biopsies. At the single fiber level, elastic modulus was unaffected by degree of fatty infiltration or surgery status. Female sex (p = 0.001) and younger age (p = 0.04) were associated with lower multifidus fiber elastic modulus. At the fiber bundle level, which includes connective tissue around fibers, severe fatty infiltration (p = 0.01) and younger age (p = 0.06) were associated with lower elastic modulus. Primary surgery also demonstrated a moderate, but non-significant effect for lower elastic modulus (p = 0.10). Our results demonstrate that female sex is the primary driver for reduced single fiber elastic modulus of the multifidus, while severity of fatty infiltration is the primary driver for reduced elastic modulus at the level of the fiber bundle in individuals with lumbar spine pathology.

Effect of extracellular matrix fiber cross-linkage on cancer cell motility and surrounding matrix deformation

Cancer incidence is increasing annually, and the invasion of cancer into the stroma significantly affects cancer metastasis. The stroma primarily comprises an abundant extracellular matrix (ECM) that interacts closely with cancer cells. Cancer cells use the ECM as a scaffold to migrate from a tumor via mechanical actions such as pushing and pulling the fibers. The purpose of this study is to clarify the effects of elastic modulus differences on cell migration behavior based on the same ECM fiber structure. We observe temporal changes in the morphology of cancer cells and the surrounding ECM to elucidate the relationship between changes in the mechanical properties of the ECM and the invasive behavior of cancer cells. We analyze the shape and migration distance of cancer cells and the displacement field of the ECM by varying the fiber elastic modulus but fixing the ECM density. Increasing the elastic modulus results in a protruding cell shape, which indicates the maximum displacement of the ECM around the cell. Additionally, differences in cell migration speed and dispersion based on the elastic modulus are observed. The behavior of cells with increasing elasticity is classified via cluster analysis. Owing to the chemical cross-linking of the fibers, some cells cannot deform the surrounding tissue. This is attributable to the gel state of the ECM and microscopic fluctuations in the fiber density around the cells. We successfully assessed the effect of changes in the ECM modulus on cell mortality and morphology to reveal the mechanism of cancer invasion.

A direct fiber approach to model sclera collagen architecture and biomechanics

Sclera collagen fiber microstructure and mechanical behavior are central to eye physiology and pathology. They are also complex, and are therefore often studied using modeling. Most models of sclera, however, have been built within a conventional continuum framework. In this framework, collagen fibers are incorporated as statistical distributions of fiber characteristics such as the orientation of a family of fibers. The conventional continuum approach, while proven successful for describing the macroscale behavior of the sclera, does not account for the sclera fibers are long, interwoven and interact with one another. Hence, by not considering these potentially crucial characteristics, the conventional approach has only a limited ability to capture and describe sclera structure and mechanics at smaller, fiber-level, scales. Recent advances in the tools for characterizing sclera microarchitecture and mechanics bring to the forefront the need to develop more advanced modeling techniques that can incorporate and take advantage of the newly available highly detailed information. Our goal was to create a new computational modeling approach that can represent the sclera fibrous microstructure more accurately than with the conventional continuum approach, while still capturing its macroscale behavior. In this manuscript we introduce the new modeling approach, that we call direct fiber modeling, in which the collagen architecture is built explicitly by long, continuous, interwoven fibers. The fibers are embedded in a continuum matrix representing the non-fibrous tissue components. We demonstrate the approach by doing direct fiber modeling of a rectangular patch of posterior sclera. The model integrated fiber orientations obtained by polarized light microscopy from coronal and sagittal cryosections of pig and sheep. The fibers were modeled using a Mooney-Rivlin model, and the matrix using a Neo-Hookean model. The fiber parameters were determined by inversely matching experimental equi-biaxial tensile data from the literature. After reconstruction, the direct fiber model orientations agreed well with the microscopy data both in the coronal plane (adjusted R2 = 0.8234) and in the sagittal plane (adjusted R2 = 0.8495) of the sclera. With the estimated fiber properties (C10 = 5746.9 MPa; C01 = −5002.6 MPa, matrix shear modulus 200 kPa), the model's stress-strain curves simultaneously fit the experimental data in radial and circumferential directions (adjusted R2's 0.9971 and 0.9508, respectively). The estimated fiber elastic modulus at 2.16% strain was 5.45 GPa, in reasonable agreement with the literature. During stretch, the model exhibited stresses and strains at sub-fiber level, with interactions among individual fibers which are not accounted for by the conventional continuum methods. Our results demonstrate that direct fiber models can simultaneously describe the macroscale mechanics and microarchitecture of the sclera, and therefore that the approach can provide unique insight into tissue behavior questions inaccessible with continuum approaches.

Efficient training of two ANNs using four meta-heuristic algorithms for predicting the FRP strength

In recent years, artificial neural network (ANN) is one of the popular and effective machine learning models that can be used to accurately predict fiber reinforced polymer (FRP) strength. However, the ANN structure and parameters are usually are chosen by experience. In this study, the aim is to use the combination of meta-heuristic algorithm with two different types of artificial neural network structure to optimize the parameters of the feed forward backpropagation and radial basis function networks. In this paper, Particle swarm optimization (PSO), Genetic algorithm (GA), Colliding bodies optimization (CBO), Enhanced colliding bodies optimization (ECBO) algorithms are used to combine with ANNs.A total of 223 test data on Carbon FRP (CFRP) collected from the available literature were used to generate training and test data sets. Various validation criteria such as mean square error, root mean square error and correlation coefficient (R) are used to validate the models. These models consider the effects of concrete compressive strength, concrete sample diameter, concrete sample length, fiber elastic modulus, fiber thickness, fiber strength on the ultimate strength of FRP-concrete.It is shown that ECBO algorithm provide better results and higher accuracy. Also, the comparison of the results of using two neural networks, feed forward backpropagation (FFB) and radial basis function (RBF), indicates that the lower error percentage and more accurate results are related to the FFB neural networks combined with ECBO.

A comprehensive quantitative bottom-up analysis of fiber-reinforced recycled-aggregate concrete behavior

This study provides a more profound understanding of the influence of the phases of fiber-reinforced recycled-aggregate concrete (FRRAC), on its elastic properties, in particular Young’s modulus and Poisson’s ratio. Multi-scale modeling analyses of mortar and FRRAC were conducted to assess the effect of variations in the fiber content, fiber elastic modulus, RA content, and water-to-cement ratio (w/c) on the elastic properties at each scale. Thus, the analytic Mori–Tanaka (MT) homogenization algorithm developed in Python programming language and the three-dimensional finite element (FE) homogenization scheme were applied to evaluate the elastic properties of FRRAC. As such, different fiber types including steel, basalt, glass, and propylene, at a volume fraction range of 0–2%, along with the variations in fiber elastic modulus, and different RA replacement levels ranging from 0 to 100% were incorporated in the modeling process at different w/c ratio. Based on the results, the Poisson’s ratio of steel FRRAC in the MT approach surges with increasing fiber content. Furthermore, the elastic modulus of FRRAC is highly susceptible to an increase in Young’s modulus of polypropylene fiber, among other fiber types. The elastic modulus of concrete experiences a sharp decrease with increasing w/c for all fiber types in both FE and MT approaches.

Homogeneity versus inhomogeneity in muscle elastography

The hierarchal microstructure and arrangement of skeletal muscle fibers results in both anisotropy and inhomogeneity. Most elastography reconstruction methods assume homogeneity and many also assume isotropy. In this computational (finite element) and experimental (MR) elastography study we investigate the impact of assuming homogeneity as muscle architecture dimensions and property differences are varied. This analysis also takes into consideration the inherent anisotropy (transverse isotropy) created by homogenization of the fiber structure, and the added complication ofnonhomogeneous (pre-stress) boundary conditions. Specifically, the computational harmonic analysis uses a parametric sweep across 200 Hz to 2000Hz applied to 4-, 40- and 400-fiber models with the aligned fiber cross-sectional area fixed (reduced fiber diameter as fiber count increases) and comprising 50% of the circular cross-sectional area in the fixed diameter cylindrical phantom. Fiber elastic moduli two to five times that of connective tissue are considered. This phantom also undergoes tensile axial pre-loading simultaneous to elastography studies. Predicted results are compared to a homogeneous transverse isotropic model that is reached in the limit as the fiber count increases to infinity while still summing to 50% of the cross-sectional area. Selected cases, such as the 4-fiber model are also evaluated experimentally using MR elastography.

Influence of Synthetic Fibers on the Flexural Properties of Concrete: Prediction of Toughness as a Function of Volume, Slenderness Ratio and Elastic Modulus of Fibers.

The construction industry requires concrete with adequate post-cracking behavior for applications such as tunnels, bridges, and pavements. For this reason, polypropylene macrofibers are used, which are synthetic fibers that fulfill the function of providing residual strength to concrete. In this study, an experimental plan is carried out to evaluate the bending behavior of concrete reinforced with polypropylene fibers using the four-point bending test according to ASTM C1609. Three fiber dosages (3.6, 7.2 and 10.8 kg/m3) and three fiber lengths (40, 50, and 60 mm) were used. The use of macro polypropylene fibers increased the post-cracking behavior of concrete. In addition, based on the experimentally obtained results and available literature data, a multivariable equation was developed to predict the concrete toughness as a function of the volume, slenderness, and modulus of elasticity of the fibers. A Pearson's correlation coefficient, r of 0.90, showed a strong correlation between the developed equation and the experimental data. From this equation, it was possible to determine the participation of the following parameters in calculating toughness. The participation or weight of the fiber's modulus of elasticity on the concrete's tenacity is 26%, the volume of the fiber is 39%, the slenderness is 19%, and the reinforcement index is 16%.

Crashworthiness optimization of crash box with 3D-printed lattice structures

Crash boxes are important energy-absorbing components to ensure the passive safety of automobile vehicles during crashworthiness. The current study presents an investigation of a novel crash box, which consists of Al shell and 3D-printed lattice core. In view of obtaining a good lightweight and energy absorption, the lattice structures are fabricated by fused filament fabrication (FFF) technology using carbon fiber reinforced polyamide 6 (PA6/CF) composites. First, the correlations between fiber content and elastic modulus, maximum tensile stress are established by a least squares method. Four different lattice structures including hexagonal, kagome, re-entrant and triangular honeycombs are additive-manufactured. The results reveal that the experimental data from compression test is in good agreement with the simulation analysis, and the kagome achieves the maximum specific energy absorption (SEA) values through numerical analysis. Then, an integrated “material-structure” model is constructed in an Isight environment to analyze the sensitivity of the material property (elastic modulus (E), tensile strength (σ) and fracture strain (ε)) and geometric parameters (thickness (t) and unit size (r) on the crashworthiness performance. A multi-objective optimization strategy with maximum SEA and minimum mass as objectives for the novel crash box is established using response surface model approach and optimal Latin hypercube. Simulation results show that the crash box optimized by non-dominated sorting genetic algorithm (NSGA-II) algorithm can improve the energy absorption with mass reduction, which provides some reference for the structural design and optimization of the crash box.

Predicting ultimate condition and transition point on axial stress–strain curve of FRP-confined concrete using a meta-heuristic algorithm

Accurately predicting key reference points on the axial stress-strain curve of fiber-reinforced polymer (FRP)-confined concrete is of great importance for the pre-design and modeling of structures manufactured with this composite system. This paper presents a detailed study on the development of accurate and practical expressions for predicting the ultimate condition and transition point, as key reference points, on axial stress-strain curves of FRP-confined concrete using generic programming (GP). A comprehensive data tuning and cross-validation analysis was firstly performed to develop prediction models. Afterwards, the accuracy and performance of the developed empirical expressions were examined by sensitivity analysis, parametric analysis and model validation. Finally, a comparison was made between the performance of these proposed expressions and that of the existing best-performing expressions in the literature using statistical analysis. Based on the sensitivity and parametric analysis of the database, it is shown that: compressive strength ( f’ cc ) and axial transition strain ( ɛ c1 ) are more sensitive to FRP lateral stiffness ( K l ); ultimate axial strain ( ɛ cu ) is more sensitive to K l -to-unconfined compressive strength ( f’ co ) ratio and fiber ultimate tensile strain ( ɛ fu ); hoop rupture strain ( ɛ h,rup ) is more sensitive to fiber elastic modulus ( E f ); and axial transition strength ( f’ c1 ) is more sensitive to f’ co . It is also shown that the proposed expressions provided more accurate predictions of the ultimate condition and transition point on the axial stress-strain curve of FRP-confined concrete than the existing expressions. This was achieved by using a larger number of datasets and accurately capturing the effects of the most influential input parameters in the proposed expressions.

Mechanical Properties of Polyethylene Fiber Reinforced Ultra High Performance Concrete (UHPC).

Ultra-high performance concrete (UHPC) is a kind of cement-based material with ultra-high strength, high toughness and excellent durability. However, the tensile strain capacity of UHPC is often below 0.5%, and the mode of single crack failure is the main failure pattern, which limits the development of UHPC. In order to overcome the weakness of the relatively low strain capacity of UHPC, five types of polyethylene (PE) fibers with different geometrical and mechanical parameters (length, diameter and elastic modulus) were added into the matrix, and the corresponding mechanical behavior was investigated. The experimental results showed that the high fiber length and fiber diameter of PE fibers are a benefit for the compressive strength and tensile strength of UHPC. The increase of the fiber diameter and elastic modulus remarkably attributed to the increase in the tensile strain capacity of UHPC. With the increase of the fiber diameter and elastic modulus, the overall energy absorption capacity G and the energy absorption capacity of the substrate prior to the softening section ga of UHPC were both enhanced. The diameter of PE fiber was the main factor affecting the energy consumption of UHPC. Among the five types of PE fiber, PF fiber (PF fiber is PF type polyethylene fiber; Fiber length: 15 mm; Fiber diameter: 27 μm; Elastic Modulus: 117 GPa) is the optimal fiber to increase the tensile mechanical behavior of UHPC.

Effects of Fiber and Surface Treatment on Airport Pavement Concrete against Freeze-Thawing and Salt Freezing.

Airport pavement concrete often suffers from freeze-thawing damage in high latitude and cold areas. In addition, the use of aircraft deicer makes the airport pavement concrete suffer from salt-freezing damage. To improve the durability of airport pavement concrete, modified polyester synthetic fiber (FC), cellulose fiber (CF), and basalt fiber (BF) reinforced concrete were prepared in this paper. The mechanical strength, pore structure, and frost resistance (freeze-thawing and salt freezing) of fiber-reinforced concrete were investigated. The effects of the combined action of fiber (fiber type and content) and surface treatment methods (spraying silane and impregnating silane) on the frost resistance of concrete were investigated. The results show that the flexural strength of concrete is positively correlated with the elastic modulus of fiber, but has little effect on the compressive strength. Fiber can reduce mass loss and dynamic modulus loss of concrete subjected to frost damage. FC more effectively improved the frost resistance of concrete than CF. After 30 cycles of salt freezing, the spalling amount of concrete sprayed or soaked with silane was decreased by 65.5% and 55.5%, respectively. Adding fiber and impregnating silane reduced the spalled concrete by up to 70.5%. Spraying silane treatment is better than impregnating silane treatment in enhancing the frost resistance of concrete because a better silane condensation reaction is achieved with spraying silane.

Study on Shielding and Radiation Resistance of Basalt Fiber to Gamma Ray.

In this study, four basalt rocks were selected to produce continuous fibers, the chemical composition of basalt rocks and the corresponding fibers were compared using the XRF, the results reveal that the content of the chemical component present in the basalt fibers is consistent with basalt rocks. The mass attenuation coefficient of different fibers was analyzed using the XCOM program, the results indicate that when the incident electron energy is 0.01~0.1 MeV, fiber mass attenuation coefficient is found to be positively correlated with the content of Wt (Fe2O3 + MnO + TiO2 + CaO + K2O). The structure and properties of the fibers irradiated by different absorption doses of gamma rays were studied using the SEM, EDX and FTIR, the results indicate that irradiation produces no effect on the basalt fiber structure, surface morphology, and contents of the surface elements, the mass loss rate of the fiber was much less than 1%, fiber tensile strength and elastic modulus increased 4.7–7.5% and 3.9–9.1%, respectively, but the elongation at break of fiber decreased 4.18–10.97%. Two selected basalt fiber cloths of thickness 0.12 and 0.28 mm were irradiated with gamma rays of energies of 100 and 120 keV to examine the shielding property of basalt fibers against the gamma rays, when the energy was 100 keV, the shielding ratios of the fiber cloths were 18.9% and 22.5%, respectively, but when the energy was 120 keV, the shielding ratios of the fiber cloths decreased significantly and were at 8.7% and 10.4%, respectively. When the irradiated electron energy is 100 keV, the shielding ratio for basalt fiber cloths measuring 0.12 and 0.28 mm can reach up to 38.9% and 46.3% of that of the 0.5-mm lead plate, respectively.

Finite element modeling effects of fiber performance on pilling of polyester–cotton woven fabrics

This paper aims to numerically establish the effects of polyester fiber performance on the pilling of polyester–cotton woven fabrics, including pilling grades, overall energy absorption and the forms of energy absorption. Geometric models of fabric and hairiness are established using the Python programming language based on the length and density distribution of hairiness on the fabric surface. The finite element method is adopted to simulate the pilling process of polyester–cotton woven fabrics with different polyester fiber performance parameters. The simulated pilling grades of fabrics are fairly close to the practical pilling grades, whose relative error is 7.3%. With the increase of fiber diameter, pilling grades decrease. Increasing the fiber friction coefficient also affects pilling grades, which firstly decrease and then increase. Pilling grades reduce with the increased fiber elastic modulus. Friction dissipation energy during pilling becomes the dominant form of energy. When the fiber diameter is less than 14 μm, the fiber friction coefficient is between 0.3 and 0.4 and the fiber elastic modulus is greater than 4.55 GPa, fabrics start pilling.

Physicomechanical properties and in vitro release behaviors of electrospun ibuprofen-loaded blend PEO/EC fibers

Electrospinning is a fiber manufacturing technique with the possibility of encapsulating high levels of small molecule drugs while providing controlled release rates. In this study, electrospun blend fibers were produced from polyethylene oxide (PEO) and ethyl cellulose (EC) at various compositions to encapsulate a poorly water-soluble drug of ibuprofen (IBP) at 30% loading. Microscopic evaluation showed smooth and defect-free fiber morphologies for blank and IBP-loaded PEO/EC fibers. The average fiber diameters and fiber yields suggested a potential optimization on the blend fiber composition for the electrospun drug-eluting PEO/EC fibers, where the highest average fiber diameter and fiber yield occurred at 50PEO/50EC fiber composition. Surface wettability studies demonstrated the effects on surface hydrophobicity from blend fibers of water-soluble PEO and hydrophobic EC as well as the incorporation of IBP. In addition, blend fibers containing more PEO promoted the water absorption rates through dissolution of the polymer matrix. Furthermore, results from mechanical testing of the blend fibers showed the highest fiber elastic modulus and tensile strength at fiber compositions in between 75PEO/25EC and 50PEO/50EC, corresponding to the average fiber diameter measurements. The in vitro IBP release rates demonstrated a dependence on the EC compositions supported by the surface wettability and water absorption rate studies. In general, our work demonstrated the ability to electrospin blank and IBP-loaded PEO/EC fibers with the scientific understandings of EC compositions on modulations of fiber physicomechanical properties and in vitro drug release rates. The findings from the work indicated the potential engineering and pharmaceutical applications of electrospun drug-eluting fibers for topical drug delivery.

Study on continuous heat treatment of Aramid III

Aramid III is a high-performance fiber obtained by bulk structure modification based on the molecular structure of Kevlar fiber. Unlike the intermittent heat treatment method of Armos, Aramid III is prepared by continuous heat treatment technology. In this paper, the effects of heat treatment temperature, tension, and speed on fiber properties are studied by orthogonal experimental design. It is concluded that temperature is the most critical factor affecting fiber tensile strength and elastic modulus. The effects of different heat treatment temperatures on the chemical structure, surface morphology, aggregation structure, and the fiber’s mechanical properties and thermal properties are studied. Results show that: the chemical structure of the fiber keeps unchanged and surface morphology of the fibers are similar under the different heat treatment temperatures; the crystallinity of the fiber increases with the increase of temperature; the orientation degree of the fiber increases slightly after heat treatment; with the temperature increasing, the elastic modulus of the fiber increases, the tensile strength and elongation at break increase to a peak and then gradually decrease; the thermal decomposition temperature of the fiber is 533°C, and the decomposition rate is slightly different at different heat treatment temperature.

Humidity influence on mechanics of paper materials: joint numerical and experimental study on fiber and fiber network scale

Paper materials are well-known to be hydrophilic unless chemical and mechanical processing treatments are undertaken. The relative humidity impacts the fiber elasticity, the interfiber joint behavior and the failure mechanism. In this work, we present a comprehensive experimental and computational study on mechanical properties of the fiber and the fiber network under humidity influence. The manually extracted cellulose fiber is exposed to different levels of humidity, and then mechanically characterized using atomic force microscopy, which delivers the humidity dependent longitudinal Young’s modulus. We describe the relation and calibrate the data into an exponential function, and the obtained relationship allows calculation of fiber elastic modulus at any humidity level. Moreover, by using confoncal laser scanning microscopy, the coefficient of hygroscopic expansion of the fibers is determined. We further present a finite element model to simulate the deformation and the failure of the fiber network. The model includes the fiber anisotropy and the hygroscopic expansion using the experimentally determined constants, and further considers interfiber behavior and debonding by using a humidity dependent cohesive zone interface model. Simulations on exemplary fiber network samples are performed to demonstrate the influence of different aspects including relative humidity and fiber-fiber bonding parameters on the mechanical features, such as force-elongation curve, strength and extensibility. Finally, we provide computational insights for interfiber bond damage pattern with respect to different humidity level as further outlook.