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Carbon fiber reinforced composite materials are often used to protect spacecraft from hypervelocity impacts with micrometeoroids or space debris. Therefore, shock-wave properties of these materials at pressures corresponding to orbital impact velocities are of interest. Experimental studies of shock compressibility of unidirectional carbon fiber polymer composite with longitudinal and transverse fiber orientation relative to the direction of shock-wave propagation have been carried out in the pressure range of up to 200 GPa. Particle velocity profiles on the composite surface-water window interface were recorded with a multichannel laser interferometer. The formation of a two-wave structure with a precursor amplitude from 1.5 to 3 GPa was observed with longitudinally oriented fibers. We show that Hugoniot of the composite material almost does not depend on the orientation of the carbon fibers, except for low pressures, when the particle velocity does not exceed 1 km/s. The graphite/diamond phase transition and the destruction of epoxy resin result in a characteristic kink on the Hugoniot curve with a distinct two-phase state region in the 23–35 GPa pressure range. [ABSTRACT FROM AUTHOR]

The injection molding simulation of short fiber reinforced plastics (SFRP) is time consuming. However, until now it is necessary for predicting the local fiber orientation, to optimize the molding process and to predict the mechanical behavior of the material. This research presents the capabilities of artificial neural networks (NN) in predicting fiber orientation tensor (FOT) during injection molding processes, with a focus on enhancing computational efficiency compared to traditional simulation methods. Three NN architectures are compared based on simulated injection molded plates, with the goal of predicting the effect of the plate geometry on the local fiber orientation. Results indicate that NN outperform the baseline assumption of aligned fibers and demonstrate significant potential for accurate FOT prediction. The computational efficiency of NN, especially during the prediction phase, showcases a reduction in processing time by a factor of 104 compared to traditional simulation methods. This research lays a foundation for further exploration into the feasibility of NN in partly replacing time-consuming simulations for practical applications in injection molding processes. [ABSTRACT FROM AUTHOR]

The aim of the present study is to investigate the static and dynamic responses of damaged curved fiber laminated plates embedded with piezoelectric sensor/actuator. The damage characterized by anisotropic damage formulation is incorporated into the FE model to represent the damaged part of the structure. It is observed that continuous change of fiber orientation in lamina makes VSCL plates less affected by this type of damage and the reduction in natural frequencies can be minimized by adjustment of fiber orientation. Further, an active feedback control approach is adopted to damp out the vibration of the smart damaged VSCL plates. [ABSTRACT FROM AUTHOR]

In this contribution, we are interested in the prediction of the macroscopic thermal conductivity of three-phasic composite materials such as wood fibers. The main idea is to make use of up-scaling such as homogenization to link the pore scale and the sample scale. The studied wood species incorporates three phases: the air, the lumen or matrix and the fibers. Image processing is preformed on a tomographic acquisition with high resolution of some micrometers. It serves to identify the present phases and generates the morphology mesh. The 2D diamond scheme is employed to discretize Fourier's model posed on the segmented morphology. The resulting algorithm is validated using an exact solution. Optimal numerical convergence rates of second order are recorded. The thermal conductivity is therefore estimated following the 2D orthotropic directions. An emphasis is set on the impact of the orientation of fibers on this thermal property. [ABSTRACT FROM AUTHOR]

The R1 (1/T1) map divided by the T2* map (R1/T2* map) draws attention as a high-resolution myelin-related map. However, both R1 and R2* (1/T2*) values demonstrate anisotropy dependent on the white matter (WM) fiber orientation with respect to the static magnetic (B0) field. Therefore, this study primarily aimed to investigate the comprehensive impact of these angular-dependent anisotropies on the R1/T2* value. This study enrolled 10 healthy human volunteers (age = 25 ± 1.3) on the 3.0 T MRI system. For R1/T2* map calculation, whole brain R1 and T2* maps were repeatedly obtained in three head tilt positions by magnetization-prepared two rapid gradient echoes and multiple spoiled gradient echo sequences, respectively. Afterward, all maps were spatially normalized and registered to the Johns Hopkins University WM atlas. R1/T2*, R1, and R2* values were binned for fiber orientation related to the B0 field, which was estimated from diffusion-weighted echo-planar imaging data with 3° intervals, to investigate angular-dependent anisotropies in vivo. A larger change in the R1/T2* value in the global WM region as a function of fiber orientation with respect to the B0 field was observed compared to the R1 and R2* values alone. The minimum R1/T2* value at the near magic-angle range was 18.86% lower than the maximum value at the perpendicular angle range. Furthermore, R1/T2* values in the corpus callosum tract and the right and left cingulum cingulate gyrus tracts changed among the three head tilt positions due to fiber orientation changes. In conclusion, the R1/T2* value demonstrates distinctive and complicated angular-dependent anisotropy indicating the trends of both R1 and R2* values and may provide supplemental information for detecting slight changes in the microstructure of myelin and axons. • R1 and R2* values show anisotropy based on white matter fiber orientation. • The myelin-related R1/T2* map shows more distinctive angular-dependent anisotropy. • The R1/T2* map provided more specific microstructure information in the white matter. [ABSTRACT FROM AUTHOR]

The present paper evaluates the machinability of brazed diamond tools for milling 3D SiC f /C-SiC composites. Defined three milling modes of fiber orientation, transverse, longitudinal, and perpendicular, and surfaces, SA (transverse and longitudinal), SB (transverse and perpendicular), and SC (longitudinal and perpendicular), are chosen to reveal factors influencing milling force and surface integrity. Besides, the removal process mechanism is analyzed through high-speed cameras. The results show that combining fiber orientations influences milling force waveform, whereas surface quality is related to fiber orientation and damage types. The lower cutting speeds obtain better surface quality on SA surfaces, while superior surface quality on SB and SC surfaces is attained with higher cutting speeds. Dominant damage modes include direct fiber breakage and matrix fragmentation. Moreover, the removal process is sequentially matrix cracking and fiber/matrix debonding, fiber breakage, and ultimate failure. Toughening mechanisms of composites containing fiber bridging and fiber pullout are observed during milling. [ABSTRACT FROM AUTHOR]

In this study, a three-point bending test was carried out to determine the mechanical properties of hexagonal-shaped honeycomb core sandwich panels made of jute yarn with two distinct fiber orientations. A custom-made handloom was used to weave the unidirectional jute mat, and hand-layup with the cold press process was applied to fabricate the hexagonal honeycomb sandwich panel. To explore the effectiveness of different natural fibers for producing honeycomb core sandwich panels, a Finite Element Method (FEM) analysis was performed on different natural fibers with different fiber orientations. The resistance to environmental deterioration of bending properties was also investigated. Overall, this work offers perceptive information about the mechanical characteristics of sandwich panels made of jute honeycomb core and their behavior under various climatic circumstances, which may be relevant in a variety of engineering applications. Finally, it is noteworthy that the mechanical properties of jute fibers are anisotropic, which implies that their strength varies with the direction of loading. Sandwich panels with horizontal fiber orientation of hexagonal honeycomb core withstand a 36% higher bending strength than those with vertical fiber orientation. [ABSTRACT FROM AUTHOR]

The repairing and strengthening of concrete structures using external and internal partial confinements are inevitable in the construction industry due to the new standards and rapid developments. The conventional materials and methods of confinement are unable to meet modern safety and functional standards. The fiber-reinforced polymer (FRP) enhances the strength and ductility of deteriorating and new concrete columns by reducing lateral confinement pressure and resistance against seismic shocks. The precise methods of partial confinement are inevitable for effective FRP-concrete bonding, durability, and cost-effectiveness under different loading conditions and to cope with external environmental factors. Predictive modeling and simulation techniques are pivotal for the optimization of confinement materials and methods by investigating the FRP-concrete novel confinement configurations, stress–strain responses, and failure modes. The novel materials and methods for concrete columns' partial confinement lack high compressive strength, ductility, chemical attack resistivity, and different fiber orientation impacts. This review provides an overview of recent confinement materials, novel methods, and advanced modeling and simulation techniques with a critical analysis of the research gaps for partial FRP confinement of concrete columns. The current challenges and future prospects are also presented. [ABSTRACT FROM AUTHOR]

Bending analysis was carried out for a laminated composite porous plate due to sinusoidal loading with various boundary conditions using improved third-order theory. Zero transverse shear stress provided a free surface at the top and bottom of the plate. Also, the authors developed a finite element formulation based on improved third-order shear deformation theory. To circumvent the C1 continuity requirement associated with improved third-order shear deformation theory, a C0 FE formulation was developed by replacing the out-of-plane derivatives with independent field variables. An in-house FORTRAN code was developed for the bending analysis of the laminated porous plate considering a 2D finite element model. The complete thickness of the plate was covered with different porosity patterns. The impacts of various modulus ratios, boundary conditions, thickness ratios, fiber orientation angles, and material parameters were examined for laminated porous plates. There was an 18.8% reduction in deflection in the case of the square plate as compared to rectangular plates, with a porosity value of 0.1, a thickness ratio of 10, and an orientation angle of 0°/90°/0°. According to the current research, adding porosities causes a relatively greater change in deflection rather than stress, thereby aiding in the development of a lightweight structure. [ABSTRACT FROM AUTHOR]

Poly(p-phenylene-2,6-benzobisoxazole) (PBO) fiber is currently one of the best-performing organic fibers; however, its low UV aging resistance limits its use. To improve the UV aging performance of PBO fibers, a novel PBO-Fe-PDA fiber was created by depositing a biomimetic structure of polydopamine (PDA) on the surface of PBO fibers with the transition metal ion Fe3+ as the active center. The surface morphology and elemental composition of PBO-Fe-PDA fibers were investigated. It was revealed that Fe3+ formed a coordination bond structure with the oxazole ring, and PDA was successfully loaded onto the surface of PBO-Fe fibers. After UV aging, the crystallinity and crystallographic orientation of PBO fibers significantly decrease, microcrystals inside the fibers slip, and the size of microvoids in the fibers rises. As a result, the strength of PBO fibers was significantly decreased after UV aging. The anti-UV aging capacity of PBO-Fe-PDA fibers, on the other hand, has been enhanced, as evidenced by a slight drop in crystallinity and crystallographic orientation and a significant decrease in the size growth of internal microvoids in the fibers after UV aging. The tensile strength retention of PBO-Fe-PDA fibers after UV aging increased by 93.13% when compared to PBO fibers without altering the fibers' initial strength. The testing results show that this surface modification method is simple to employ and extends the service life of PBO fibers significantly. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of direct restorations using unidirectional glass fiber orientations and a short-fiber-reinforced composite (SFRC) on the fracture resistance of endodontically treated premolars with mesio-occluso-distal cavities. Ninety double-rooted premolars were selected. Fifteen teeth were left intact/as a control group. The endodontic treatment and cavity preparations of seventy-five teeth were performed and divided into five experimental groups: Resin composite (RC), modified transfixed technique + RC, circumferential technique + RC, cavity floor technique + RC, and SFRC + RC. All teeth were fractured under oblique static loading at a 30° angle using a universal testing machine. The fracture patterns were observed and classified. Data were analyzed with one-way analysis of variance, Pearson chi-square, and Tukey HSD post hoc tests (p = 0.05). The highest fracture strength values were obtained in intact teeth (599.336 N), followed by modified transfixed + RC treated teeth (496.58 N), SFRC + RC treated teeth (469.62 N), RC (443.51 N), circumferential + RC treated teeth (442.835 N), and cavity floor + RC treated teeth (404.623 N) (p < 0.05). There was no significant difference between the RC and the circumferential technique + RC (p > 0.05). Unrepairable fractures were observed at low rates (20%) in the modified transfixed + RC and SFRC + RC teeth, and at higher rates in RC (73.3%), cavity floor + RC (60%), and circumferential + RC (80%) teeth. The application of an SFRC or the modified transfixed technique yielded an improved fracture strength and the fracture pattern of ETPs being restored with a universal injectable composite. [ABSTRACT FROM AUTHOR]

Fiber-reinforced composites (FRPs) are characterized by their lightweight nature and superior mechanical characteristics, rendering them extensively utilized across various sectors such as aerospace and automotive industries. Nevertheless, the precise mechanisms governing the interaction between the fibers present in FRPs and the polymer melt during industrial processing, particularly the manipulation of the flow–fiber coupling effect, remain incompletely elucidated. Hence, this study introduces a geometrically symmetrical 1 × 4 multi-cavity mold system, where each cavity conforms to the ASTM D638 Type V standard specimen. The research utilizes theoretical simulation analysis and experimental validation to investigate the influence of runner and overflow design on the flow–fiber coupling effect. The findings indicate that the polymer melt, directed by a geometrically symmetrical runner, results in consistent fiber orientation within each mold cavity. Furthermore, in the context of simulation analysis, the inclusion of the flow–fiber coupling effect within the system results in elevated sprue pressure levels and an expanded core layer region in comparison to systems lacking this coupling effect. This observation aligns well with the existing literature on the subject. Moreover, analysis of fiber orientation in different flow field areas reveals that the addition of an overflow area alters the flow field, leading to a significant delay in the flow–fiber coupling effect. To demonstrate the impact of overflow area design on the flow–fiber effect, the integration of fiber orientation distribution analysis highlights a transformation in fiber arrangement from the flow direction to cross-flow and thickness directions near the end-of-fill region in the injected part. Additionally, examination of the geometric dimensions of the injected part reveals asymmetrical geometric shrinkage between upstream and downstream areas in the end-of-fill region, consistent with microscopic fiber orientation changes influenced by the delayed flow–fiber coupling effect guided by the overflow area. In brief, the introduction of the overflow area extends the duration in which the polymer melt exerts control in the flow direction, consequently prolonging the period in which the fiber orientation governs in the flow direction (A11). This leads to the impact of fiber orientation on the flow of the polymer melt, with the flow reciprocally affecting the fibers. Subsequently, the interaction between these two elements persists until a state of equilibrium is achieved, known as the flow–fiber coupling effect, which is delayed. [ABSTRACT FROM AUTHOR]

The rheological properties, spinnability, and thermal–oxidative stabilization of high-molecular-weight linear polyacrylonitrile (PAN) homopolymers (molecular weights Mη = 90–500 kg/mol), synthesized via a novel metal-free anionic polymerization method, were investigated to reduce coagulant use, enable solvent recycling, and increase the carbon yield of the resulting carbon fibers. This approach enabled the application of the mechanotropic (non-coagulating) spinning method for homopolymer PAN solutions in a wide range of molecular weights and demonstrated the possibility of achieving a high degree of fiber orientation and reasonable mechanical properties. Rheological analysis revealed a significant increase in solution elasticity (G′) with increasing molecular weight, facilitating the choice of optimal deformation rates for effective chain stretching prior to strain-induced phase separation during the eco-friendly spinning of concentrated solutions without using coagulation baths. The possibility of collecting ~80 wt% of the solvent at the first stage of spinning from the as-spun fibers was shown. Transparent, defect-free fibers with a tensile strength of up to 800 MPa and elongation at break of about 20% were spun. Thermal treatment up to 1500 °C yielded carbon fibers with a carbon residue of ~50 wt%, in contrast to ~35 wt% for industrial radically polymerized PAN carbonized under the same conditions. [ABSTRACT FROM AUTHOR]

Fused deposition modelling (FDM) is a popular additive manufacturing method involving the deposition of a molten filament along a specific path. In this paper, the microstructure and properties of the filament and the printed part are compared to understand the microstructure and property evolution during the printing process. Two commonly used materials Poly-lactic acid (PLA) and carbon fiber-reinforced PLA (CF + PLA) are used for the study. A thorough experimental campaign is undertaken to compare different properties including elastic properties (modulus, ultimate tensile strength, strain to failure), fiber length distribution, fiber orientation distribution, X-ray diffraction (XRD) analysis, and multiscale characterization of damage/mode of failure. The addition of CF reinforcement led to an increase in Young's modulus and a reduction of the tensile strength for both the filament as well as printed coupons. There is extensive microstructural change during the printing process with major fiber breakage and increased misalignment. In general, Young's modulus of the printed part is significantly lower than the filament whereas the strength depends on the printing orientation. Both the filament and printed part display complex modes of failure at multiple length scales. The damage modes for the filament and corresponding printed part are different with a strong dependence on the raster orientation for the latter. XRD confirms somewhat different amorphous behavior for the filament and printed part. [ABSTRACT FROM AUTHOR]

In laminated composite materials design, optimization mainly targets the stacking sequence configuration, which is defined by the lamina thickness and fiber orientations within each layer. Recent studies emphasize the increasing role of Machine Learning in promoting innovative composite designs by facilitating the accurate modeling of essential properties such as strength and stiffness. This study introduces two metamodels that utilize feed-forward artificial neural networks, taking laminate thickness and fiber steering angles as input parameters. The output variables, including strain energy density and the Tsai-Wu failure index, enable the prediction of stacking sequence configurations for laminated materials, a capability confirmed in a case study. The results showcase neural network models with the ability to predict these variables, achieving coefficients of determination above 0.90 for testing data. Consequently, this modeling approach has the potential to be a tool for designers, aiding in decision-making processes for the subsequent optimization of stiffness and strength in structural components made of laminated composite materials. [ABSTRACT FROM AUTHOR]

The present study investigates the effect of internal defects on the composite laminated (CL) plates comprised of two distinct graphite-epoxy materials (AS4/3501-6 and T300/5208). The centrally damaged laminates stacked in two distinct lamination sequences are exposed in thermally varying environments. The CL plates are considered to experience damage in two different combinations of damage parameters. The improved first-order shear deformation theory (IFSDT) based finite element (FE) model is employed to estimate the thermal buckling of CL plates comprised of multiple fiber orientation angles and constrained to C-S-C-S and S-C-S-C boundary restrictions. The implementation of a Radial basis function network (RBFN) surrogate model has demonstrated its potential as a feasible substitute for the computationally demanding Monte-Carlo simulations (MCS) in the context of stochastic exploration. The present investigation scrutinizes the probabilistic properties of diverse materials and their associated damage characteristics. Subsequently, the RBFN-based surrogate model is employed to evaluate the likelihood of failure. [ABSTRACT FROM AUTHOR]

The notch effects on the mechanical behavior of Liquid Silicon Infiltration (LSI) based continuous carbon fiber reinforced silicon carbide (C/C-SiC) was studied. The in-plane (IP) and out-of-plane (OP) flexural properties of notched and unnotched samples with fiber orientations (0°, 45° and 60°) were determined through 3-point-bending (3PB) and single notched beam (SENB) tests. Despite the significant difference in bending modulus, the strength depends only slightly on the fiber orientation and loading direction, which could be explained through the uneven distribution of SiC-matrix within the block-like structure of C/C-SiC. This unique micro-structure also leads to a relatively constant value of notch sensitivity in the IP direction, and the sensitivity to the notch is relatively low for all tested C/C-SiC specimen configurations. Furthermore, due to the large differences of fracture mechanism, the work of fracture (WOF) in the IP direction is significantly smaller than in the OP direction for all fiber orientations. [ABSTRACT FROM AUTHOR]

Manufacturing and investigating metallic‐glass‐fiber‐reinforced epoxies is an important new attempt to present their potential to contribute to the aviation industry. In order to explore the energy absorption in novel CoFeSiB metallic‐glass‐fiber/epoxy resin composites, CoFeSiB/epoxy resin composite cylinders with different fiber volume fractions were prepared by a hot‐pressing method. The amorphism of the metal fibers was analyzed using x‐ray diffraction. The quasi‐static compression tests were performed on different fiber oriented samples with a diameter of 3.6 mm and a height of 7.2 mm. The sample with the fiber orientation [0°/90°] has a higher energy absorption capacity, compared to the one with the fiber orientation [0°/0°]. The dynamic‐ compression tests were performed on the [0°/0°] samples with a diameter of 3 mm and height of 6 mm at different air pressures. The compression fracture surfaces were examined by scanning electron microscope. Then the energy absorption mechanism of the composites was investigated. This study is of great significance for the energy absorption in amorphous metal fiber/epoxy composites. [ABSTRACT FROM AUTHOR]

The present paper highlights the benefits of multiaxially reinforced profiles manufactured by out of die ultraviolet (UV) cured pultrusion. Thanks to the low pulling forces inherent to this technology, we could manufacture a quasi‐isotropic laminate with high fiber content (62% in volume). Even if just one fifth of the reinforcement was arranged longitudinally, the fiber orientation at the ±45° and 90° layers was not distorted. The in‐plane properties of this new balanced reinforcement configuration improved the impact and notched resistance compared to a reference configuration typical of conventional pultrusion, consisting of roving and continuous strand mats. Additionally, the tensile strength achieved in the transversal direction for the new configuration was an order of magnitude higher. Therefore, this novel technology has the potential to broaden the applications targeted by pultrusion to those where multiaxial load cases could be encountered. Highlights: Multiaxially reinforced profiles were made by out of die UV cured pultrusion.These profiles presented enhanced in‐plane properties.Impact resistance was better than that of a typical reinforcement configuration.Notched tensile strength was also improved in both principal directions. [ABSTRACT FROM AUTHOR]

This work aims to study the cutting behavior of biocomposites under different controlled hygrothermal conditions. This investigation choice is motivated by the fact that natural plant fibers such as flax are characterized by their hydrophilicity which makes them able to absorb water from a humid environment. This absorption ability is intensified by increasing the conditioning temperature. The moisture diffusion process affects considerably the mechanical properties of the resulting composite, which causes many issues during the machining operations. In this paper, moisture diffusion, chip form, cutting and thrust forces, and scanning electron microscope (SEM) observations are considered to explore the cutting behavior of flax fiber-reinforced polylactic acid (PLA) depending on the hygrothermal conditioning time. Results reveal that moisture content in the biocomposite is significantly influenced by the conditioning temperature and the fiber orientation. Moisture content and fiber orientation affect both the curling behavior of the removed chip as well as the tool/chip interaction in terms of friction. The machinability of flax fiber-reinforced PLA biocomposites depending on hygrothermal conditioning time is then investigated using SEM analysis in addition to analytical modeling. An analysis of variance is used finally to quantify the observed results. [ABSTRACT FROM AUTHOR]

This paper presents a forced vibration analysis of open doubly curved sandwich panels subjected to a moving constant force. In this paper, the effect of softness of the core is considered by implementing a semi-layerwise theory. To this aim, the first-order shear deformation theory is adopted for the face sheets and a higher-order theory which was obtained based on 3D elasticity theory is considered for the core. The presented formulation is general and as the deepness parameter is accounted in the strain–displacement relations, the formulation can be used for a wide range of deep as well as shallow doubly curved shells. To obtain the dynamic response of the system, the finite element method (FEM) along with the Newmark method is used. The proposed element is a higher-order one with nine nodes and each node has fifteen degrees of freedom. The effect of various parameters such as length-to-thickness ratio, in-plane aspect ratio, boundary conditions, lamination scheme, and fiber orientation angles on the dynamic response of the structure is examined. Additionally, the critical velocity of the force at which the structure experiences maximum dynamic deflection is obtained in each case. The results show that as the length-to-thickness ratio of the structure increases, the dynamic magnification factor curve increases with respect to non-dimensional velocity. This study provides insights into the dynamic behavior of doubly curved sandwich panels with soft cores and can aid in the design of such structures for specific applications. The results of this study can also serve as a benchmark for future studies on the forced vibration behavior of doubly curved sandwich panels. [ABSTRACT FROM AUTHOR]

One fundamental challenge in diffusion magnetic resonance imaging (dMRI) harmonization is to disentangle the contributions of scanner‐related effects from the variable brain anatomy for the observed imaging signals. Conventional harmonization methods rely on establishing an atlas space to resolve anatomical variability and generate a unified inter‐site mapping function. However, this approach is limited in accounting for the misalignment of neuroanatomy that still widely persists even after registration, especially in regions close to cortical boundaries. To overcome this challenge, we propose a personalized framework in this paper to more effectively address the confounding from the misalignment of neuroanatomy in dMRI harmonization. Instead of using a common template representing site‐effects for all subjects, the main novelty of our method is the adaptive computation of personalized templates for both source and target scanning sites to estimate the inter‐site mapping function. We integrate our method with the rotation invariant spherical harmonics (RISH) features to achieve the harmonization of dMRI signals between sites. In our experiments, the proposed approach is applied to harmonize the dMRI data acquired from two scanning platforms: Siemens Prisma and GE MR750 from the Adolescent Brain Cognitive Development dataset and compared with a state‐of‐the‐art method based on RISH features. Our results indicate that the proposed harmonization framework achieves superior performance not only in reducing inter‐site variations due to scanner differences but also in preserving sex‐related biological variability in original cohorts. Moreover, we assess the impact of harmonization on the estimation of fiber orientation distributions and show the robustness of the personalized harmonization procedure in preserving the fiber orientation of original dMRI signals. [ABSTRACT FROM AUTHOR]

Short fiber-reinforced thermoplastic polymers (SFRTPs) are commonly used in various molding methods due to their high specific elasticity and strength. To evaluate the interfacial strength, several determination methods have been proposed, including the interfacial shear strength (IFSS). In previous research, an IFSS evaluation method based on the short beam shear method was proposed. However, this method is only applicable to micrometer-sized fibers with high stiffness levels that are not easily bent. When utilizing cellulose fiber, the interfacial shear strength (IFSS) results frequently exhibit significant deviations. To tackle this issue, we suggest an enhanced experimental technique that employs beam-shaped specimens with welding points based on the short beam shear test. Furthermore, we conducted a three-dimensional analysis of the original method to determine the fiber orientation angle and IFSS. The outcomes were compared with previously reported determinations. The IFSS achieved through the novel method proposed in this paper exhibits high precision and reliability, rendering it suitable for use with soft and flexible fibers. [ABSTRACT FROM AUTHOR]

Parts made through additive manufacturing (AM) often exhibit mechanical anisotropy due to the time-based deposition of material and processing parameters. In polymer material extrusion (MEX), printed parts have weak points at layer interfaces, perpendicular to the direction of deposition. Poly(lactic acid) with chopped carbon fiber was printed on a large-format pellet printer at various extrusion rates with the same tool pathing to measure the fiber alignment with deposition via two methods and relate it to the ultimate tensile strength (UTS). Within a singular printed bead, an X-ray microscopy (XRM) scan was conducted to produce a reconstruction of the internal microstructure and 3D object data on the length and orientation of fibers. From the scan, discrete images were used in an image analysis technique to determine the fiber alignment to deposition without 3D object data on each fiber's size. Both the object method and the discrete image method showed a negative relationship between the extrusion rate and fiber alignment, with −34.64% and −53.43% alignment per extrusion multiplier, respectively, as the slopes of the linear regression. Tensile testing was conducted to determine the correlation between the fiber alignment and UTS. For all extrusion rates tested, as the extrusion multiplier increased, the percent difference in the UTS decreased, to a minimum of 8.12 ± 14.40%. The use of image analysis for the determination of the fiber alignment provides a possible method for relating the microstructure to the meso-property of AM parts, and the relationship between the microstructure and the properties establishes process–structure–property relationships for large-format AM. [ABSTRACT FROM AUTHOR]

Steel fiber‐reinforced concrete (SFRC) has proven to be a suitable structural material for constructing elevated flat slabs, and several existing office and residential buildings, in which SFRC was used for these components, highlighted the positive outcomes from both technical and sustainability perspectives. However, research on the influence of fiber orientation on the flexural performance of SFRC slabs is relatively scarce despite the fact that a number of studies revealed that the use of constitutive models derived from three‐point bending tests on notched beams leads to overestimations of the bearing capacity of statically indeterminate slabs. In this context, this study aims at presenting an extensive experimental program that consisted of testing three SFRC slabs (3.0 × 3.0 × 0.1 m3) subjected to point load under a statically indeterminate test configuration. The testing procedure was followed by the extraction of 88 cores in order to analyze both fiber distribution and orientation by means of a non‐destructive inductive method. The results indicate that lower orientation numbers were observed in cylinders drilled from the slabs in comparison with those observed in the 150 × 150 × 600 mm3 notched reference beams tested to characterize the pre‐ and post‐cracking flexural performance of the SFRC produced. Based on these results, a straightforward design‐oriented approach to compute an orientation factor was proposed and considered to develop the constitutive law used to simulate the structural response of SFRC slabs by means of nonlinear finite element model. The numerical simulation results showed a good agreement with the experimental response, this evidencing that the orientation factor may permit to account for the differences caused by geometric and statistical scale‐induced factors between both the beams used for the SFRC flexural properties characterization and slabs produced with the same SFRC. [ABSTRACT FROM AUTHOR]

The current work examines an experimental and numerical investigation into how steel fiber reinforced concrete (SFRC) slab failure behavior is influenced by fiber orientation by pouring concrete in slab elements. Double‐ended hooked steel fibers with an aspect ratio of 50 were used in varying percentages by volume. Fresh and hardened properties of SFRC were determined based on slump flow, V‐funnel, L‐box, J‐ring test, compression, and flexure tests. The effects of different pouring/casting locations (center and corner), fiber orientation, and fiber content (0, 0.5%, and 1.0%) on the crack pattern of the SFRC slab were observed. While casting, the concrete was allowed to flow through a 30° chute angle to enhance the flowability of concrete. The SFRC slabs without fiber reinforcement undergo brittle failure without forming any prior micro cracks. Slabs with fibers experience ductile failure and show significant post‐cracking strength. The concrete's pouring position only affects the failure crack's inclination for the given workability. In the case of the corner cast slab, the crack was propagated from one edge to the opposite edge of the slab in a straight line and split into two halves. This crack pattern suggested that the fiber distribution was concentrated in half of the slab part in which the pouring corner was located. Adding 0.5% and 1.0% fiber content increased the load‐carrying capacity of slabs by 1.31 and 2.15 times, respectively. In addition to fiber content, the pouring position of concrete also made a difference in the load‐carrying capacity of slabs. The concrete pouring in the slab from the center position with 0.5% and 1.0% fiber content has 17.2% and 40% more load‐carrying capacity compared to the concrete poured in the slab from the corner position with the same fiber content. The deflection and load‐carrying capacity obtained through finite element modeling (FEM) fit the experimental results well. [ABSTRACT FROM AUTHOR]

The venous inflow of each atrial cortex is asymmetric and coupled to geometry and outflow to produce optimal vortices and flow patterns in each chamber. In the right atrium, fiber orientation is dependent on the crista terminals and pectinate muscles, which produce a circumferential squeezing effect to propel blood into the desired direction. The left atrial fiber orientation is a more complex fiber that suits its its geometry and function. This study demonstrates the structural differences between the right and left atria. Background: The right and left atria play important roles in overall cardiac performance, both at rest and during exercise. Atrial dysfunction due to congenital or acquired heart diseases can result in significant disability or death. The prevalence of such conditions has been rising due to the increasing age of the population as well as the progressively larger number of patients with Grown-up congenital heart disease (GUCH). Methods: Left and right atria were collected from rabbits and juvenile sheep, and pattern recognition and image analysis were used to illustrate the microstructure and orientation of the pectinate muscles. Results: The aim of this study is to observe the differences in the structure of the pectinate muscles in both rabbits and sheep. Through image analysis and pattern recognition, we were able to identify the orientation of the patterns that can help produce off-the-shelf patches that are capable of mimicking and/or reproducing most of the functions of normal atrial tissue. Conclusion: The microstructure of the pectinate muscles is unique and provides remarkable functionality to the atria. [ABSTRACT FROM AUTHOR]

Ultrasound-assisted grinding is a new method for compound precision machining of C/SiC with excellent machining characteristics. The electroplated diamond grinding head performs a two-dimensional ultrasonic auxiliary plane grinding single-factor experiment for SiC, 2.5D-C/SiC, and chopped fiber-C/SiC. The influences of linear speed, feed speed, grinding depth, fiber orientation, and fiber structure on the grinding force and surface quality are analyzed in this study. The surface formation and removal mechanisms of C/SiC composites are discussed. The results show that within the parameters of this experiment, the grinding force and surface roughness decrease with the increase in linear speed and increase with the increase in feed speed and grinding depth. The grinding force and roughness can be significantly reduced by applying two-dimensional ultrasound. The maximum percentage reduction in normal and tangential grinding forces was 26.79% and 31.69% when grinding 2.5D-C/SiC along 90° fiber orientation. The maximum percentage of surface roughness reduction was 37.93% when 2.5D-C/SiC was ground along a 90° fiber orientation. The influence of fiber orientation on the two types of C/SiC grinding force is the same, and both are satisfied that the grinding force is highest in the 45° fiber orientation, second highest in the 90° fiber orientation, and lowest in the 0° fiber orientation. The effect of fiber orientation on the roughness of 2.5D-C/SiC is as follows: the surface roughness is highest at 45° fiber orientation, second highest at 90° fiber orientation, and lowest at 0° fiber orientation. The effect of fiber orientation on the roughness of short-cut fiber-C/SiC is as follows: the surface roughness is highest at 0° fiber orientation, second highest at 45° fiber orientation, and lowest at 90° fiber orientation. The effect of fiber structure on grinding force is as follows: Under the same machining conditions, the grinding forces are highest on SiC, second highest on short-cut fiber-C/SiC, and lowest on 2.5D-C/SiC. The effect of fiber structure on surface roughness is as follows: Under the same machining conditions, the surface roughness is highest on short-cut fiber-C/SiC, second highest on 2.5D-C/SiC, and lowest on SiC. [ABSTRACT FROM AUTHOR]

In this work, we compared thermal conductivities of polypropylene fibers and fibrils. The polypropylene fibers were melt spun, and oriented by solid-state drawing. Both wide-angle X-ray scattering and sonic velocity measurements were performed to determine the orientation of fibers. The thermal conductivities of fibers were measured via direct electrical heating method, and that of fibrils were measured via thermal bridge method. Our results show that the thermal conductivity of polypropylene fibers increases linearly with their sonic velocity. This suggests we can use the sonic velocity to characterize the thermal conductivity of semicrystalline polymers. Our results also indicate the average thermal conductivity of fibrils is close to that of fibers. This implies that the low thermal conductivity of polymer fibers is due to the low thermal conductivity of fibrils, instead of thermal resistance between fibrils. [ABSTRACT FROM AUTHOR]

A novel approach for microstructure reconstruction using artificial intelligence (MR-AI) was proposed to nondestructively measure the through-thickness average stochastic fiber orientation distribution (FOD) in a prepreg platelet molded composite (PPMC) plate. MR-AI approach uses thermal strain components on the surfaces of a PPMC plate as input to the deep learning model, which allows to predict a distribution of local through-thickness average fiber orientation state in the entire PPMC volume. The experimental setup with a heating stage and digital image correlation (DIC) was used to measure thermal strains on the surface of the PPMC plate. Optical microscopy was then used to measure FOD in the cross section of the PPMC plate. FOD measurements from optical microscopy imagery compared favorably with FOD prediction by MR-AI. The proposed methodology opens the opportunity for rapid, nondestructive inspection of manufacturing-induced FOD in molded composites. [ABSTRACT FROM AUTHOR]

Carbon fiber-reinforced silicon carbide matrix composites (C f /SiCs) are extensively utilized in the field of aviation and aerospace because of their superior mechanical qualities. However, it is difficult to machine high-quality small holes on them. To investigate the characteristics of micro-drilling on C f /SiCs, the polycrystalline diamond (PCD) tool was used to machine holes on the in-plan and out-of-plan surfaces of C f /SiC composites. The drilling force, the hole morphology and quality were explored. The mechanisms of material removal and tool wear were studied. The size effect during the micro-drilling process was also investigated. The outcomes showed that the out-of-plane drilling process yielded more thrust force and torque than the in-plane drilling process. The main forms of damage at the hole entrance and exit are tearing and burrs during in-plane drilling. The damage is mainly in the form of edge breaking caused by debonding and fracture of longitudinal fiber during out-of-plane drilling. The surface defects of the hole exit and entrance during out-of-plane drilling are fewer than those during in-plane drilling. The roundness errors of holes during in-plane drilling are fewer than those during out-of-plane drilling. Additionally, the surface roughness of the hole wall during in-plane drilling is less. Besides, brittle and ductile removal areas were observed at different fiber orientation angles (FOA). Furthermore, the rapid rise in specific cutting energy and the deterioration of surface quality when the feed rate is much smaller than the cutting edge proves the presence of the size effect. A new observation was that the abrasive wear of the flank face and chisel edge during out-of-plane drilling was more severe than that of in-plane drilling. [ABSTRACT FROM AUTHOR]

In fiber-reinforced components, the fiber alignment and orientation have paramount influence on the thermo-mechanical properties of the resulting composite, for both short and continuous fiber. Here we present the case of an ultra-refractory matrix intended for extreme environment applications, ZrB 2 , reinforced with 20 vol% and 50 vol% short carbon fibers. In both cases, fibers tend to align perpendicular to the uniaxial pressure applied during shaping and sintering of a pellet, although the fiber tilt across the pellet thickness is difficult to determine. Moreover, for high volume fractions of reinforcement, the spatial distribution of the fibers is heterogeneous and tends to have domains of preferential orientations. We compare the information on the fiber distribution as collected by scanning electron microscopy images, X-ray computed tomography and synchrotron X-ray refraction radiography (SXRR). The three techniques prove to be complementary. Importantly, we demonstrate that SXRR yields the most statistically significant information due to the largest field of view, yet with a sensitivity down to the nanometer, and that can be successfully applied also to heavy matrix materials, such as zirconium boride. [ABSTRACT FROM AUTHOR]

Thin-plies are generally defined as composites with ply thicknesses below 100 μm. These materials are rapidly gaining interest for high-performance applications, for example, the aerospace sector. Many practical techniques have been proposed to prevent delamination and improve the strength of composite laminates. A recent study has shown that the delamination could be postponed by replacing layers of CFRP with thin-ply in a unidirectional composite laminate, a configuration known as hybrid laminates reinforced with thin-plies. Since fiber orientation is known to be one of the most important parameters in composite laminate design, this study investigates the effect of oriented layers of thin-ply or both thin-ply and conventional CFRP in a hybrid laminate under out-of-plane tensile loading. A numerical Representative Volume Element (RVE) model for CFRP and thin-ply was generated, considering the unidirectional [0], cross-ply [45/−45], and [0/90] in order to better understand the effect of angle-plied hybrid composite laminates. Experimental results show that angle-plied composite laminates present higher failure load under out-of-plane tensile loading compared to the unidirectional ones. This can be attributed to the fact that an initiated crack is faced with a significantly more complex crack path in an angle-plied laminate to advance in the through-the-thickness direction. [ABSTRACT FROM AUTHOR]

In this paper, the transverse low-velocity impact behavior of uniaxial and biaxial braided composite tubes is investigated to improve the impact resistance of tubular composite structures and to reveal their energy absorption mechanism. Based on the nonlinear progressive damage model, the finite element method is used for experimental verification and numerical analysis. The composite tubes with different stacking sequences and stacking angles were simulated, and their impact responses were evaluated by the peak load Fmax, the maximum indentation depth αmax and the energy absorption EA. The results show that the numerical simulation results are in good agreement with the experimental data, and can accurately capture the failure behavior in the actual scene. The damage mode of the braided composite circular tube under low-velocity impact load is mainly manifested as matrix cracking and interlayer separation, and the expansion direction of the damaged area is basically consistent with the fiber orientation. The impact resistance depends more on the stacking sequence, while the stacking angle is the main factor affecting the energy absorption. Under reasonable design, the uniaxial/biaxial hybrid braided tube can obtain the best low-velocity impact characteristics. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced silicon carbide ceramic matrix composites (C f /SiC composites) have a wide range of applications in aerospace, nuclear energy, braking systems owing to its excellent mechanical performance. Nevertheless, the hardness, brittleness, heterogeneity, and anisotropy of C f /SiC composites give rise to difficulties in machining them. In addition, the characterization and formation mechanism of surface damage in the grinding of C f /SiC composites have not been fully elucidated. The purpose of this paper is to provide a characterization method for surface damage of C f /SiC composites and an evaluation index for surface edge chipping damage (SECD) through conventional scratching (CS) / ultrasonic vibration assisted scratching (UVAS) tests with single abrasive. Towards revealing the surface damage behavior of C f /SiC composites during scratching, as well as the impact of fiber orientation on surface damage. The findings indicate that main forms of surface damage of C f /SiC composites in single abrasive scratching are fiber breakage, fiber fracture-shedding, fiber fracture, fiber-matrix interface debonding, interface fragmentation, matrix cracking, and matrix microcracks. Further, ultrasonic vibration could help to suppress the SECD, and the SECD factor was smallest when scratching along the perpendicular fiber. Furthermore, the fiber orientation can significantly affect the scratching force and cross-sectional area of scratches on C f /SiC composites via single abrasive scratching. The tangential scratching force was usually smaller as compared to the normal scratching force, and the cross-sectional area of scratches in UVAS is smaller than that in CS. Based on the above findings, this study elucidates the formation and evolution of surface damage after scratching under different fiber orientations, filling the research gap in surface damage under ultrasonic assisted machining of C f /SiC composites and providing technical guidance for the machining. [Display omitted] [ABSTRACT FROM AUTHOR]

A comprehensive test program was performed to experimentally investigate the effect of CFRP strengthening on the axial strength and stability of CFS plain angle short columns subjected to monotonic axial compression. A total of 28 specimens were tested by varying the CFRP strengthening configurations for different column heights. Both uni-directional (CF_UD) and bi-directional (CF_BD) CFRP were considered. The influence of various parameters such as the type of CFRP, fiber orientation, and number of CFRP layers was investigated and discussed in detail. For single layer (ply) of CFRP, CF_UD-0° strengthening configuration resulted in maximum increase of axial capacity by 58.33% and 45.72% (in comparison to bare steel specimens), corresponding to 0.5 m and 1.0 m column lengths respectively. All the bare steel and skin-strengthened specimens failed predominantly due to torsional–flexural buckling mode. Additional layer of CFRP wrapping was found to enhance the axial capacity further and CF_UD-0°/BD was found to possess greater capacity in the case of double layer of CFRP. Adopting cardboard in-fill in addition to CF_UD-0° wrap has prevented the torsional mode of buckling and resulted in a peak increase of axial capacity by 192.55% and 240.61% corresponding to 500 mm and 100 mm long specimens, respectively. [ABSTRACT FROM AUTHOR]

In situ tensile testing in a scanning electron microscope was used to study the effects of fiber orientation and colony boundaries in laser-refined fully eutectic Al–Si and Al–Si–Sr alloys. In Al–Si alloy, the measured tensile stress–strain response in samples from single colonies is highly dependent on the orientation of Si nanofiber relative to the loading direction. Tensile samples with multiple colonies exhibit improved strain hardening but the measured ductility was limited by cracking along inter-eutectic colony boundaries. The Al–Si eutectic alloys, doped with Sr and processed with finer spot size laser beam, exhibit higher yield strength in samples from single colony due to refined fiber diameter and inter-fiber spacing of nanoscale Si fibers. As a consequence, samples with multiple colonies exhibit sliding or cracking at eutectic colony boundaries before significant uniform elongation developed within the colonies. The low ductility of Al–Si–Sr sample could be ascribed to the reduced shear strength of colony boundary induced by Sr element addition. [ABSTRACT FROM AUTHOR]

This study focuses on the mechanical properties of electrospun nanofibrous mats, highlighting the importance of the characteristics of single nanofibers in determining the overall mechanical behavior of the mats. Recognizing the significant impacts of the diameter and structural properties of the nanofibers, this research introduces a novel methodology for deriving the effects of the mechanical properties of single nanofibers on the aggregate mechanical performance of electrospun oriented nanofiber mats. For this purpose, a finite element method (FEM) model is developed to simulate the elastoplastic response of the mats, incorporating the influence of structural parameters on mechanical properties. The validation of the FEM model against experimental data from electrospun polyacrylonitrile (PAN) nanofibers with different orientations demonstrates its effectiveness in capturing the elastic–plastic tensile behaviors of the material and confirms its accuracy in terms of reflecting the complex mechanical interactions within the nanofibrous mats. Through a detailed analysis of how nanofiber diameter, orientation of fibers, length-to-width ratio, and porosity affect the mechanical properties of the mats, this research provides valuable insights for the engineering of nanofibrous materials to meet specific mechanical requirements. These findings improve our understanding of nanofibrous mat structures, allowing for better performance in diverse applications as well as highlighting the critical importance of identifying the properties of single nanofibers and their associated impacts on material design. [ABSTRACT FROM AUTHOR]

Polyvinylidene fluoride (PVDF) nanofiber mats have played a significant role in wearable electronic devices that have been in great demand in recent decades. Although manifold PVDFbased freely stacked or well-aligned nanofiber mats created via the electrospinning process have been demonstrated to achieve multisensory capabilities with high sensitivity and long detection range, rarely have any of them proved their ability with a stable process and accurate processing parameters. In this work, we successfully developed freely stacked and well-aligned PVDF nanofiber mats with diameters ranging from micrometers to nanometers, providing stable performance for wearable electronic devices. Through in-depth investigations into material preparation, electrospinning, and fiber collection processes, we revealed the relationship between the nanofiber morphology, β-phase fraction, and piezoelectric output with various process parameters. Characterized by analytical methods, we have established a mature, reliable nanofiber mat fabrication system capable of mass-producing PVDF nanofibers with the required diameter and consistent properties. At 18 kV voltage and 60% RH humidity, the uniformity of the fiber diameter and β-phase content was maintained in a favorable range. When the drum speed increased to 2000 r/s, the fiber orientation and β-phase content increased. We assembled aligned PVDF nanofiber mats with conductive fabric in a flexible piezoelectric sensor that successfully monitored different body movements and produced an output voltage of 0.1 V. This study provides the necessary process parameters for the large-scale production of high-quality PVDF nanofiber mats and provides clear guidance for beginners in the field of nanofiber mat manufacturing. [ABSTRACT FROM AUTHOR]

A previous study on the pull-off testing of metallized carbon fiber-reinforced polymers (CFRPs) via cold spray showed that better adhesion strengths could be obtained when features such as carbon fibers or surfacing elements were present, by providing potential mechanical interlocking features. In this work, a first approach to determining the effect of the fiber orientation on the deposition and bonding of the metallic coating to the thermoplastic composite substrate is explored. Pure Sn powder was cold sprayed onto two thermoplastic Polyether–Ether–Ketone (PEEK) CFRP substrates, containing carbon fibers with different orientations: one had fibers in the plane of the substrate (unidirectional tape), while the other had fibers mostly perpendicular to the substrate (ZRT film). Characterization of the coatings was performed via scanning electron microscopy (SEM) and confocal microscopy, and some aspects of mechanical testing (namely wear and scratch testing) were carried out to assess the effect of the substrate on the properties of the coatings. A slight improvement of the coating deposition was observed on the sample with the ZRT film, and this was associated with deeper penetration of tin into the substrate, around the carbon fibers, for improved mechanical interlocking. Wear testing did not seem to reveal any differences between both samples. Finally, scratch adhesion tests were performed to qualitatively assess the bonding mechanism at the coating-substrate interface, and while adhesive failure seems to be the main failure mechanism, the coating of the Z sample seems to co-deform with the substrate during testing, which could highlight better adhesion strength. [ABSTRACT FROM AUTHOR]

Ultra-high-performance concrete (UHPC) is an advanced cement-based material with excellent mechanical properties and durability. However, with the improvement of UHPC's compressive properties, its insufficient tensile properties have gradually attracted attention. This paper reviews the tensile properties of steel fibers in UHPC. The purpose is to summarize the existing research and to provide guidance for future research. The relevant papers were retrieved through three commonly used experimental methods for UHPC tensile properties (the direct tensile test, flexural test, and splitting test), and classified according to the content, length, type, and combination of the steel fibers. The results show that the direct tensile test can better reflect the true tensile strength of UHPC materials. The tensile properties of UHPC are not only related to the content, shape, length, and hybrids of the steel fibers, but also to the composition of the UHPC matrix, the orientation of the fibers, and the geometric dimensions of the specimen. The improvement of the tensile properties of the steel fiber combinations depends on the effectiveness of the synergy between the fibers. Additionally, digital image correlation (DIC) technology is mainly used for crack propagation in UHPC. The analysis of the post-crack phase of UHPC is facilitated. Theoretical models and empirical formulas for tensile properties can further deepen the understanding of UHPC tensile properties and provide suggestions for future research. [ABSTRACT FROM AUTHOR]

The demand for fiber-filled polymers has witnessed a significant upswing in recent years. A comprehensive understanding of the local fiber orientation is imperative to accurately predict the mechanical properties of fiber-filled products. In this study, we experimentally investigated the fiber orientation kinetics in uniaxial extensional flows. For this, we equipped a rheometer with a Sentmanat extensional measurement device and with an optical train that allows us to measure the fiber orientation in situ during uniaxial extension using small angle light scattering. We investigated an experimental system with glass fibers for the suspended phase (L / D = 8 − 15), and for the matrix either low density polyethylene, which shows strain hardening in extension, or linear low density polyethylene, which shows no strain hardening. For these two polymer matrices, the fiber orientation kinetics were investigated as a function of fiber volume fraction (ϕ = 1 % , 5%, and 10%) and Weissenberg number (by varying the Hencky strain rate, ϵ ˙ H = 0.01 − 1 s − 1 ). We found that all these parameters did not influence the fiber orientation kinetics in uniaxial extension and that these kinetics can be described by a multiparticle model, based on Jeffery's equation for single particles. Our results show that, in uniaxial extension, fiber orientation is solely determined by the applied strain and that, up to the concentrated regime (ϕ ≈ D / L), fiber-fiber interactions do not influence the fiber orientation. The extensional stress growth coefficient of these composites, which is measured simultaneously with the orientation, shows high agreement with Batchelor's equation for rodlike suspensions. [ABSTRACT FROM AUTHOR]

The development of a comprehensive uterine model that seamlessly integrates the intricate interactions between the electrical and mechanical aspects of uterine activity could potentially facilitate the prediction and management of labor complications. Such a model has the potential to enhance our understanding of the initiation and synchronization mechanisms involved in uterine contractions, providing a more profound comprehension of the factors associated with labor complications, including preterm labor. Consequently, it has the capacity to assist in more effective preparation and intervention strategies for managing such complications. In this study, we present a computational model that effectively integrates the electrical and mechanical components of uterine contractions. By combining a state-of-the-art electrical model with the Hyperelastic Mass-Spring Model (HyperMSM), we adopt a multiphysics and multiscale approach to capture the electrical and mechanical activities within the uterus. The electrical model incorporates the generation and propagation of action potentials, while the HyperMSM simulates the mechanical behavior and deformations of the uterine tissue. Notably, our model takes into account the orientation of muscle fibers, ensuring that the simulated contractions align with their inherent directional characteristics. One noteworthy aspect of our contraction model is its novel approach to scaling the rest state of the mesh elements, as opposed to the conventional method of applying mechanical loads. By doing so, we eliminate artificial strain energy resulting from the resistance of soft tissues' elastic properties during contractions. We validated our proposed model through test simulations, demonstrating its feasibility and its ability to reproduce expected contraction patterns across different mesh resolutions and configurations. Moving forward, future research efforts should prioritize the validation of our model using robust clinical data. Additionally, it is crucial to refine the model by incorporating a more realistic uterus model derived from medical imaging. Furthermore, applying the model to simulate the entire childbirth process holds immense potential for gaining deeper insights into the intricate dynamics of labor. [ABSTRACT FROM AUTHOR]

To enhance the prediction accuracy of forming simulations of carbon fiber unidirectional (UD) thermoset prepregs, particularly the wrinkle predictions, bending behavior of UD prepregs in the forming process needs to be accurately characterized and modelled. In this paper, an improved bending test system was proposed to characterize the bending behavior of UD prepregs at different forming temperatures and loading rates. It is found that both the temperature and the loading rate have significant impact on the bending stiffness of UD prepregs. An obvious nonlinear bending behavior can be noted in the fiber direction. The loading rate sensitivity of bending stiffness in the fiber direction decreases with temperature increasing. To simulate the bending deformation, a superimposed membrane-shell element model was employed to achieve the decoupling of tensile-bending deformation. Membrane element simulated the in-plane tensile and in-plane shear deformations of UD prepregs, while shell element primarily accounted for the bending deformation. Fiber orientation dependent nonlinear bending stiffness was accounted in the model. Deformation simulations were conducted for vertical cantilever bending, horizontal cantilever bending, and compression wrinkling of UD prepregs. Good agreement is noted between simulation and experiment, demonstrating efficiency of the model and validity of measured bending stiffness. [ABSTRACT FROM AUTHOR]

The topology and fiber orientation of fiber-reinforced composite structures must be designed computationally to fully demonstrate their anisotropic mechanical properties. Optimization of the topology and fiber orientation is performed either sequentially or concurrently. In the sequential method, topology optimization is performed first, followed by fiber orientation optimization. This separated optimization process does not consider material anisotropy during the topology optimization process. The concurrent method has the potential to realize better results by considering the anisotropic properties during topology optimization. However, the concurrent method often obtains locally optimal solutions because of material anisotropy in the initial optimization process. A continuation approach for anisotropy, which starts with weak anisotropy and then improves the anisotropy gradually, resolves this issue. This paper proposes a new concurrent optimization that can control the growth of anisotropy. The growth of anisotropy affects the topology, which is used to determine a better structure. Optimization results were obtained serially by varying the growth of anisotropy, which allowed a highly optimal topology and fiber orientation to be explored by considering their anisotropic nature. [ABSTRACT FROM AUTHOR]

The artiodactyl (deer and sheep) calcaneus is a model that helps in understanding how many bones achieve anatomical optimization and functional adaptation. We consider how the dorsal and plantar cortices of these bones are optimized in quasi‐isolation (the conventional view) versus in the context of load sharing along the calcaneal shaft by "tension members" (the plantar ligament and superficial digital flexor tendon). This load‐sharing concept replaces the conventional view, as we have argued in a recent publication that employs an advanced analytical model of habitual loading and fracture risk factors of the deer calcaneus. Like deer and sheep calcanei, many mammalian limb bones also experience prevalent bending, which seems problematic because the bone is weaker and less fatigue‐resistant in tension than compression. To understand how bones adapt to bending loads and counteract deleterious consequences of tension, it is important to examine both strain‐mode‐specific (S‐M‐S) testing (compression testing of bone habitually loaded in compression; tension testing of bone habitually loaded in tension) and non‐S‐M‐S testing. Mechanical testing was performed on individually machined specimens from the dorsal "compression cortex" and plantar "tension cortex" of adult deer calcanei and were independently tested to failure in one of these two strain modes. We hypothesized that the mechanical properties of each cortex region would be optimized for its habitual strain mode when these regions are considered independently. Consistent with this hypothesis, energy absorption parameters were approximately three times greater in S‐M‐S compression testing in the dorsal/compression cortex when compared to non‐S‐M‐S tension testing of the dorsal cortex. However, inconsistent with this hypothesis, S‐M‐S tension testing of the plantar/tension cortex did not show greater energy absorption compared to non‐S‐M‐S compression testing of the plantar cortex. When compared to the dorsal cortex, the plantar cortex only had a higher elastic modulus (in S‐M‐S testing of both regions). Therefore, the greater strength and capacity for energy absorption of the dorsal cortex might "protect" the weaker plantar cortex during functional loading. However, this conventional interpretation (i.e., considering adaptation of each cortex in isolation) is rejected when critically considering the load‐sharing influences of the ligament and tendon that course along the plantar cortex. This important finding/interpretation has general implications for a better understanding of how other similarly loaded bones achieve anatomical optimization and functional adaptation. [ABSTRACT FROM AUTHOR]