Search Results (366)

Medical phantoms are essential to imaging calibration, clinician training, and the validation of therapeutic procedures. However, most ultrasound phantoms prioritize acoustic realism while neglecting the viscoelastic and anisotropic properties of fibrous soft tissues. This gap limits their effectiveness in modeling realistic biomechanical behavior, especially in wave-based diagnostics and therapeutic ultrasound. Current materials like gelatine and agarose fall short in reproducing the complex interplay between the solid and fluid components found in biological tissues. To address this, we developed a soft, anisotropic composite whose dynamic mechanical properties resemble fibrous biological tissues such as skin and skeletal muscle. This material enables wave propagation and vibration studies in controllably anisotropic media, which are rare and highly valuable. We demonstrate the tunability of damping and stiffness aligned with fiber orientation, providing a versatile platform for modeling soft-tissue dynamics and validating biomechanical simulations. The phantoms achieved Young’s moduli of 7.16–11.04 MPa for skin and 0.494–1.743 MPa for muscles, shear wave speeds of 1.51–5.93 m/s, longitudinal wave speeds of 1086–1127 m/s, and sound absorption coefficients of 0.13–0.76 dB/cm/MHz, with storage, loss, and complex moduli reaching 1.035–6.652 kPa, 0.1831–0.8546 kPa, and 2.138–10.82 kPa. These values reveal anisotropic response patterns analogous to native tissues. This novel natural fibrous composite system affords sustainable, low-cost ultrasound phantoms that support both mechanical fidelity and acoustic realism. Our approach offers a route to next-gen tissue-mimicking phantoms for elastography, wave propagation studies, and dynamic calibration across diverse clinical and research applications. Full article

Background/Objectives: The transparency and biomechanical properties of the human cornea are governed by the precise organization of collagen fibers. A novel quantitative technique to analyze corneal collagen organization, based on intensity gradient modeling and probability density function (PDF) fitting, is proposed. Methods: Derived from second-harmonic generation (SHG) images, the method calculates image gradients, derives PDFs of gradient orientations, and fits them to Gaussian models. Results: Tested across species and temporal healing stages, this approach is an advantageous alternative to traditional methods like Fourier transform and structure tensor analyses, particularly in noisy or low-contrast conditions. Conclusions: The technique offers a scalable, robust framework suitable for research, clinical diagnostics, and treatment monitoring. Full article

With the growing need for lightweight, durable, and high-performance structures, additively manufactured (AM) polymer composite structures have captured significant attention in the engineering community. These structures offer considerable advantages in various dynamic engineering sectors including automotive, aviation, and military. Thus, this investigation emphasizes the numerical analysis of the dynamic properties and vibration control of AM polylactic acid (PLA) composite structures reinforced with continuous glass fibers (CGFR-PLA) and carbon fibers (CCFR-PLA), with 0°–0° and 0°–90° layer orientations. The findings of this numerical study are compared and validated against earlier published experimental results. Initially, the numerical models were created using the Abaqus CAE 2024, replicating the actual experimental models. The numerical bending modal frequency of each numerical model is determined, and the 0°–0° oriented models exhibited considerably higher values compared to the corresponding 0°–90° models. Significant differences were noted between the numerical and experimental values in the higher modes, mainly due to existence of voids and misalignment in the actual models that were not considered in numerical models. Following this, a numerical amplitude frequency response (AFR) analysis was conducted to observe vibration amplitude variations as a function of frequency. The AFR numerical results demonstrated consistent trends with the experimental results despite differences between the absolute values of both scenarios. Afterwards, vibration amplitude control analysis was performed under the influence of a macro fiber composite (MFC) actuator. The findings from both numerical and experimental cases revealed that vibration control was noticeably higher in 0°–0° oriented structures compared to 0°–90° structures. Experimental models demonstrated higher vibration control effectiveness than the corresponding numerical models. Although significant differences between the numerical and experimental vibration response values were observed in each composite structure, the numerical results exhibited consistent trends with the experiments. This discrepancy is attributed to the challenge of capturing all boundary conditions of the experimental scenario and incorporating them into the numerical simulation. Full article

Short fiber-reinforced polymer composites are extensively used in automotive structural components, such as engine mounts and motor mount brackets, due to their favorable strength-to-weight ratio. For motor mount brackets, accurate structural analysis requires consideration of fiber orientation, as it significantly affects the mechanical behavior of the composite. This study aims to investigate the influence of fiber orientation heterogeneity on the mechanical properties of short fiber-reinforced polymer composites formed by injection molding. The spatial variation of the fiber orientation tensor, which evolves from the gate to the flow end during molding, presents challenges in experimental characterization. To address this, microscale analysis was conducted using injection-molded tensile specimens, followed by mesoscale modeling through representative volume elements (RVEs). Homogenization techniques were applied to predict effective mechanical properties, which were subsequently used to evaluate the performance of actual components at the macroscale. The findings demonstrate the importance of multi-scale modeling in capturing the anisotropic behavior of fiber-reinforced composites and provide a framework for more reliable structural analysis in automotive applications. Full article

During the machining of unidirectional carbon fiber-reinforced polymers (UD-CFRPs), their anisotropic characteristics and the complex cutting conditions often lead to defects such as delamination, burrs, and surface/subsurface damage. This study systematically investigates the effects of different fiber orientation angles (0°, 45°, 90°, and 135°) on cutting force, chip formation, stress distribution, and damage characteristics using a coupled macro–micro finite element model. The model successfully captures key microscopic failure mechanisms, such as fiber breakage, resin cracking, and fiber–matrix interface debonding, by integrating the anisotropic mechanical properties and heterogeneous microstructure of UD-CFRPs, thereby more realistically replicating the actual machining process. The cutting speed is kept constant at 480 mm/s. Experimental validation using T700S/J-133 laminates (with a 70% fiber volume fraction) shows that, on a macro scale, the cutting force varies non-monotonically with the fiber orientation angle, following the order of 0° < 45° < 135° < 90°. The experimental values are 24.8 N/mm < 35.8 N/mm < 36.4 N/mm < 44.1 N/mm, and the simulation values are 22.9 N/mm < 33.2 N/mm < 32.7 N/mm < 42.6 N/mm. The maximum values occur at 90° (44.1 N/mm, 42.6 N/mm), while the minimum values occur at 0° (24.8 N/mm, 22.9 N/mm). The chip morphology significantly changes with fiber orientation: 0° produces strip-shaped chips, 45° forms block-shaped chips, 90° results in particle-shaped chips, and 135° produces fragmented chips. On a micro scale, the microscopic morphology of the chips and the surface damage characteristics also exhibit gradient variations consistent with the experimental results. The developed model demonstrates high accuracy in predicting damage mechanisms and material removal behavior, providing a theoretical basis for optimizing CFRP machining parameters. Full article

This paper analyzed the behavior of polymer composite materials reinforced with randomly oriented short natural fibers (hemp, flax, etc.) subjected to external stresses under quasistatic contact conditions with dry Coulomb friction. We presumed the composite body, a 2D flat rectangular plate, being in frictional contact with a rigid foundation for the quasistatic case. The manuscript proposes the finite element method approximation in space and the finite difference approximation in time. The problem of quasistatic frictional contact is described with a special finite element, which can analyze the state of the nodes in the contact area, and their modification, between open, sliding, and fixed contact states, in the analyzed time interval. This finite element also models the Coulomb friction law and controls the penetrability according to a power law. Moreover, the quasi-static case analyzed allows for the description of the load history using an incremental and iterative algorithm. The discrete problem will be a static and nonlinear one for each time increment, and in the case of sliding contact, the stiffness matrix becomes non-symmetric. The regularization of the non-differentiable term comes from the modulus of the normal contact stress, with a convex function and with the gradient in the sub-unit modulus. The non-penetration condition was achieved with the penalty method, and the linearization was conducted with the Newton–Raphson method. Full article

Infrastructures of access networks that mostly exploit the optical fiber medium effectively utilizing wavelength division multiplexing techniques play a key role in advanced F5G fixed networks. The orbital angular momentum technique is highly promising for use within passive optical networks to further increase transmission capacities. So, the utilization of common network resources in wavelength and optical domains will be more important. The main purpose of this paper is to present an analysis of resource efficiencies for various allocation methods applied in the proposed OAM&WDM-PON architecture with a conventional point-to-multipoint topology. This contribution introduces novel static, dynamic and dynamic customized allocation methods for a proposed network design with the utilization of only passive optical splitters in remote nodes. These WDM and OAM channel allocation methods are oriented towards minimizing the number of working wavelengths and OAM channels that will be used for compliance with customers’ requests for data transmitting in the proposed point-to-multipoint OAM&WDM-PON architecture. For analyzing and evaluating the considered allocation methods, a simulation model related to the proposed P2MP OAM&WDM-PON design realized in the MATLAB (R2022A) programming environment is presented with acquired simulation results. Finally, resource efficiencies of the presented novel allocation methods are evaluated from the viewpoint of application in future OAM&WDM-PONs. Full article

Planetary health is a transdisciplinary concept that erases the dividing lines between individual and community health, and the natural systems that support the wellbeing of humankind. Despite planetary health’s broad emphasis on justice, the promotion of science-based policies, and stated commitments to fairness, equity, and harm reduction, the criminal justice system has largely escaped scrutiny. This seems to be a major oversight, especially because the criminalization of mental illness is commonplace, and the system continues to be oriented around a prescientific compass of retribution and folk beliefs in willpower, moral fiber, and blameworthiness. Justice-involved juveniles and adults are funneled into landscapes of mass incarceration with ingrained prescientific assumptions. In non-criminal realms, such as obesity, there is a growing consensus that folk psychology ideas must be addressed at the root and branch. With this background, the Nova Institute for Health convened a transdisciplinary roundtable to explore the need for a ‘Copernican Revolution’ in the application of biopsychosocial sciences in law and criminal justice. This included discussions of scientific advances in neurobiology and omics technologies (e.g., the identification of metabolites and other biological molecules involved in behavior), the need for science education, ethical considerations, and the public health quarantine model of safety that abandons retribution. Full article

The cure kinetics in frontal polymerization (FP) of short carbon-fiber-reinforced composites are investigated numerically, focusing on the influence of fiber aspect ratio, volume fraction, and orientation. A classical heat conduction equation is used in FP, where the enthalpic reaction generates heat. The heat generation term is expressed in terms of the rate of degree of cure ($\mathrm{d}\mathsf{\alpha }/\mathrm{d}\mathrm{t}$) in thermoset resin. A rate equation of the degree of cure for epoxy is established in terms of a pre-exponential factor, activation energy, Avogadro’s gas constant, and temperature. The cure kinetics parameters for epoxy resin used in this study are determined using the Ozawa method. The numerical model was validated with experimental data. The results reveal that the aspect ratio of fibers has a minimal effect on the polymerization time. The volume percentage of fibers significantly influences the curing time and temperature distribution, with higher fiber volume fractions leading to faster curing due to enhanced heat transfer. Additionally, fiber orientation plays a critical role in cure kinetics, with specific angles facilitating more effective heat transfer, thereby influencing the curing rate and frontal velocity. The results offer valuable insights into optimizing the design and manufacturing processes for high-performance epoxy-based composites through FP, where precise control over curing is critical. Full article

Fused Filament Fabrication (FFF) has become a widely adopted additive manufacturing technology due to its cost-effectiveness, material versatility, and accessibility. However, optimizing process parameters, predicting material behavior, and ensuring structural reliability remain major challenges. This review analyzes state-of-the-art computational methods used in FFF, which are categorized into four main areas: melt flow dynamics, cooling and solidification, thermal–mechanical behavior, and material property characterization. Notably, the integration of Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) has led to improved predictions of key phenomena, such as filament deformation, residual stresses, and temperature gradients. The growing use of fiber-reinforced filaments has further enhanced mechanical performance; however, this also introduces added complexity due to filler orientation effects and interlayer adhesion issues. A critical limitation across existing studies is the lack of standardized experimental validation methods, which hinders model comparability and reproducibility. This review highlights the need for unified testing protocols, more accurate multi-physics simulations, and the integration of AI-based process monitoring to bridge the gap between numerical predictions and real-world performance. Addressing these gaps will be essential to advancing FFF as a precise and scalable manufacturing platform. Full article

In this work, the mechanical properties of jute fiber-reinforced polymers were investigated, considering two manufacturing technologies—wet layups and vacuum-assisted resin infusion—with the aim of developing cost-effective composite materials based on natural fibers. In the manufacturing process, two different types of resins were used, specific to each technology. Specimens measuring 25 mm × 200 mm were cut from the resulting laminates at three orientations (0°, 45° and 90° with respect with the weft orientation), and they were subjected to tensile tests. The results showed that resin infusion yielded superior stiffness and strength values when compared to the wet layup. Multi-scale modeling techniques were applied in order to estimate the properties of the fibers and evaluate the orthotropic properties of the composites, and virtual material models that included orthotropic elasticity and the anisotropic Hill plasticity formulation were developed and evaluated, managing to reproduce the experimental data using finite element analyses with decent accuracy. Full article

In recent years, the rapid development of three-dimensional (3D)-printed continuous fiber-reinforced polymer (CFRP) technology has provided novel strategies for customized manufacturing of high-performance composites. This review systematically summarizes research advancements in material systems, processing methods, mechanical performance regulation, and functional applications of this technology. Material-wise, the analysis focuses on the performance characteristics and application scenarios of carbon fibers, glass fibers, and natural fibers, alongside discussions on the processing behaviors of thermoplastic matrices such as polyetheretherketone (PEEK). At the process level, the advantages and limitations of fused deposition modeling (FDM) and photopolymerization techniques are compared, with emphasis on their impact on fiber–matrix interfaces. The review further examines the regulatory mechanisms of fiber orientation, volume fraction, and other parameters on mechanical properties, as well as implementation pathways for functional designs, such as electrical conductivity and self-sensing capabilities. Application case studies in aerospace lightweight structures and automotive energy-absorbing components are comprehensively analyzed. Current challenges are highlighted, and future directions proposed, including artificial intelligence (AI)-driven process optimization and multi-material hybrid manufacturing. This review aims to provide a comprehensive assessment of the current achievements in 3D printing CFRP technology and a forward-looking analysis of existing challenges, offering a systematic reference for accelerating the transformation of 3D printing CFRP technology from laboratory research to industrial-scale implementation. Full article

The concept of variable-stiffness composites allows the stiffness properties to vary spatially in the material. In the case of fiber-reinforced composites, the mechanical properties of the composite can be improved by tailoring the fiber orientations in a spatially optimal manner. In this paper, the problem of optimal spatial orientation of fibers in a two-dimensional composite structure under in-plane loading is studied, using the strain energy-minimizing method. The fiber orientation is assumed to be constant within each element of the model but varies from element to element. The optimal design problem is solved numerically using a global optimization method based on a genetic algorithm. Some numerical examples illustrate the efficiency and applicability of the method. Full article

As large-scale additive manufacturing advances, the reliable prediction of the structural behavior of FDM-printed composites is becoming increasingly important. However, existing finite element methods often oversimplify the material anisotropy introduced by the printing path. This study proposes a projection-based method that maps toolpath-defined fiber orientations directly into a finite element model to represent anisotropic mechanical behavior. The mechanical properties of printed carbon fiber-reinforced ABS were experimentally characterized in three directions (UDL, UDT, and UD10). The results confirmed strong anisotropy, with elastic moduli ranging from 3.2 to 9.8 GPa and tensile strengths from 20 to 81 MPa. The shear modulus and strength obtained from the 10° off-axis tensile tests were 1.17 GPa and 10.9 MPa, respectively. This directional data enabled the implementation of the FE model of a 20 m-long printed ship structure. The predicted mid-span deflection (2.19 mm) differed by only 5% from the experimental measurement (2.08 mm). While effective, this method may face challenges with highly irregular geometries. Nevertheless, it offers a scalable approach for the accurate simulation of FDM-printed composites. Full article

This study aims to enhance the mechanical and wear properties of AZ91 magnesium alloy by reinforcing it with 23 vol.% short carbon fibers (SCFs) aligned in normal (AZ91C-N) and parallel (AZ91C-P) orientations via squeeze-casting. The microstructure and elemental distribution maps were analyzed using an advanced SEM-EDS system. A response surface methodology (RSM) based on a Face-Centered Composite Design (FCCD) was employed to optimize the properties under varying temperature (20–300 °C) and wear load (1–5 N) conditions. The ultimate compressive strength (UCS), yield strength (YS), reduction in height at fracture (Fr), reduction in height at maximum stress (Sr), volume loss, and wear rate were analyzed and optimized. ANOVA confirmed the significant influence of the experimental parameters. A statistical model was developed, with validation showing deviations less than 0.05. The optimized conditions resulted in a UCS of 253 MPa, a YS of 193 MPa, an Fr of 26.1%, an Sr of 21.7%, a volume loss of 0.066 cm³, and a wear rate of 840 cm³/m. The worn surface and surface roughness were also investigated and discussed. The orientation of SCFs significantly influenced wear resistance and surface roughness. This study demonstrates the effectiveness of RSM in optimizing AZ91-SCF composites for high-performance applications. Full article