Semi-flexible Material Research Articles

Dynamic modulus characteristics and prediction model of semi-flexible materials filled with high-performance cement paste

The dynamic modulus of asphalt mixture is an important factor in the design of asphalt pavement, and many scholars have proposed different models for estimating the dynamic modulus of asphalt mixture, but there are almost no studies on the prediction of the dynamic modulus of semi-flexible materials. In order to analyze and estimate the dynamic modulus of semi-flexible materials, we set up a high-performance cementitious paste (HPCP) semi-flexible material and a reference group Stone Mastic Asphalt (SMA-16) under multiple conditions, first measured its dynamic modulus in the laboratory, and analyzed the dynamic modulus characteristics of the material, and then used the equation the estimation equation proposed by Witczak et al. (Witczak1-37A) as a benchmark to introduce a new parameter, grouting mass ratio (Pb) to develop a Witczak-G prediction model to compare and validate the predicted dynamic modulus with the measured values. The results show that compared with SMA-16, HPCP semi-flexible material exhibits higher dynamic modulus and lower phase angle, and its temperature sensitivity and deformation resistance are significantly better than those of SMA-16. Under the influence of porosity and Pb factor, the dynamic modulus is positively correlated with both factors, and the phase angle increases first and then decreases, showing strong elastic properties. In this paper, we propose a dynamic modulus prediction model based on viscosity and Pb, Witczak-G, which predicts the highest coefficient of determination (R2) of the predicted dynamic modulus as high as 0.99 after initial fitting and validation, which indicates that the Witczak-G model is suitable for predicting the dynamic modulus of semi-flexible materials injected with HPCP.

InkFusion3D: 3D Printing Flexible Sensors with Silicone Rubber and Conductive Ink Materials

With the continuous advancement in current sensor design research, most design schemes still rely on rigid or semi-flexible materials for sensor usage. These interactive devices are increasingly unable to meet the demands of users for adaptability, durability, and biocompatibility, limiting their use in dynamic environments. This paper introduces a novel flexible sensor, InkFusion3D, which is fabricated using a combination of low-cost conductive ink and silicone rubber through 3D printing technology. Due to the significant advantages of InkFusion3D material, such as low cost, durability, good biocompatibility, and wide applicability, it can be customized for various applications to address challenges. The paper elaborates on the manufacturing method of InkFusion3D and its sensing principle upon force application. It also proposes applications in medical and gaming scenarios, such as joysticks, buttons, tangible interaction models, and smart filler materials.

Structural layer applicability of semi-flexible material for rutting resistance: A coupled temperature-mechanical approach.

Semi-flexible material (SFM) is produced by pouring cement grouting material into the asphalt concrete skeleton. It exhibits both characteristics of cement and asphalt, increasing structural stiffness and reducing rutting. Extensive studies have shown that the temperature load coupling effect is one of the leading causes of road rutting. However, few researchers focused on the anti-rutting impact and structural layer applicability of SFM under this effect. Thus, a coupled temperature-mechanical approach was developed based on the finite element (FE) method to simulate the rutting of SFM at different pavement layers and times of the day. During simulation, both standard load and overload were applied to the FE model of pavement. Asphalt mixture and SFM specimens were prepared for essential road performance and dynamic modulus testing. The mechanical properties of SFM and asphalt mixtures at different temperatures were obtained based on the measured data. The structural layer applicability of SFM was revealed by simulating the response of the pavement structure under the combined action of temperature and load. An accelerated pavement test (APT) based validation indicated that the simulation results were accurate. The results show that traditional asphalt pavement and pavement with SFM at the surface and bottom layers tend to exhibit dilative heave adjacent to the wheel load. Using SFM at the middle layer shows a compacted rutting mode, and the pavement has a minimum rise of 51% in rutting depth under the double overloading compared with the pavements with SFM in other layers. It implies that using SFM in the middle layer gives optimal resistance to overload. Considering the depth, form, and resistance of rutting, the SFM in the middle layer of pavement can functionally exert its anti-rutting characteristic.

Material innovation preparation and performance study of semi-flexible pavement materials

Expounding the internal stability and rutting resistance of semi-flexible materials under different porosity can predict the relationship between pavement performance and material porosity. This study designed four porosities of 18%, 20%, 22%, and 25% to prepare the base asphalt mixture. Then the cement mortar was poured into the base asphalt mixture and cured for seven days under ambient temperature and humidity conditions to prepare semi-flexible pavement material. The stress-strain level of semi-flexible pavement(SFP) was analyzed by finite element software under the 20% porosity; the rutting test was used to evaluate the anti-rutting performance of SFP under different porosity. The orthogonal experiment indicated that the optimal ratio of cement mortar was 0.6 water-cement ratio, 15% mineral powder, and 35% sand. The finite element results further showed that the internal shear stress mainly causes the internal displacement and strain of the material. The shrinkage of the cement mortar was 0.168%, and the dynamic stability of SFP with porosity of 18%, 20%, 22%, and 25% were 6058, 7325, 11,053, and 12,353, respectively. The porosity and filling of cement mortar have a positive trend with the anti-rutting performance of semi-flexible pavement materials.

THREE-DIMENSIONAL PRINTING OF CUSTOM SEMIFLEXIBLE AORTIC ROOT MODELS FOR OPERATIVE PLANNING AND SURGICAL PROCTORING OF PERCEVAL VALVE IMPLANTATION

<h3>BACKGROUND</h3> The Perceval Valve (LivaNova, London, United Kingdom) is a rapid-deployment aortic bioprosthesis with a stentless self-expanding design conducive to minimally-invasive approaches. Uptake of this valve may be limited by sizing-related nuances and its unique implantation technique. Three-dimensional modeling and printing of custom patient-specific models can be used for surgical teaching and preoperative planning. Herein, we describe our method for 3D-printing aortic roots using a semi-flexible material and demonstrate their utility for sizing and surgical planning before Perceval Valve Implantation. <h3>METHODS AND RESULTS</h3> Semiflexible models of aortic roots were virtually modelled and 3D-printed from DICOM files containing contrast-enhanced ECG-gated CTA images of the thoracic aorta obtained in patients awaiting surgical aortic valve replacement via right anterior minithoracotomy. Segmentation of the aortic root, annulus and the left ventricular outflow tract was performed using a free, open source, multi-platform software package (http://slicer.org). In Slicer, a three-dimensional shell was generated around the luminogram model and then hollowed out, replicating the interior of the aortic root. After converting the aortic surfaces to standard tessellation language (STL), the models were printed using Thermoplastic Polyurethane (NinjaFlex, NinjaTek, PA,USA) in a direct drive extruder desktop 3D printer (Printrbot Simple Metal, Printrbot, USA). Preliminary model validation was performed in a prospective and blinded manner. Surgeons sized two de-identified aortic roots prior to the patient's operation. Implantation was then performed in the operating room without knowledge of the model sizing. The same size selected in the model corresponded to the size implanted in the operating room. The root models correctly predicted the size of the implanted valve. They also demonstrated the consequences of incorrect sizing (Image). Undersizing resulted in poor leaflet coaptation. Oversizing resulted in pinwheeling or buckling of the Perceval valve, both oversizing-related complications. A prototype holder was developed for simulation of the implantation procedure, including guiding suture placement, traction-countertraction of the sutures and balloon expansion. <h3>CONCLUSION</h3> Custom 3D-printed semiflexible aortic roots allowed for simulation of intraoperative sizing and can reproduce surgically relevant signs of inappropriate sizing, including oversizing (pinwheeling and buckling) and undersizing (suboptimal coaptation). This model will be of use for preoperative planning, sizing and surgical proctoring for the Perceval valve. Custom modeling may accelerate the learning curve associated with this valve and improve uptake for use in minimally invasive aortic valve surgery, combined cases, and patients with small roots.

Study on the Road Performance of Foamed Warm-Mixed Reclaimed Semi-Flexible Asphalt Pavement Material.

Warm-mixed reclaimed asphalt pavement (RAP) technology has been widely studied worldwide as a recycled environmental method to reuse waste materials. However, the aggregate skeleton structure of the warm-mixed reclaimed asphalt mixture is not stable because of the existence of the recycled materials. Warm-mixed recycled semi-flexible pavement material can solve the defects of the above materials. In this study, five different types of open-graded asphalt mixtures containing different contents of RAP were designed, and relevant laboratory tests were conducted to assess the road performance of the warm-mixed recycled semi-flexible pavement material. The test results indicated that the road performance of warm-mixed reclaimed semi-flexible pavement materials has good resistance to rut deformation ability. Furthermore, the materials also had good water stability and fatigue performance. The grey correlation analysis shows that the asphalt binder content has the most significant correlation with the high-temperature stability, and the correlation between RAP content and the fatigue performance was the greatest. Furthermore, the curing age has the most remarkable with the low-temperature crack resistance of the warm-mixed reclaimed semi-flexible material.

Brick-Shaped Antenna Module for Microwave Brain Imaging Systems

In this letter, we describe and validate a microwave antenna designed for an imaging device for the diagnosis and monitoring of cerebrovascular pathologies. The antenna consists of a printed monopole immersed in a parallelepipedic block of semiflexible material with custom-permittivity, which allows to avoid the use of liquid coupling media and enables a simple array arrangement. The “brick” is built with a mixture of urethane rubber and graphite powder. The $-$ 10 dB frequency band of the antenna is 800 MHz—1.2 GHz, in agreement with the device requirements. The designed brick antenna is assessed in terms of power penetration, reflection, and transmission coefficients. To show the performance of the antenna in the relevant application scenario, an experiment has been carried out on an anthropomorphic head phantom, measuring the differential signals between healthy state and hemorrhagic stroke mimicking condition for different antennas positions.

Research on the Influence Factors of Low-Temperature Crack Resistance of Semiflexible Pavement Materials Based on Freezing Test

To study the influence factors of low-temperature performance of semi-flexible pavement materials, a freezing test was conducted, and the cracking temperature was used as the evaluation index to study the influence of asphalt type (90 matrix asphalt, SBS-modified asphalt, TPS high-viscosity modified asphalt), cement-based grout material types (ordinary grout, rubber powder grout, emulsified asphalt grout), and skeleton void ratio (20%, 24%, 28%, 32%) on the low-temperature performance of semi-flexible pavement materials. Results indicate that the freezing test can effectively distinguish the low-temperature crack resistance improvement benefits of semi-flexible pavement materials with different asphalt, cement-based grouting materials, and skeleton void ratios. Cracking temperature can effectively evaluate the low-temperature performance of semi-flexible pavement materials. The substrate void ratio is in the range of 20%-32%, and the cracking temperature changes with the increase in the substrate void ratio, decreasing initially and then rising. When the void ratio is around 24%, the best low-temperature performance of semi-flexible materials is achieved. The improvement effect of the elasticity of grout on the low-temperature crack resistance of semi-flexible pavement materials is obvious; the improvement effect of emulsified asphalt grout on the low-temperature performance of semi-flexible pavement materials is better than that of rubber powder grout. After the modified asphalt is used in the substrate, the cracking temperature is reduced by 31.4%-38.3%, which is much greater than the effect of grouting. At the same time, the elasticity of the base asphalt is more effective than the viscosity increase in improving the low-temperature crack resistance of semi-flexible materials.

Wideband Wearable Antenna for Biomedical Telemetry Applications

This paper presents a wideband, low-profile and semi-flexible antenna for wearable biomedical telemetry applications. The antenna is designed on a semi-flexible material of RT/duroid 5880 (E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 2.2, tanδ = 0.0004) with an overall dimensions of 17 mm × 25 mm × 0.787 mm (0.2λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.29λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.009λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ). A conventional rectangular patch is modified by adding rectangular slots to lower the resonant frequency, and the partial ground plane is modified to enhance the operational bandwidth. The final antenna model operates at 2.4 GHz with a 10-dB bandwidth (fractional bandwidth) of 1380 MHz (59.7 % at the centre frequency of 2.4 GHz). The proposed antenna maintains high gain (2.50 dBi at 2.4 GHz) and efficiency (93 % at 2.4 GHz). It is proved from the simulations and experimental results that the antenna has negligible effects in terms of reflection coefficient, bandwidth, gain, and efficiency when it is bent. Moreover, the antenna is simulated and experimentally tested in proximity of the human body, which shows good performance. The proposed wideband antenna is a promising candidate for compact wearable biomedical devices.

A Novel Flexible Electrotextile 3T MRI RF Coil Array for Carotid Artery Imaging: Design, Characterization, and Prototyping

Magnetic resonance imaging (MRI) is one of the most powerful imaging modality in clinics and is essential for the diagnosis of strokes through carotid artery imaging. The limiting factor for high-quality MRI is the signal-to-noise ratio (SNR) performance of the radio frequency (RF) coils. The current RF surface coils, however, are made of rigid or semiflexible materials with very limited bending properties. As a result, their SNR is limited because they cannot be placed very close to the imaging area, thus receiving noises from parts of the human body, which are not intended to be imaged. Taking advantage of the computerized embroidery and laser cutting technology, in this paper, we utilize electrotextile to design, fabricate, and measure multilayer RF coil array system for 3 Tesla (3T) MRI to improve the SNR performance. The proposed RF coil array system provides an ergonomic and high-performance solution to the 3T MRI systems. A roadmap to systematically design electrotextile RF coil arrays is proposed. RF coil array is characterized to have the accurate resonant frequency, good impedance matching, and low mutual coupling. In addition, magnetic field distribution, bending effects, and human body effects are also discussed. A systematic method to characterize the performance of the electrotextile pattern is studied and used to assist the development and performance characterization. Finally, the high resolution and high SNR images of various kinds of phantoms are obtained using the University of California at Los Angeles (UCLA) Antenna Lab electrotextile coil array after its integration with the 3T MRI scanners at UCLA David Geffen School of Medicine Translational Research Imaging Center. Compared with the conventional surface coil, more than 10 dB SNR increase is observed at the depth of 0.5 cm and 3 dB increase at the depth of 3 cm.

Aerodynamic Assessment of Complex 3D Ice Shape Replications

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;This work introduces an approach allowing the detailed replication of ice shapes generated in icing wind tunnels, with a special focus on complex and strongly varying ice structures, e.g., ice feathers or residual ice stemming from incomplete removal of accreted ice by ice protection systems. 3D-scans are used as an input for the manufacturing process of the ice shape replica. The manufacturing approach itself is based on additive techniques using semi-flexible materials. In contrast to existing replication techniques, this approach allows also clean areas between ice-covered surface locations. In the present paper, a quality assessment based on the comparison of the lift coefficients of real and corresponding artificial ice shapes is presented.&lt;/div&gt;&lt;/div&gt;

Research on Properties of High‐Performance Cement Mortar for Semiflexible Pavement

Cement mortar is one of the most important components of semiflexible pavement materials; however, the effects of cement mortar formulation on the performance and the grouting rate are rarely studied. Therefore, the optimum formulation of high‐performance cement mortar (HPCM) for different types and contents was studied, and the grouting effect of the cement mortar was studied by rutting tests. The results show that polycarboxylate superplasticizer, expansion admixture, and accelerating admixture have different influences on the workability, the strength, and the drying shrinkage of HPCM, and the working ability of HPCM is good by adding these three admixtures. The strength at 7 days is 1.3 to 4 times that of the existing specifications, and the shrinkage rate is less than 0.2. The HPCM has higher early strength, and the strength development is stable in the later period compared with the other research studies. The semiflexible material has better pavement performance when the grouting rate is greater than 90%.

The influence on the durability of semi-flexible airport pavement materials to cyclic wheel load test

In order to find out the influence degree of maternal asphalt mixture void content, the cement slurry water–cement ratio, base layer material and base layer thickness to the durability of cyclic wheel load, the cyclic wheel load test has been conducted with the runway test bench by using 8 groups of semi-flexible pavement (SFP) specimens (300mm×300mm×50mm). The mechanical properties of different maternal asphalt mixture void content (20%, 23%, 26% and 30%) specimens have been tested. Meanwhile, the cyclic wheel load test has been conducted by using 4 groups of SFP specimens with different maternal asphalt mixture void content. According to the Miner cumulative damage theory, the damage variable was adopted and the relationship between loading times and damage variable has been established. The results demonstrate that: the maternal asphalt mixture void content is the most important factor that affects the durability to cyclic wheel load; when the maternal asphalt mixture void content is 26%, the mechanical performance of the semi-flexible material will be superior; the reasonable maternal asphalt mixture void content value for airport pavement engineering should be 26%.

Properties and Application of Semi-Flexible Material in Highway Engineering

This paper studies the Marshall stability, splitting strength and compressive strength testsof the semi-flexible mixture at first, several steps which should be taken to achieve the optimal mixproportion are presented as below: optimal gradation, optimal fluid content, optimal asphalt content,optimal cement content. Secondly introduces systematically the performance, proportioning designand construction process of semi-flexible mixture. Finally as a structural layer can be a goodsolution to the problem of reflecting crack phenomenon of asphalt pavements, aiming at providingreference to its extension and application.