Flexible Fiber Research Articles

Influence of a Long Flexible Fiber on the Transport Capability of a Non-Clogging Pump

During the operation of non-clogging pumps, the flexible long fiber is prone to clogging and winding during the flow process, which can result in damage to the non-clogging pump, so a numerical simulation method of a solid–liquid two-phase flow in a non-clogging pump with a flexible long fiber is proposed in this paper. The unsteady numerical simulation of the two-phase flow of a single flexible fiber with different densities, lengths and diameters in a double-blade non-clogging pump was carried out to study the influence of fiber parameters on fiber transport capability. The results show that at a density of 920 kg/m3, 300 kg/m3 and 732 kg/m3, the transport capability of flexible fibers decreases successively, and the transport time T0 is 0.32 s, 0.36 s and 0.48 s, respectively. The transport capability of flexible fibers with a length of 150 mm, 200 mm and 250 mm decreases successively, and the transport time T0 is 0.34 s, 0.48 s and 0.96 s, respectively. The transport time T0 is 0.48 s when the fiber diameter dp is 5 mm. When the fiber diameter dp is 7.5 mm, the transport time T0 is 0.51 s. When the fiber diameter dp is 10 mm, the fiber transport capability of the non-clogging pump decreased significantly, and the transport time T0 is 0.68 s. The fiber length has the most obvious effect on fiber transport capability, followed by the fiber diameter and fiber density.

Targeted detection of Barrett’s neoplasia: A case report

Barrett’s esophagus (BE) is a precursor condition for esophageal adenocarcinoma (EAC). This case report describes the in vivo use of a fluorescently-labeled peptide heterodimer specific for epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor (HER2) to identify residual neoplasia in a 52-year-old female patient with BE. This targeted contrast agent was topically administered after an incomplete endoscopic mucosal resection of high-grade dysplasia with carcinoma in situ. A flexible fiber-coupled multi-modal scanning fiber endoscope was used to capture near-infrared fluorescence images. This instrument was passed through the working channel of a standard upper endoscope for use as an accessory. Increased fluorescence intensity was observed from nodular mucosa as a real-time “red flag” to identify the presence of neoplasia. Pathologic tests were conducted on the resected tissues, confirming the presence of stage T1a EAC. The expression EGFR and HER2 was confirmed by immunohistochemistry ex vivo. These findings support integrated imaging as a potential strategy to detect Barrett’s neoplasia.

Flexible fiber composite functional materials based on Fe-MOFs nanozyme catalytic activity for efficient point-of-use water disinfection

Ensuring clean water sources is crucial for human health and safety. However, in underdeveloped areas and emergency situations, low-energy, convenient water disinfection technologies remain a significant challenge. Herein, a series of Fe-MIL-101@flexible fiber composites were designed and synthesized by in-situ cross-linking growth of Fe-MIL-101 metal–organic framework nanozymes on carboxymethyl cellulose (filter paper, cotton, gauze), as a class of point-of-use (POU) water disinfection modules with antibacterial efficacy, portability and biosecurity. The results show that the preparation method of water disinfection material is universal, and the most convenient Fe-MIL-101@composite carboxymethyl filter paper (Fe-MIL-101@CMFP) is outstanding. The combination of Fe-MIL-101 nanozyme with carboxymethyl filter paper (CMFP) is highly stable, even after 200 mechanical or manual frictions, the MOF particles does not fall off, and its flexibility, mechanical properties and filtration efficiency remain unchanged. Furthermore, Fe-MIL-101@CMFP exhibits remarkable simulated activity of peroxidase and oxidase, generating reactive oxygen species (ROS, •OH and O2•-), which effectively eliminate bacteria. Notably, Fe-MIL-101@CMFP filters have excellent bactericidal capability (about 99%), are equally effective on field water, and have no biosafety concerns. Such Fe-MIL-101@flexible fiber composite material, as a portable POU water disinfection and sterilization functional modules, is expected to solve the problem of distributed water disinfection as well as change the way of obtaining safe drinking water in underdeveloped areas and emergency situations.

High reflectivity and high emissivity integrated double layer coating on the flexible alumina fiber fabric with enhanced heat-dissipation efficiency

High emissivity coatings on hypersonic vehicle surfaces dissipate heat by emitting thermal radiation. While the difficulty of increasing emissivity limits the performance of coatings to improve heat-dissipation of the thermal insulation felt. Herein, a novel high-reflectivity and high-emissivity integrated double-layer coating was developed to enhance the thermal insulation performance of the alumina fiber fabric. The coating comprised of TiO2@SiO2 (T@S) as reflective agent and ZrO2/SiCw (ZSC) as emittance agents, was applied on the surface of alumina fiber fabric (AFF). The reflecting effect of radiation heat from the high reflective agent enhanced the thermal insulation properties of the double-layer coating. In the wavelength range of 0.4–2.5 μm, the average emissivity of the ZSC coating was 0.83 and the average reflectivity of the T@S coating was 0.63. With continuous heating at 1400 °C for 10 min with a butane torch, the temperature on the backside of the T@S–ZSC-coated AFF remained relatively stable at 225 °C, which is notably decreased by 80 °C compared to that of the single-layer ZSC-coated AFF. The tensile strength of AFF with T@S–ZSC coating reached 35 MPa after being heat treated at 1200 °C. Moreover, the bonding strength between the coating and the AFF substrate was measured to be 0.15 MPa. The double-layer coating with high emissivity and reflectivity, along with a flexible AFF substrate, offers a promising solution for addressing the challenging of surface heat-dissipation in hypersonic vehicles.

Enhancement of acoustic properties of carbon fibrous membrane (CFM) by in-situ crystallization of PZT nanogenerators (PENGs) inside the fibers for a low-frequency acoustic energy harvesting

Acoustic energy harvesting (AEH) by a nanostructured membrane has recently gained increasing attention. This study focused on a novel approach for in-situ crystallization of Pb(Zr0.58Ti0.42)O3 (PZT) as a piezoelectric nanogenerator (PENG) inside the carbon fibrous membranes (CFM). The electrospinning process and post-heat treatment were applied to synthesize the CFM-embedded PENG, which benefits from both the flexibility of carbon fibers and the piezoelectric properties of the crystallized PZT. The results indicated that the carbon fibers kept their microstructure over the heat treatment at 250 and 350 °C while the crystallization fraction of PZT increased. The XPS analysis revealed that the CFM embedded by in-situ crystallized PENG had a higher diversity of tetragonal and rhombohedral in comparison with the CFM embedded by the pre-crystallized PENGs. Furthermore, the electrical conductivity, dielectric constant, and ferromagnetic properties of CFM were improved with the incorporation of the in-situ crystallized PENGs. The acoustic studies in the range of 250–2000 Hz under sound pressure of 90 dB revealed that sound absorption performance of CFM was increased by about +35 %. Also, the ability of CFM in the AEH process was enhanced drastically by embedding the PENGs inside the carbon fibers. The maximum harvested electricity at 500 Hz was 5.9 and 13.9 W m−2 by CFM embedded by in-situ crystallized and pre-crystallized PENGs, respectively. The above results exhibit the great potential for the CFM-embedded PENGs to be used in low-frequency AEH applications.

Enhancing hemp fiber performance: insights into chitosan treatment and structural evolution

Hemp fiber, recognized for its eco-friendliness, wide availability, and biodegradability, stands as a renewable resource with promising applications. To fully harness its potential, it is crucial to study the relationship between chitosan concentration and both the mechanical and thermal properties of hemp fiber. Understanding these effects can provide a direction to improve the properties and functionalities of hemp fiber, which are essential for many applications, including textiles and construction and automotive materials. Chitosan is known to enhance the antimicrobial and adsorption properties of fibers by changing the chemical properties of the fiber surface. However, up to now, a very limited number of studies have focused on the exact effect of chitosan on the mechanical and thermal stability properties of hemp fibers. Here, the effect of treatment with different concentrations of chitosan solutions is investigated to enhance the properties of hemp fibers and the treated hemp fibers are characterized. It is found that chitosan solution treatment can effectively improve the various properties of hemp fibers. The chitosan treatment improved the surface roughness of hemp fibers. The tensile strength and flexibility of hemp fibers were enhanced. The CSHF-1.5% sample exhibited the highest tensile strength of 616.11 MPa and the lowest tensile modulus of 15.61 GPa. The fiber swelling rate increased to 24.73% at a chitosan solution concentration of 1.5%. The results of thermogravimetric analysis and differential scanning calorimetry analysis demonstrated the effectiveness of chitosan solution treatment in enhancing the thermal stability of hemp fibers. These findings propose a promising method for a significant modification of hemp fiber's mechanical and thermal stability.

Gold(I)-Thiolate Coordination Polymers as Multifunctional Materials: The Case of Au(I)-p-Fluorothiophenolate.

Gold-sulfur interaction has vital importance in nanotechnologies and material chemistry to design functional nanoparticles, self-assembled monolayers, or molecular complexes. In this paper, a mixture of only two basic precursors, such as the chloroauric acid (HAu(III)Cl4) and a thiol molecule (p-fluorothiophenol (p-HSPhF)), are used for the synthesis of gold(I)-thiolate coordination polymers. Under different conditions of synthesis and external stimuli, five different functional materials with different states of [Au(I)(p-SPhF)]n can be afforded. These gold-thiolate compounds are (i) red emissive, flexible, and crystalline fibers; (ii) composite materials made of these red emissive fibers and gold nanoparticles; (iii) amorphous phase; (iv) transparent glass; and (v) amorphous-to-crystalline phase-change material associated with an ON/OFF switch of luminescence. The different functionalities of these materials highlight the great versatility of the gold(I) thiolate coordination polymers with easy synthesis and diverse shaping that may have great potential as sustainable phosphors, smart textiles, sensors, and phase change memories.

Construction of PVDF-HKUST-1/BiVO4 hybrid electrospun flexible fiber membrane for enhanced piezo-photocatalytic reduction performance of Cr(VI)

For the practical implementation of Cr(Ⅵ) removal, effective and recyclable water treatment technology is essential. Polarized electric fields inside piezoelectric materials have proved to be a promising technique for facilitating photogenerated charge separation. In this work, Z-scheme heterojunction photocatalyst HKUST-1/BiVO4 and organic piezoelectric material PVDF were combined through electrospinning to create a novel flexible fiber PVDF-HKUST-1/BiVO4 (PVDF-HV) piezo-photocatalyst membrane. When the amount of HKUST-1/BiVO4 powder was 2.4% and the diameter of the obtained fiber film was 10 cm, the optimal reduction efficiency can be achieved by the piezoelectric photocatalytic reduction in solution with initial pH=2, and the piezo-photocatalytic efficiency of PVDF-HV reached up to 85.33% within 120 min, which was about 1.35 times and 2.19 times greater than that of single photocatalysis and piezoelectric catalysis, respectively. It successfully promoted photo charge separation based on the piezoelectric field in PVDF and the heterojunction produced between HKUST-1 and BiVO4. This research developed an efficient strategy for multi-path collection and exploitation of natural solar energy and vibration energy to boost photoactivity.

Glucan polysaccharides isolated from Lactarius hatsudake Tanaka mushroom: Structural characterization and in vitro bioactivities

Commercially available mushroom polysaccharides have found widespread use as adjuvant tumor treatments. However, the bioactivity of polysaccharides in Lactarius hatsudake Tanaka (L. hatsudake), a mushroom with both edible and medicinal uses, remains relatively unexplored. To address this gap, five L. hatsudake polysaccharides with varying molecular weights were isolated, named LHP-1 (898 kDa), LHP-2 (677 kDa), LHP-3 (385 kDa), LHP-4 (20 kDa), and LHP-5 (4.9 kDa). Gas chromatography-mass spectrometry, nuclear magnetic resonance, and atomic force microscopy, etc., were employed to determine their structural characteristics. The results confirmed that spherical aggregates with amorphous flexible fiber chains dominated the conformation of the LHP. LHP-1 and LHP-2 were identified as glucans with α-(1,4)-Glcp as the main chain; LHP-3 and LHP-4 were classified as galactans with varying molecular weights but with α-(1,6)-Galp as the main chain; LHP-5 was a glucan with β-(1,3)-Glcp as the main chain and β-(1,6)-Glcp connecting to the side chains. Significant differences were observed in inhibiting tumor cell cytotoxicity and the antioxidant activity of the LHPs, with LHP-5 and LHP-4 identified as the principal bioactive components. These findings provide a theoretical foundation for the valuable use of L. hatsudake and emphasize the potential application of LHPs in therapeutic tumor treatments.

A Highly Sensitive and Stretchable Core-Shell Fiber Sensor for Gesture Recognition and Surface Pressure Distribution Monitoring.

This work reports a highly-strain flexible fiber sensor with a core-shell structure utilizes a unique swelling diffusion technique to infiltrate carbon nanotubes (CNTs) into the surface layer of Ecoflex fibers. Compared with traditional blended Ecoflex/CNTs fibers, this manufacturing process ensures that the sensor maintains the mechanical properties (923% strain) of the Ecoflex fiber while also improving sensitivity (gauge factor is up to 3716). By adjusting the penetration time during fabrication, the sensor can be customized for different uses. As an application demonstration, the fiber sensor is integrated into the glove to develop a wearable gesture language recognition system with high sensitivity and precision. Additionally, the authors successfully monitor the pressure distribution on the curved surface of a soccer ball by winding the fiber sensor along the ball's surface.

Assessment of mechanical behavior of sprayed concrete reinforced with waste tire textile fibers

The primary objective of this research is to assess the mechanical properties of shotcrete or sprayed concrete reinforced with waste tire textile fibers (WTTFs). Shotcrete is extensively employed in civil and mining engineering projects for support systems. This study examines the physical and mechanical characteristics of shotcrete samples, both without fibers and reinforced with WTTFs, including density, water absorption, volume of permeable voids, ultrasonic pulse velocity, uniaxial compressive strength, and splitting tensile strength. The reinforced samples consist of WTTF fibers at 0.5%, 1%, and 1.5% concentrations. Test results demonstrate that the inclusion of waste tire textile fibers enhances the mechanical properties of shotcrete, particularly its deformability and energy absorption capacity. Based on the test outcomes, a 1% fiber concentration is recommended as the most suitable ratio for utilizing waste tire textile fibers in shotcrete. Furthermore, these flexible fibers do not impede shotcrete pumping or spraying capabilities.

The role of flexural particles in the shear flow of pine residue biomass: An experiment-informed DEM simulation study

An experiment-informed discrete particle simulation study was performed to investigate the role of flexural particles in the shear flow of milled pine residues. Physical pine anatomical fraction samples were tested in an FT4 powder rheometer. A chip model for bark/stem chips and a fiber model for needles were proposed for DEM. The FT4 simulations show mixed fibers/chips require higher force and torque to drive shear flow than pure chips or fibers. The mass fraction and flexibility of fibers reveal nonlinear inter-dependency on impacting the shear flow of mixed fibers/chips. Polydisperse fibers well match the needle-rich samples on the flow attributes, while polydisperse mixed fibers/chips agree reasonably with the bark/stem-rich samples. The DEM study indicates that the flowability of pine residue biomass is determined collectively by various material attributes of the anatomical fractions, which must be considered when developing preprocessing methods for conversion-ready biomass with adequate material handling performance.

Impact of optical fiber-based photo-activation on dental composite polymerization

ObjectivesThe study aimed to introduce a novel two-step optical fiber-based photo-activation of dental resin-based composites (RBCs) for reducing polymerization shrinkage stress (PSS). MethodsProposed protocol design – in the first step, two flexible plastic optical fibers connected to a dental light curing unit (LCU), were used as light guides inserted into the filling to initiate low-irradiance polymerization from within; in the second step, fibers were extracted and remaining voids were filled with RBC, followed by conventional high-irradiance curing to finalize polymerization. Three bulk-fill RBCs were tested (Beautifil-Bulk Restorative, Filtek Bulk-fill Posterior, Tetric PowerFill) using tooth cavity models. Three non-invasive examination techniques were employed: Digital Holographic Interferometry, Infrared Thermography, and Raman spectroscopy for monitoring model deformation, RBC temperature change, and degree of conversion (DC), respectively. A control group (for each examined RBC) underwent conventional photo-activation. ResultsThe experimental protocol significantly reduced model deformation by 15 – 35 %, accompanied by an 18 – 54 % reduction in RBC temperature change, emphasizing the impact of thermal shrinkage on PSS. Real-time measurements of deformation and temperature provided indirect insights into reaction dynamics and illuminated potential mechanisms underlying PSS reduction. After a 24-hour dark-storage period, DC outcomes comparable to conventional curing were observed, affirming the clinical applicability of the method. ConclusionsProtocol involving the use of two 1.5 mm fibers in the first step (300 mW/cm2 x 10 s), followed by a second conventional curing step (1000 mW/cm2 x 10 s), is recommended to achieve the desired PSS reduction, while maintaining adequate DC and ensuring efficient clinical application. Clinical SignificanceObtained PSS reduction offers promise in potentially improving the performance of composite restorations. Additionally, leveraging the flexibility of optical fibers improves light guide approach for restorations on posterior teeth. Meanwhile, implementation in clinical practice is easily achievable by coupling the fibers with commercial dental LCUs using the provided plastic adapter.

Flexible piezoelectric sensor based on PAN/MXene/PDA@ZnO composite film for human health and motion detection with fast response and highly sensitive

Polyacrylonitrile (PAN) nanofiber-based flexible piezoelectric sensors are recognized for their applicability in wearable electronic devices, personal health monitoring, and motion detection. This research explores the impact of dual fillers, MXene and polydopamine-modified zinc oxide (PDA@ZnO), on the characteristics of PAN-based piezoelectric composite nanofiber films, including planar zigzag conformation content, dielectric, ferroelectric, piezoelectric, and mechanical properties. By integrating PDA@ZnO as a filler, PAN/MXene/PDA@ZnO-5 (PMPO) piezoelectric sensors were developed, showcasing enhanced piezoelectric sensing capabilities. These sensors achieved a sensitivity of 28.56 V/N across a broad linear range, with superior mechanical stability and durability across 3000 loading–unloading cycles, and exhibited swift response and recovery times of 49 ms and 40 ms, respectively. Furthermore, their unique fiber structure and flexibility, when interfaced with the human body, enable the detection of minute physiological movements and the conversion of varied motions into distinct voltage outputs. Thus, these sensors offer considerable promise for applications in human health monitoring and motion posture correction.

Non-invasive FBG-based contact lens for continuous intraocular pressure monitoring

The intraocular pressure (IOP), or pressure inside the eye, is one of the key indicator for glaucoma diagnosis and treatment. The present work shows the design and fabrication of a non-invasive Fiber Bragg Grating (FBG) based contact lens for continuous IOP monitoring. By employing wet etching to reduce the FBG diameter, FBG based contact lens sensitivity and mechanical flexibility are enhanced. The contact lens is made of an optical fiber with a small core diameter that has an inscribed FBG of length 3 mm and is etched for a length of 40 mm to facilitate coiling the eFBG during fabrication. The soft contact lens was fabricated using flexible thin film technology with a transparent and flexible etched Fiber Bragg Grating (eFBG) integrated within flexible polydimethylsiloxane (PDMS) for sensing corneal deformations brought about by IOP variations. Experimental studies on the bionic eyeball model show that the Bragg wavelength shift is highly linear (r2 = 0.9694), with a very good sensitivity of 49.243 pm/mmHg in the IOP pressure range of 0 to 50 mmHg. Due to its ease of fabricating, simplicity of design, and ability to continuously measure pressure with good repeatability and stability, the proposed sensor thus offers a potential solution for IOP monitoring.

Flexible Piezoresistive Sensors Based on PPy Granule-Anchored Multilayer Fibrous Membranes with a Wide Operating Range and High Sensitivity.

The employment of flexible piezoresistive sensors has sparked growing interest within the realm of wearable electronic devices, specifically in the fields of health detection and e-skin. Nevertheless, the advancement of piezoresistive sensors has been impeded by their limited sensitivity and restricted operating ranges. Consequently, it is imperative to fabricate sensors with heightened sensitivity and expanded operating ranges through the utilization of the appropriate methodologies. In this paper, piezoresistive sensors were fabricated utilizing electrospun polyvinylidene fluoride/polyacrylonitrile/polyethylene-polypropylene glycol multilayer fibrous membranes anchored with polypyrrole granules as the sensing layer, while electrospun thermoplastic polyurethane (TPU) fibers were employed as the flexible substrate. The sensitivity of the sensor is investigated by varying the fiber diameter of the sensing layer. The experimental findings reveal that a concentration of 14 wt % in the spinning solution exhibits high sensitivity (996.7 kPa-1) within a wide working range (0-10 kPa). This is attributed to the favorable diameter of the fibers prepared at this concentration, which facilitates the uniform in situ growth of pyrrole. The highly deformable TPU flexible fibers and multilayer sensing layer structure enable different linear responses across a broad pressure range (0-1 MPa). Furthermore, the sensor demonstrates good cyclic stability and can detect human movements under different pressures. These results suggest that the piezoresistive sensor with a wide operating range and high sensitivity has significant potential for future health monitoring and artificial intelligence applications.

Muscle-inspired stiffness-tunable flexible fiber jamming structure for wearable robots *

Soft robotics have found their tremendous application prospects in wearable robots due to the inherent compliance of soft materials when interacting with human bodies. However, the limited load-bearing and output capabilities impeded their application in real world. Variable stiffness design contributes to tackling this problem by enhancing the overall structural rigidity. Nevertheless, most of current jamming-based variable stiffness structures realize their stiffness enhancement by squeezing discrete rigid elements, resulting in the loss of structural compliance in the high stiffness state, which could significantly reduce the deformability and even injure the individuals when utilized in wearable robots. In this paper, we propose a muscle-inspired stiffness-continuously-adjustable flexible fiber jamming (FFJ) structure for soft wearable robots. The FFJ structure can achieve continuous stiffness-variation by controlling the fiber overlapping length, which maintains stretchability even in the high stiffness state. We provide a theoretical model to analyze the mechanical performance of the proposed FFJ structure with different design parameters, and verify the model experimentally. The preliminary results show that we achieved 9 times of stiffness enhancement of the proposed FFJ structure by controlling the vacuum pressure, and the maximum tensile stiffness is 4.1 N mm−1. We further demonstrated the effectiveness of the proposed FFJ structure on wearable robots in three different working scenarios: active finger rehabilitation, active elbow rehabilitation, and passive trunk support. The results show that the FFJ structure was able to provide controllable impedance force for active finger/elbow rehabilitation, and help support the human body during long-term labor. This work broadens the frontiers of soft wearable robots and leads a way to the future design of soft and strong robots and devices.

SCAMORSA-1: a camber-morphing wind turbine blade with sliding composite skin

Wind turbines form an increasingly important source of renewable and sustainable energy. Traditional rigid wind turbine blades are unable to control the flow of air over their surfaces, resulting in higher loads and lower aerodynamic efficiency at non-optimal wind speeds and angles of attack. This paper presents the design of SCAMORSA-1 (“Sliding CAmber- MORphing Skin Action”), a camber-morphing turbine blade in a Horizontal Axis Wind Turbine (HAWT) for increased aerodynamic efficiency and improved extreme load alleviation. The blade is linearly tapered and comprises three sections: a conventional rigid section, a morphing section, and a fixed blade tip, all covered by functionally graded composite skin. Measured from the root, the rigid section spans 0%-60% of the total blade length and its profile transitions at 20% from SD7062 thick airfoil to the thinner SD7037 airfoil. The rigid section includes carbon fiber composite spars that resist flap-wise bending. The morphing section occupies the next 30% of the span with SD2030 airfoil profile and can seamlessly change camber angle up to 10°. This section is composed of three hybrid ribs connected via two leading-edge composite spars and a trailing-edge synchronizing rod. Each hybrid rib has a solid leading-edge segment connected to a flexible trailing-edge segment via T-slots. The trailing-edge segment, where morphing occurs, is an enhanced version of the corrugated FishBAC design, with hexagonal honeycomb infill that increases the out-of-plane stiffness and allows for morphing deformation without internal buckling. Two of these hybrid ribs have servomotors housed in the leading-edge segment. These integrated actuators in the hybrid ribs actuate flexible carbon fiber ribbons that run through slits in the trailing-edge segment to morph it. At the trailing-edge portion of the morphing section, the composite skin transitions to a thin flexible layer that can slide over the deforming trailing-edge segment via skin sliders. Computational simulations were performed to quantify the performance gains and ensure safe operation of all components. A proof-of-concept model of SCAMORSA-1’s morphing section was manufactured and tested to demonstrate the effectiveness of the design.

A vat photopolymerization process for structures reinforced with spatially steered flexible fibers

We present a modified vat photopolymerization process for realizing novel fiber-reinforced composite parts wherein continuous fibers are selectively positioned and oriented across multiple layers along the build direction. This is in contrast to laminates and fiber-wound parts made by repeating fiber patterns; and additively manufactured parts with fibers inserted a posteriori or co-extruded selectively. Our process endows two benefits to the parts made with it: (i) spatially steered fibers embedded along specific paths inside to increase stiffness and strength; and (ii) in-situ fiber-matrix interface concurrently cured with matrix material as opposed to the matrix-matrix interface that exists in co-extruded fibers. The process is enabled by a robot manipulator that guides the fiber in each layer by incrementally orienting it along the tangential direction to the bespoke path. The robot arm and the end-effector do not obstruct the UV light source as they pull the fiber taut from afar in multiple directions to alleviate the undesirable effects of shadows. The robot arm is integrated with the build platform and the UV projector, and the entire process is automated. Examples that illustrate making parts with single and multiple fibers are presented to show the efficacy of the process and the machine. An example is shown with continuous fibers embedded along a few spatially varying principal-stress-flow paths inside a part to improve its stiffness and strength. An increase of 71 % in stiffness and 90 % in strength of the part is observed at fiber volume fraction as small as 0.39 %.

Energy Absorption Characteristics of Composite Material with Fiber-Foam Metal Sandwich Structure Subjected to Gas Explosion.

Based on the previous research on the energy absorption of foam metal materials with different structures, a composite blast-resistant energy-absorbing material with a flexible core layer was designed. The material is composed of three different fiber materials (carbon fiber, aramid fiber, and glass fiber) as the core layer and foamed iron-nickel metal as the front and rear panels. The energy absorption characteristics were tested using a self-built gas explosion tube network experimental platform, and the energy absorption effects of different combinations of blast-resistant materials were analyzed. The purpose of this paper is to evaluate the performance of blast-resistant materials designed with flexible fiber core layers. The experimental results show that the composite structure blast-resistant material with a flexible core layer has higher energy absorption performance. The work performed in this paper shows that the use of flexible core layer materials has great research potential and engineering research value for improving energy absorption performance, reducing the mass of blast-resistant materials, and reducing production costs. It also provides thoughts for the research of biomimetic energy-absorbing materials.