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.
- Award ID(s):
- 1651957
- PAR ID:
- 10403939
- Date Published:
- Journal Name:
- Polymers
- Volume:
- 15
- Issue:
- 3
- ISSN:
- 2073-4360
- Page Range / eLocation ID:
- 533
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract -
Abstract Here, a novel melt electrospinning method to produce few‐micron and nanometer thick fibers is presented, in which a polymer‐coated wire with a sharp tip is used as the polymer source. The polymer coating is melted via Joule heating of the source wire and extracted toward the target via electrostatic forces. The high viscosity and low charge density of polymer melts lower their stretchability in melt. The method relies on confining the Taylor cone and reducing initial jet diameter via concentrated electrostatic fields as a means to reduce the diameter of fibers. As a result, the initial jet diameter and the final fiber diameter are reduced by an order of magnitude of three to ten times, respectively, using wire melt electrospinning compared to syringe‐ and edge‐based electrospinning. The fiber diameter melt electrospun via this novel method is 1.0 ± 0.9 µm, considerably thinner than conventional melt electrospinning techniques. The generation of thin fibers are explained in terms of the electrostatic field around the wire tip, as obtained from finite element analysis (FEA), which controls the size and shape of the melt electrospun jet.
-
Hydrogels are candidate building blocks in a wide range of biomaterial applications including soft and biohybrid robotics, microfluidics, and tissue engineering. Recent advances in embedded 3D printing have broadened the design space accessible with hydrogel additive manufacturing. Specifically, the Freeform Reversible Embedding of Suspended Hydrogels (FRESH) technique has enabled the fabrication of complex 3D structures using extremely soft hydrogels, e.g., alginate and collagen, by assembling hydrogels within a fugitive support bath. However, the low structural rigidity of FRESH printed hydrogels limits their applications, especially those that require operation in nonaqueous environments. In this study, we demonstrated long-fiber embedded hydrogel 3D printing using a multihead printing platform consisting of a custom-built fiber extruder and an open-source FRESH bioprinter with high embedding fidelity. Using this process, fibers were embedded in 3D printed hydrogel components to achieve significant structural reinforcement (e.g., tensile modulus improved from 56.78 ± 8.76 to 382.55 ± 25.29 kPa and tensile strength improved from 9.44 ± 2.28 to 45.05 ± 5.53 kPa). In addition, we demonstrated the versatility of this technique by using fibers of a wide range of sizes and material types and implementing different 2D and 3D embedding patterns, such as embedding a conical helix using electrochemically aligned collagen fiber via nonplanar printing. Moreover, the technique was implemented using low-cost material and is compatible with open-source software and hardware, which facilitates its adoption and modification for new research applications.more » « less
-
null (Ed.)Cholesteryl ester liquid crystals exhibit thermochromic properties related to the existence of a twisted nematic phase. We formulate ternary mixtures of cholesteryl benzoate (CB), cholesteryl pelargonate (CP), and cholesteryl oleyl carbonate (COC) to achieve thermochromic behavior. We aim to achieve thermochromic fibers by incorporating the liquid crystal formulations into electrospun fibers. Two methods of incorporating the liquid crystal (LC) are compared: (1) blend electrospinning and (2) coaxial electrospinning using the same solvent system for the liquid crystal. For blend electrospinning, intermolecular interactions seem to be important in facilitating fiber formation since addition of LC can suppress bead formation. Coaxial electrospinning produces fibers with higher nominal fiber production rates (g/hr) and with higher nominal LC content in the fiber (wt. LC/wt. polymer assuming all of the solvent evaporates) but larger fiber size distributions as quantified by the coefficient of variation in fiber diameter than blend electrospinning with a single nozzle. Importantly, our proof-of-concept experiments demonstrate that coaxially electrospinning with LC and solvent in the core preserves the thermochromic properties of the LC so that thermochromic fibers are achieved.more » « less
-
Fine polyacrylonitrile (PAN) fibers were produced through a scalable centrifugal spinning process. Sodium chloride (NaCl) was added to the PAN‐dimethylformamide solution to decrease the surface tension and consequently promote a decrease in fiber diameter while increasing the fiber output. The fiber preparation process involved the centrifugal spinning of the PAN‐based solution; developed fibers were stabilized in air at 240°C followed by carbonization at 800°C under a Nitrogen atmosphere. The addition of sodium chloride to the PAN solution led to a 37% decrease in the carbon fiber diameter. The carbon fibers were analyzed by scanning electron microcopy, transmission electron microscopy (TEM), X‐ray diffraction, X‐ray photoelectron spectroscopy (XPS) and electrochemical experiments. The TEM results revealed improved graphitization with the addition of sodium chloride. The XPS analysis showed increased functionality (e.g. O2) on the surface of carbon fibers obtained from PAN/NaCl precursor fibers. A significant improvement was achieved in the electrochemical performance of carbon fibers made from PAN/NaCl precursor fibers compared to those made from pure PAN precursor fibers. POLYM. ENG. SCI., 58:2047–2054, 2018. © 2018 Society of Plastics Engineers