Integrating Multiple Materials (MM) into large-scale Additive Manufacturing (AM) is a key for various industrial applications wishing to incorporate site-specific properties into geometrically ...complex designs that are difficult to manufacture with traditional techniques. Printing with multiple materials is typically accomplished by using layers as natural material boundaries, but having the capability to switch between materials within a single layer without pausing would further expand MM possibilities. This study used Cincinnati Incorporated’s Big Area Additive Manufacturing (BAAM) system to explore material transitions with a novel dual-hopper that enables in-situ material blending of a pelletized feedstock. Constructing MM and functionally graded material (FGM) structures requires depositing a specific material composition at a specific geometric location to achieve a desired performance. Furthermore, accurately implementing this with the BAAM’s blended extrusion system requires a thorough understanding of the transition between distinct material compositions. This study characterizes a step-change transition between neat acrylonitrile butadiene styrene (ABS) and carbon fiber-reinforced ABS. Three distinct techniques were compared for analyzing the fiber content, and the transition zone between materials was characterized as a function of transition direction. The transition process was consistent to within 0.7 wt% carbon fiber variation between different layers and prints. The transition between materials was found to be directionally dependent, with ABS to CF/ABS having a transition length of 3.5 m compared to 3.2 m for CF/ABS to ABS. Furthermore, the transition from Material A to Material B was found to be repeatable with a possible variance in transition length of 0.3 m.
The crystal structure of a new compound, Cu3Ho7Sb has been determined from X-ray powder diffraction data using the Rietveld method. The investigated compound crystallizes in the tetragonal space ...group P4/nbm (No. 125) with a new structure type and a = 0.62008(3) nm, c = 0.87807(4) nm and z = 1.
Band topologies of hexaborides CaB6 and EuB6 Li, Zhi; Ning, Shu-Yu; Su, HaiBin ...
Science China. Physics, mechanics & astronomy,
2017, 1-2017, 2017-1-00, 20170101, Volume:
60, Issue:
1
Journal Article
Peer reviewed
In last decades, topological materials 1-3 have attracted lots of research interest. Topological Kondo insulator （TKI） 4, as an exotic quantum state, has been proposed theoretically in two ...hexaborides StuB6 and YbB6, in which there is a d/f（p） band inversion at momentum point X 5. There are lots of experimental work supporting the TKI state and metallic sur- face state in typical Kondo insulator SmB6 6-10. However, more and more experimental results demonstrated that YbB6 is trivial insulator at ambient pressure 11. Under high pres- sure, the band gap of YbB6 will close and the dip band inver- sion can happen under pressure about 15 GPa 12.
Recent studies suggest that concussion may be associated with long-term neurological sequelae. Both linear impact and rotational acceleration have been identified as contributors to concussion and ...traumatic brain injury (TBI). Modern football helmets are designed according to the National Operating Committee on Standards for Athletic Equipment (NOCSAE) standard for protection from linear impact, without consideration of protection from rotational injury. A multidisciplinary team was assembled with expertise in brain injury, computational modeling, and materials engineering to design, fabricate and impact test a novel helmet padding system. A rotational fixture with magnesium headform and linear impactor was constructed using a rotary encoder to enable measurement of
z
axis rotational angle, velocity and acceleration. Helmet padding material designs were evaluated using finite element (FE) computational modeling, fabricated to specification and then impact tested. Models from two different manufacturers were retrofit with prototype pads and then compared with unmodified versions for attenuation of rotational acceleration. The helmets were then tested using a standard NOCSAE drop apparatus and headform for linear acceleration performance. Large-size Riddell Revolution and Schutt ION4D helmets retrofit with prototype padding demonstrated 21.6 and 33.6 % decreased peak
z
axis rotational acceleration following a 3.2 m/s side impact compared with their respective unmodified commercial models (717.7 vs. 914.0 rad/s
2
and 768.4 vs. 1,158.6 rad/s
2
,
p
< 0.0001, respectively). The improved performance effect appeared consistent over at least 50 impacts without evidence of early material degradation or helmet damage. Compared with unmodified versions, drop test performance for hybridized helmets, measured by Peak G and severity index (SI), were comparable for most, but were worse for rear (Riddell Revolution) and side (Schutt ION4D) impact conditions. Rotational acceleration from side impacts may be attenuated by directed helmet design while maintaining acceptable linear impact performance. Future work will focus on optimization and durability testing of prototype padding for larger impacts.
Long-fiber thermoplastic (LFT) composite materials are rapidly expanding in automotive, transportation, and recreational industry. Most of these materials are natural or black in color with a need ...for secondary painting of the manufactured products. Standard organic pigments and dyes are not stable above 250°C and degrade during processing. Alternatively, inorganic pigments are thermally stable to at least 800°C. High-performance inorganic pigments offer resistance to outdoor weathering, chemicals, and acids. However, in fiber-reinforced composites, the pigment causes fiber attrition and thereby shows reduction in strength. This work explores colored inorganic-pigmented LFT composites. The ability to integrate the color in the manufacturing steps eliminates the need for secondary painting. Pigment variables such as particle size, distribution, chemistry, and coatings have been investigated. The article presents the processing and performance envelopes of colored inorganic-pigmented LFTs in comparison with unpigmented standard LFTs.
The crystal structure of a new compound, Cu
5Ho
7Sb has been determined from X-ray powder diffraction data using the Rietveld method. The investigated compound crystallizes in the tetragonal space ...group
P4/
nbm (No. 125) with a new structure type and
a=0.62008(3) nm,
c=0.87807(4) nm and
z=1.
The objective of the research effort is to develop cost-effective high performance thermoplastic composite materials and product forms and manufacturing of structural components for mass transit, ...heavy truck and military transport applications. Thermoplastic composites technologies possess the potential to provide structures with lower cost, lighter weight, and improved performance. This paper discusses an integrated processing and product development approach for select components such as seats, floor segments, and roof cover doors generic to mass transit, heavy transit and military transport. Long fiber thermoplastic (LFT) and continuous thermoplastic fiber forms have been used in processes ranging from extrusion-compression to vacuum thermoforming. About 40-60% weight savings with equivalent or enhanced performance have been achieved in these applications. Process modeling such as fiber/polymer melt flow in the LFT process has also been discussed in this paper.
Thermoplastic based composites have found increasing use in transportation, infrastructure, military, and aircraft applications. Not only do they possess the properties of high specific modulus and ...strength that the thermoset-matrix composites have, but also they have the advantages of high toughness, superior impact resistance, and ease of reshaping and recycling. Superior impact resistance and large volume production potential make thermoplastic composites particularly attractive as structural materials in transportation applications. In this work, a thermoplastic composite body panel and a frame structure for mass transit were designed, analyzed, and manufactured. Sandwich construction was used for the load-bearing body panel with glass fiber reinforced polypropylene (PP) face sheets and PP honeycomb core. The thin-walled frame segment was manufactured using carbon fiber reinforced polyphenylene sulphide (PPS). Solid model design, meshing, and structure analysis were carried out using Pro/Engineer, Hypermesh, and ANSYS, respectively. Verification tests were conducted on the final manufactured parts for comparison with the modeling results. The weight of the frame and body panel were evaluated and compared with the metallic frame structure and body shell. Single diaphragm forming (SDF) was used for manufacturing the glass/PP face sheets and the carbon/PPS frame structure. During the cooling, temperature gradients through the thickness may exist in the composites, especially for semi-crystalline composites with high processing temperatures, which may result in residual stress and affect the properties of final parts. A laboratory scale SDF system was designed and built with a cooling system to investigate temperature gradients. The temperature profile through thickness of laminates with different numbers of prepreg layers and materials is predicted using a heat conduction approach. The experimental data is in a good agreement with the predictions. Various cooling rates used in SDF can alter crystallization behavior and therefore mechanical properties. The non-isothermal crystallization kinetics of carbon/PPS laminates was studied, and a combination of Avrami and Ozawa theory was used successfully to describe the crystallization kinetics. Crystallization activation energy was also determined for the carbon/PPS composite and compared with reported data.
Advances in Condensed Matter Optics Liangyao Chen, Ning Dai, Xunya Jiang, Kuijuan Jin, Hui Liu, Haibin Zhao / Shanghai Jiao Tong University Press
2015, 2014, 2015-01-01, 2014-12-16
eBook
The authors of this book, all with a background in condensed matter physics, have carried out advanced researches in recent years to study the optical and magneto-optical properties of many kinds of ...new functional materials, including metal-based meta materials, narrow-to-wide-band gap semiconductors, thin films, and magnetic and magneto-optical materials by using different types of optical methods and instruments. This book describes some of the more recent progresses and developments in the study of condensed matter optics in both theoretic and experimental fields. It will help readers, especially graduate students and scientists who are studying and working in the nano-photonic field, to understand more deeply the characteristics of light waves propagated in nano-structure-based materials with potential applications in the future.
"Molecular glue" (MG) is a term coined to describe the mechanism of action of the plant hormone auxin and subsequently used to characterize synthetic small molecule protein degraders exemplified by ...immune-modulatory imide drugs (IMiDs). Prospective development of MGs, however, has been hampered by its elusive definition and thermodynamic characteristics. Here, we report the crystal structure of a dual-nanobody cannabidiol-sensing system, in which the ligand promotes protein-protein interaction in a manner analogous to auxin. Through quantitative analyses, we draw close parallels among the dual-nanobody cannabidiol sensor, the auxin perception complex, and the IMiDs-bound CRL4
E3, which can bind and ubiquitinate "neo-substrates". All three systems, including the recruitment of IKZF1 and CK1α to CRBN, are characterized by the lack of ligand binding activity in at least one protein partner and an under-appreciated preexisting low micromolar affinity between the two proteinaceous subunits that is enhanced by the ligand to reach the nanomolar range. These two unifying features define MGs as a special class of proximity inducers distinct from bifunctional compounds and can be used as criteria to guide target selection for future rational discovery of MGs.
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