Purpose
The fiber reinforced polymer composites are becoming more critical because of their exceptional mechanical properties and lightweight structures. Fused filament fabrication (FFF) is a ...three-dimensional (3D) printing technique that can manufacture composite structures. However, the effect of impact performance on the structural integrity of FFF made composites compared to the pre-preg composites is a primary concern for the practical usage of 3D printed parts. Therefore, this paper aims to investigate the effect of different processing parameters on the impact performance of 3D printed composites.
Design/methodology/approach
This paper investigates the impact of build orientation, fiber stacking sequence and fiber angle on the impact properties. Two build orientations, three fiber stacking sequences and two different fiber angles have been selected for this study. Charpy impact testing is carried out to investigate the impact energy absorption of the parts. Onyx as a matrix material and two different types of fibers, that is, fiberglass and high strength high temperature (HSHT) fiberglass as reinforcements, are used for the fabrication.
Findings
Results indicate that build orientation and fiber angle largely affect the impact performance of composite parts. The composite part built with XYZ orientation, 0º/90º fiber angle and B type fiber stacking sequence resulted into maximum impact energy. However, comparing both types of fiber reinforcement, HSHT fiberglass resulted in higher impact energy than regular fiberglass.
Originality/value
This study evaluates the damage modes during the impact testing of the 3D printed composite parts. The impact energy absorbed by the composite samples during the impact testing is measured to compare the effect of different processing conditions. The investigation of different types of fiberglass reinforced with Onyx material is very limited for the FFF-based process. The results also provide a database to select the different parameters to obtain the required impact properties.
Omnidirectional broadband absorption of the solar radiation is pivotal to solar energy harvesting and particularly to low-cost non-tracking photovoltaic (PV) technologies. The current work ...numerically examines the utilization of surface arrays composed of Fresnel nanosystems (Fresnel arrays), which are reminiscent of the known Fresnel lenses, for the realization of ultra-thin silicon PV cells. Specifically, the optical and electrical performances of PV cells integrated with Fresnel arrays are compared with those of a PV cell incorporated with an optimized surface array of nanopillars (NP array). It is shown that the broadband absorption of specifically tailored Fresnel arrays can provide an enhancement of ∼20% over that of an optimized NP array. The performed analysis suggests that broadband absorption in ultra-thin films decorated with Fresnel arrays is driven by two light trapping mechanisms. The first is light trapping governed by light concentration, induced by the arrays, into the underlying substrates, which increases the optical coupling between the impinging illumination and the substrates. The second mechanism is light trapping motivated by refraction, as the Fresnel arrays induce lateral irradiance in the underlying substrates, which increases the optical interaction length and hence the overall probability for optical absorption. Finally, PV cells incorporated with surface Fresnel arrays are numerically calculated, with short-circuit current densities (J sc) which are ∼50% higher than that of a PV cell incorporated with an optimized NP array. Also, the effect of increased surface area, due to the presence of Fresnel arrays, and its effect on surface recombination and open-circuit voltage (V oc) are discussed.
Purpose
Liquid crystal display (LCD)-based stereolithography (SLA) technique has been used in drug delivery and fabrication of microfluidic devices and piezoelectric materials. It is an additive ...manufacturing technique where an LCD source has been used as a mask to project the image onto the tank filled with photo curable resin. This resin, when interacted with light, becomes solid. However, critical information regarding the energy absorption during the compression analysis of different components three-dimensional (3D) printed by SLA process is still limited. Therefore, this study aims to investigate the effect of different process parameters on the compressive properties.
Design/methodology/approach
In the present study, the influence of layer thickness, infill density and build orientation on the compression properties is investigated. Four infill densities, that is, 20%, 40%, 60% and 80%; five-layer thicknesses, that is, 50 µm, 75 µm, 100 µm, 150 µm and 200 µm; and two different orientations, that is, YXZ and ZXY, have been selected for this study.
Findings
It is observed that the samples printed with acrylonitrile butadiene styrene (ABS) absorbed higher energy than the flexible polyurethane (FPU). Higher infill density and sample oriented on ZXY absorbed higher energy than sample printed on YXZ orientation, in both the ABS and FPU materials. Parts printed with 80% infill density and 200 µm layer thickness resulted into maximum energy for both the materials.
Originality/value
In this study, two different types of materials are used for the compression analysis using LCD-SLA-based 3D printer. Specific energy absorbed by the samples during compression testing is measured to compare the influence of parameters. The investigation of infill parameters particularly the infill density is very limited for the SLA-based 3D printing process. Also, the results of this study provide a database to select the print parameters to obtain the required properties. The results also compare the specific energy for hard and flexible material for the same combination of the process parameters.
Silicon light funnels are three-dimensional subwavelength structures in the shape of inverted cones with respect to the incoming illumination. Light funnel (LF) arrays can serve as efficient ...absorbing layers on account of their light trapping capabilities, which are associated with the presence of high-density complex Mie modes. Specifically, light funnel arrays exhibit broadband absorption enhancement of the solar spectrum. In the current study, we numerically explore the optical coupling between surface light funnel arrays and the underlying substrates. We show that the absorption in the LF array-substrate complex is higher than the absorption in LF arrays of the same height (~10% increase). This, we suggest, implies that a LF array serves as an efficient surface element that imparts additional momentum components to the impinging illumination, and hence optically excites the substrate by near-field light concentration, excitation of traveling guided modes in the substrate, and mode hybridization.
Purpose
Fused deposition modeling (FDM) is being increasingly used in automotive and aerospace industries because of its ability to produce specimens having difficult geometrical shape. However, ...owing to lack of critical information regarding the reliability and mechanical properties of FDM-printed parts at various designs, the use of 3D printed parts in these industries is limited. Therefore, the purpose of this paper is to investigate the impact of process parameters of FDM on the tensile strength of open-hole specimen printed using in-house-fabricated polylactic acid (PLA).
Design/methodology/approach
In the present study, three process parameters, namely, raster angle, layer thickness and raster width, are selected for investigation of tensile strength. To produce the tensile specimens in the FDM machine, the PLA filament is used which is fabricated from PLA granules using a single-screw extruder. Further, the experimental values are measured and critically analysed. Failure modes under tests are studied using scanning electron microscopy (SEM).
Findings
Results indicate that the raster angle has a significant effect on the tensile strength of open-hole tensile specimen. Specimens built with 0° raster angle, 200-µm layer thickness and 500-µm raster width obtained maximum tensile strength.
Originality/value
In this work, a new concept of testing a plate that has a rectangular shape and a circular hole at the centre is tested. Open-hole tensile test standard ASTM D5766 has been implemented for the first time for the FDM process.
Light‐trapping nanostructures have for decades been researched as a route to enhance the performance of organic solar cells (OSCs). Whereas the power conversion efficiencies (PCEs) of OSCs have ...reached above 18 %, industrially compatible devices made by scalable processing in air, using only nontoxic solvents and materials, have shown significantly lower performance values. Although light‐trapping nanostructures may improve this, the methods for integrating the nanostructures are typically not compatible with industrial scale up. In this work, scalable, industrially compatible, nonfullerene‐based OSCs are developed with integrated light‐trapping nanostructures at the back electrodes in the devices. The OSCs are made by using scalable roll‐to‐roll (R2R) and sheet‐to‐sheet (S2S) processes and the nanostructures are made by using roll‐to‐plate (R2P) nanoimprint lithography. A fully scalable solution is thereby developed for industrially compatible nanostructured OSCs. The nanostructured devices show enhancements in PCE up to 25 % compared to reference cells, owing to an enhancement in the short‐circuit current density (15 %) by enhanced absorption, and improved charge carrier extraction leading to an enhancement in the fill factor (7 %). Optical modeling is utilized to verify the optical effect of the nanostructures. The best devices attain a PCE of 6.5 %, which is the highest reported efficiency for air‐processed slot‐die coated ITO‐free flexible PBDB‐T : ITIC devices, here using nontoxic solvents.
Roll‐to‐roll dreams come through: Roll‐to‐roll (R2R) integration of light‐trapping nanostructures is used to enhance the device performance of R2R‐based organic solar cells. The light‐trapping nanostructures are embedded by using R2R nanoimprint lithography and demonstrate a 25 % power conversion efficiency enhancement over reference cells, in fully scalable and green solvent‐based organic solar cells employing a nonfullerene acceptor system as the active layer.
Fused Deposition Modeling (FDM) is an extrusion-based additive manufacturing technique which growing rapidly due to its ability to fabricate complex parts directly from CAD models. In conjunction ...with its growing applications, the mechanical behavior of the FDM printed part needs thorough investigation for effective application as an end use functional part in various industries such as aerospace, automobile, mold and die, biomedical. Functional applications of FDM printed parts are affected due to their lower mechanical properties compared to injection molded parts. The assessment of the mechanical behavior of the FDM printed part is proved as challenging task due to the wide variety of the process parameters. In the present work, an attempt has been made to experimentally investigate the tensile behavior of FDM printed parts having multi-Infill patterns and different stacking of layer arrangements for different Infill density and raster orientations. Combined patterned parts are printed from two thermoplastic materials, viz. PLA and ABS having six different stacking sequences at three different levels of Infill density (i.e., 30%, 60% and 90%) and two different raster arrangements (i.e., 0° and 45°) and those are mechanically tested to obtain tensile properties. Further, the fractographic analysis was carried out to study various aspects of tensile failure modes for FDM printed multi-infill pattern samples. Combining two different infill patterns and layer stacking sequence improves tensile strength for 45° raster orientation samples and decreases tensile strength for 0° raster orientation samples when compared to a single pattern throughout. For 0° raster orientation, stacking sequence with all the layers are deposited parallel to loading direction offers more strength than multi-infill pattern samples. Whereas for 45° raster orientation, stacking sequence with all the layers parallel to loading direction offers lower strength than multi-infill pattern samples.
Photon management toward the absorption over a wide spectral range of the solar light is important to various absorption‐based photonic devices. The key for high absorption in thin films is the ...ability to “bend the light” from the normal direction into the in‐plane direction. Broadband absorption enhancement is reported in thin films decorated with top surface light funnel arrays (LF arrays) due to strong bending of the light by the arrays into the films, in contrast with excitation of thin films by top surface nanopillar arrays (NP arrays) that is governed by forward scattering. The broadband absorption in the film below the LF array (LF film) is 40% higher than that in a film below an optimized NP array (NP film). Also, the strong light bending by the LF arrays into the underlying film induces strong absorptivity peaks substantially exceeding the Yablonovitch limit for both the LF film and the total array–film complex. Finally, the superior LF film broadband absorption is due to strong light bending from the normal direction into the in‐plane direction which is manifested in efficient generation of mode hybridizations.
The key for high absorption in thin films is the ability to “bend the light” from the normal direction into the in‐plane direction. The broadband absorption in the film below the light funnel array is 40% higher than that in a film below an optimized nanopillar array due to strong bending of the light by the arrays into the films.
A novel approach to designing liquid crystal dimers with high chirality is described. The synthesis, and liquid crystal properties of several new optically active unsymmetrical fluorescent dimers ...belonging to four homologous series are presented. These new oligomesogens possess pro-mesogenic cholesterol as a chiral moiety covalently linked to a fluorescent bent aromatic (chalcone) core through a trimethylene (4-oxybutanoyl)/tetramethylene (5-oxypentanoyl)/pentamethylene (6-oxyhexanoyl)/heptamethylene (8-oxyoctanoyl) central spacer giving rise to four series of chiral dimers. In each series, the chalcone entity is substituted with ethoxy, n-butyloxy to n-dodecyloxy tails, with the aim of learning the relation between the molecular structure and thermotropic behavior. The molecular structures have been characterized by routine characterization techniques. These compounds are fluorescent, as evidenced by recording the emission spectra for two different excitation maxima for some representative compounds. The mesomorphic properties of these dimers have been evaluated by polarizing microscopic and calorimetric studies; for some representative samples, the X-ray diffraction studies has also been carried additionally. Except one, all other compounds exhibit liquid crystal behavior. Within the homologous series comprising trimethylene, pentamethylene, and heptamethylene central spacer, compounds with short hydrocarbon tails exhibit chiral nematic phase and blue phase, whereas the members with intermediate spacer length (but for few exceptions) show the twist grain boundary and/or smectic A phase/s in addition. The thermal behavior of the higher members of these series seems to be dependent on the length of the central spacer. A similar trend was observed for lower and higher homologues of dimers possessing tetramethylene (5-oxypentanoyl, C5, i.e., odd spacer) spacer. Interestingly, the higher homologues of this series were found to exhibit two twist grain boundary phases consecutively, occurring over a relatively wide thermal range with a new phase sequence. Thus, the occurrence of a fluid frustrated phase, in particular, the blue phase in the majority of the dimers, indicates that chirality of these mesogens is high enough such that the helical pitch of the chiral nematic phase is sufficiently short. This behavior can be attributed to the presence of the bent-core chalcone entity in the dimer structure, which enhances the biaxiality and chirality of the system.
Abstract The key characteristics of a DC‐DC converter for a fuel cell (FC) application include higher voltage gain for DC‐link voltage, the continuous and ripple‐free source current that is ...beneficial for FC. This paper proposes a high‐gain DC‐DC converter with continuous and ripple‐free input current. The proposed converter is suitable for integrating fuel cell and photovoltaic (PV) power into an isolated DC microgrid. Modified boost converter with an intermediate capacitor integrated with the cuk converter to achieve high voltage gain and low voltage stress across switches, which also reduces the reverse recovery problem of diodes. A prototype of a 1 kW converter is designed, developed, and analyzed to verify its working principle. The simulation and experimental results for high gain 40/400 V and 1 kW load power, with a DC microgrid of 400 V connected to the proposed converter, are in good harmony and are conforming to the theoretical analysis. The maximum obtained converter efficiency is 96.13%.
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