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In the recent years, automakers have been striving to improve the carbon footprint of their vehicles. Sustainable composites, consisting of natural fibers, and/or recycled polymers have been developed as a way to increase the “green content” and reduce the weight of a vehicle. In addition, recent studies have found that the introduction of synthetic fibers to a traditional fiber composite such as glass filled plastics, producing a composite with multiple fillers (hybrid fibers), can result in superior mechanical properties. The objective of this work was to investigate the effect of hybrid fibers on characterization and material properties of polyamide-6 (PA6)/polypropylene (PP) blends. Cellulose and glass fibers were used as fillers and the mechanical, water absorption, and morphological properties of composites were evaluated. The addition of hybrid fibers increased the stiffness (tensile and flexural modulus) of the composites. Glass fibers reduced composite water absorption while the addition of cellulose fibers resulted in higher composite stiffness. The mechanical properties of glass and cellulose filled PA6/PP composites were optimized at loading levels of 15 wt% glass and 10 wt% cellulose, respectively.

Predicting Remaining Useful Life (RUL) of systems has played an important role in various fields of reliability engineering analysis, including in aircraft engines. RUL prediction is critically an important part of Prognostics and Health Management (PHM), which is the reliability science that is aimed at increasing the reliability of the system and, in turn, reducing the maintenance cost. The majority of the PHM models proposed during the past few years have shown a significant increase in the amount of data-driven deployments. While more complex data-driven models are often associated with higher accuracy, there is a corresponding need to reduce model complexity. One possible way to reduce the complexity of the model is to use the features (attributes or variables) selection and dimensionality reduction methods prior to the model training process. In this work, the effectiveness of multiple filter and wrapper feature selection methods (correlation analysis, relief forward/backward selection, and others), along with Principal Component Analysis (PCA) as a dimensionality reduction method, was investigated. A basis algorithm of deep learning, Feedforward Artificial Neural Network (FFNN), was used as a benchmark modeling algorithm. All those approaches can also be applied to the prognostics of an aircraft gas turbine engines. In this paper, the aircraft gas turbine engines data from NASA Ames prognostics data repository was used to test the effectiveness of the filter and wrapper feature selection methods not only for the vanilla FFNN model but also for Deep Neural Network (DNN) model. The findings show that applying feature selection methods helps to improve overall model accuracy and significantly reduced the complexity of the models.

Municipal wastewater sludge, particularly waste activated sludge (WAS), is more difficult to digest than primary solids due to a rate-limiting cell lysis step. The cell wall and the membrane of prokaryotes are composed of complex organic materials such as peptidoglycan, teichoic acids, and complex polysaccharides, which are not readily biodegradable. Physical pretreatment, particularly ultrasonics, is emerging as a popular method for WAS disintegration. The exposure of the microbial cells to ultrasound energy ruptures the cell wall and membrane and releases the intracellular organics in the bulk solution, which enhances the overall digestibility. This review article summarizes the major findings of ultrasonic application in WAS disintegration, and elucidates the impacts of sonic treatment on both aerobic and anaerobic digestion. This review also touches on some basics of ultrasonics, different methods of quantifying ultrasonic efficacy, and some engineering aspects of ultrasonics as applied to biological sludge disintegration. The review aims to advance the understanding of ultrasound sludge disintegration and outlines the future research direction. There is general agreement that ultrasonic density is more important than sonication time for efficient sludge disintegration. Published studies showed as much as 40% improvement in solubilization of WAS following ultrasonic pretreatment. Based on kinetic models, ultrasonic disintegration was impacted in the order: sludge pH > sludge concentration > ultrasonic intensity > ultrasonic density. Both laboratory and full-scale studies showed that the integration of an ultrasonic system to the anaerobic digester improved the anaerobic digestibility significantly.

This study aimed to determine the effect of pretreating defatted soy flakes with ultrasound on soy protein isolate (SPI) yield and functionality. Defatted soy flakes dispersed into water (16%, w/w) were sonicated for 30, 60 and 120 s at ultrasonic amplitudes of 21 and 84 μmpp (peak to peak amplitude in μm), representing low and high power, respectively. The power densities were 0.30 and 2.56 W mL⁻¹, respectively. The SPI yield increased by 13 and 34%, after sonication for 120 s at low and high power, respectively. The sonication of defatted soy flakes for 120 s at the higher power level improved the SPI solubility by 34% at pH 7.0, while decreasing emulsification and foaming capacities by 12 and 26%, respectively, when compared to control SPI. Rheological behavior of the SPI was also modified with significant loss in consistency coefficient due to sonication. Some of these results could be explained by the loss of the protein native state with increased sonication time and power.

This work was conducted to determine if there were any benefits with orbital vibration welding compared to linear vibration welding. The experiments were conducted using standard full‐factorial designs with each process and each material. Four materials, polypropylene/polyethylene copolymer (PP/PE), polycarbonate (PC), acrylonitrile‐butadiene‐styrene (ABS) and Nylon (PA), were studied with each process. The equipment used was a modified Branson VW‐4 with an orbital head that had isolated magnets. The same machine was used to weld with both linear and orbital motions. This was achieved by modifying the controlling parameters of the drive. It was found that compared to linear vibration welding, orbital welding had a reduction of cycle time by 36% and 50% in Phase I and Phase III, respectively. It was also found that orbital welding dissipated 56% and 100% more power than linear vibration welding in Phase I and Phase III, respectively. In addition, it was seen that orbital welding was able to universally join unsupported walls with higher strengths and better consistency compared to linear welding. Other benefits included: a difference in the appearance of weld flash and small increase in weld strength. Some of the limitations of orbital welding that were identified included the effects of disengagement and residual stresses. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

The use of fused deposition modeling (FDM) in printing polymers for various applications has been ever increasing. However, its utilization in printing polymers for high-strength and superior surface finish applications is still a challenge, primarily due to process intrinsic defects, i.e., voids between the layers and the rough exterior arising from unrestrained deposition of molten polymer. This research hypothesizes that application of ultrasonic vibration (USV) post-fabrication could minimize these shortcomings. For this investigation, ASTM D638 Type IV samples were FDM-printed using poly(lactic) acid (PLA). Through screening experiments, an optimized set of ultrasonic parameters was determined. Then, the effect of both-sided ultrasonic application was characterized. Subsequently, the impact of USV on the samples’ physical, tensile, and morphological properties was examined by varying the layer height, infill patterns, and % infill density. Up to 70% roughness reduction was observed as a result of post-FDM ultrasonic application. Additionally, the tensile strength of the samples increased by up to 15.31%. Moreover, for some lower % infill samples, post-ultrasonic tensile strengths were higher than 100% infill control samples. Analysis of scanning electron microscopy (SEM) and X-ray computed tomography (CT) imagery indicated enhanced layer consolidation and reduced void presence in samples treated with ultrasonic. The combination of ultrasonic-generated heat and downward pressure promoted a synergistic squeeze flow and intermolecular diffusion across consecutive layers of polymers. As a result, increased tensile strength and surface finish were achieved while dimensional change was marginal.

In most cases, plant containers used in the horticulture industry are not reusable, have many negative impacts on the environment, and take a long time to degrade. To reduce the use of non-biodegradable plant containers, many bio-degradable plant containers have been developed for the horticulture industry. However, the full potential of the sustainability of plant containers is yet to be completely explored. Therefore, two novel biodegradable plant containers are developed in this research to effectively contribute to sustainability’s environmental, social, and economic dimensions. The two biocomposite formulations are developed by mixing soy hull and soy protein isolate (SPI) with polylactic acid (PLA) matrix for plant containers. In the first formulation, the proportion of PLA and soy hulls are 70 wt% and 30 wt%, respectively; in the second formulation, 65 wt% PLA is blended with 30 wt% soy hulls and 5 wt% SPI. The injection molding process is used to manufacture the plant containers from the two formulations. In a field trial, four plant species are grown in the novel plant containers along with polyethylene and commercial PLA/DDGS (dried distiller’s grains with solubles and PLA-based container) containers to investigate biodegradability and plant growth. The results show that the containers from the new formulations outperform existing biodegradable PLA/DDGS containers in terms of certain plant growth and biodegradability.

This article reviews a novel method to produce microembossed features with an aspect ratio of three and negligible flash on polymer surfaces. An embossing technique that utilizes localized heating (ultrasonic energy) was used with polystyrene and polypropylene substrates. It was demonstrated that when foamed substrates were used, the amount of flash produced was negligible compared to nonfoamed substrates, which has been a significant unresolved problem with embossing using localized heating. The depth of microembossed features as a function of heating times and amplitudes of ultrasonic embossing is detailed in this article, along with a characterization of complex embossed geometries. It was seen that embossing depth was generally proportional to heating time and amplitude until the maximum feature depth was achieved. Although this article deals with embossing of microfeatures for lab‐on‐a‐CD applications, it is envisioned that it is also suitable for lab‐on‐a‐chip applications. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Thermoplastic resins (linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), and polypropylene (PP)) reinforced by different content ratios of raw agave fibers were prepared and characterized in terms of their mechanical, thermal, and chemical properties as well as their morphology. The morphological properties of agave fibers and films were characterized by scanning electron microscopy and the variations in chemical interactions between the filler and matrix materials were studied using Fourier-transform infrared spectroscopy. No significant chemical interaction between the filler and matrix was observed. Melting point and crystallinity of the composites were evaluated for the effect of agave fiber on thermal properties of the composites, and modulus and yield strength parameters were inspected for mechanical analysis. While addition of natural fillers did not affect the overall thermal properties of the composite materials, elastic modulus and yielding stress exhibited direct correlation to the filler content and increased as the fiber content was increased. The highest elastic moduli were achieved with 20 wt % agave fiber for all the three composites. The values were increased by 319.3%, 69.2%, and 57.2%, for LLDPE, HDPE, and PP, respectively. The optimum yield stresses were achieved with 20 wt % fiber for LLDPE increasing by 84.2% and with 30 wt % for both HDPE and PP, increasing by 52% and 12.3% respectively.

This article reviews the application of a coupled squeeze flow and intermolecular diffusion model, which was used to predict the quality and size of microwelds in plastics. Weld widths predictions were compared with previously presented experimental results using moving heat source models and temperature fields. The motivation for this work was to develop and verify a model based on fundamental principles that could accurately predict weld size and strength for conventional plastic welding techniques as well as novel techniques such as laser microwelding. It is envisioned that the resulting model could be used to predict proper welding parameters, including laser power and travel speed, to produce welds of varying size. Although insight into weld quality can be derived from this model, it was not the goal of this work to accurately predict weld strength for laser microwelding because of the difficulty in measuring weld strength on the micron scale. However, as reported in Part 1, weld strength for impulse welds were accurately predicted. In this model it was found that variable temperature histories, rather than a single value of maximum weld temperature, allows more accurate modeling of the welding process. In this work (Part 2), microwelds as small as 11 μm in width were produced with transmission infrared welding. In addition, welds over 150‐μm wide were also generated and the model was able to predict the range of weld widths that were found experimentally. It was found that the predictions were in very good agreement with the experimental results. There was some deviation between the experimental data and the model at the extreme parameters and it is believed that this was due to the temperature‐dependent material properties as well as optical aberrations. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers