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Vaidya, Uday

Publications and source records attributed to Vaidya, Uday.

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Bioinspired design toward nanocellulose-based materials

Nature provides lots of inspiration for material and structural design for various applications. Deriving design principles from the investigation of nature can provide a rich source of inspiration for the development of multifunctional materials. The bioinspired design templates mainly include mussels, nacre, and various plant species. As a sustainable and renewable feedstock, nanocellulose can be used to fabricate advanced materials with multifunctional properties through bioinspired designs. However, challenges and opportunities remain for realizing the full potential in the design of novel materials. Here, this article reviewed recent development in the bioinspired nanocellulose based materials and their application. This article summarizes the functions (e.g., surface wetting) and applications (e.g., composite) of bioinspired nanocellulose-based materials. The bioinspired design templates are discussed along with strategies, advantages, and challenges to the development of synthetic mimics. Additionally, mechanisms and processes (e.g., chemical modification, self-assembly) leading to biomimetic design are discussed. Finally, future research directions and opportunities of bioinspired nanocellulose-based materials are highlighted.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Recycled Glass Polypropylene Composites from Transportation Manufacturing Waste

In recent years there has been growing interest in developing recycling technologies for composites manufacturing scrap, process waste and end-of-life parts. The focus of this work was to establish processing routes and mechanical property bounds for glass-polypropylene (PP-GF) scrap from the production of parts for truck trailers, automobiles, and rail cars. This study considered PP-GF scrap and demonstrated extrusion-compression molding (ECM) as a viable route for the closed-loop manufacture of composite parts. The results were promising in terms of the strength and modulus retention of the PP-GF recyclate. The tensile strength and modulus was the highest for 50% and 66% recycled content, compared with 100% and 83% recycle content. The flexural strength and modulus of the 100% and 83% recycled compositions was higher than the 66% and 50% recycled content, respectively. The impact energy absorption of the PP-GF recyclate at at all fiber loadings was superior in absorbing energy compared with the incumbent (benchmark) plywood. This work is useful to designers seeking to incorporate recycled materials in their products.

Vaidya, Uday↗
DOE OSTI2023

Enhanced through-thickness electrical conductivity and lightning strike damage response of interleaved vertically aligned short carbon fiber composites

Through-thickness electrical conductivity of carbon fiber reinforced polymers (CFRPs) is a key characteristic that determines the severity of lighting strike-induced damage. Carbon Fibers (CFs) are inherently electrically conductive and therefore provide high conductivity in the direction of the fiber orientation. However, electrical conductivities through the thickness and orthogonal to the CF orientation in CFRPs are governed by the insulating polymer matrix present between CFs. Here, in this work, through the thickness alignment of short CFs in between layers of CFRP laminates is demonstrated to improve the through-thickness electrical conductivity. Composites with interleaved vertically aligned short CF fibers (<150 μm) will be referred as V-fiber composites hereafter. The effect of the V-fiber on the lightning strike damage is evaluated against an artificial lightning strike of 100 kA (modified waveform A of SAE ARP-5412B standard). The improved through-thickness electrical conductivity of CFRP laminates (1.15 S/cm) through vertical alignment of short CFs was compared to reference CFRP laminates (0.13 S/cm) and was found to dissipate the artificial lightning strike current more efficiently. The surface damage after the artificial lightning strike in the V-fiber composites was reduced to 12.69 cm 2 compared to the reference CFRP surface damage of 57.67 cm 2 , a 78% reduction. It was also demonstrated that Joule heat generated due to lightning strike on the composites was significantly less than the reference sample using infrared (IR) thermography. A high retention (up to 78%) of flexural properties (modulus and strength) was observed in V-fiber composites post lightning strike impact as compared to only 47% retention in the reference panel.

42 ENGINEERING↗
DOE OSTI2022

3D printing of a recycled copolyester of terephthalic acid, cyclohexanedimethanol and tetramethylcyclobutanediol

2,2,4,4-Tetramethyl-1,3-cyclobutanediol (TMCD) is a diol monomer for terephthalic acid (TPA) class of copolyesters that can increase the glass transition temperature and mechanical strength in comparison to conventional TPA polyesters. TMCD-modified poly (1,4-cyclohexylenedimethylene terephthalate) (PCTT) has been used to manufacture consumer products with good toughness, heat resistance and clarity. However, the suitability of PCTT in 3D printing had not been evaluated. Therefore, consumer plasticware was used as the starting material to investigate the suitability of this copolyester for fused deposition modeling (FDM). Here, chemical structure, mechanical properties, thermal behavior and viscoelastic properties of this copolyester were studied. NMR spectroscopy found that the copolyester had cyclohexanedimethanol (CHDM) and TMCD contents at 76.5 mol% and 20 mol% of total diol, respectively. 280 °C printing temperature and 110 °C bed temperature were suitable conditions for printing. T g of PCTT was 103 °C (25 °C higher than PETG). Young's modulus and impact strength of printed PCTT were at least 100% and 65% higher than printed PETG, respectively. The ease of printing, superior mechanical properties and T g (103 °C) make the PCTT random copolyester highly applicable in additive manufacturing.

36 MATERIALS SCIENCE↗
DOE OSTI2022

High Pressure and Two-Sided Mold Surface Solutions (CRADA Final Report)

This project provided surface solutions for highly loaded precision tooling relevant to the automotive industry. Previous development work in coatings for Big Area Additive Manufacturing (BAAM) has produced commercialized coatings for low temperature Acrylonitrile Butadiene Styrene (ABS) tools (TD Coat RT) as well as a soft coating for high temperature applications (TD Seal HT). The team developed these coatings and commercialized them during a prior Manufacturing Demonstration Facility (MDF) technical collaboration (NFE-15-05793). During the prior collaboration, commercialization testing was successfully performed by the Boeing and NAVAIR and resulted in an Awards for Composites Excellence (ACE), award at CAMX – The Composites and Advanced Materials Expo 2016. While this work was clearly successful, gaps in the technology were identified, that prevent widespread adoption of large-scale additive manufacturing in high pressure tooling applications prevalent in the automotive industry. In this project we focused on development of surface solutions for two-sided, compression molding tooling printed on a large-scale polymer AM system in an arbitrary build orientation. We have printed a single cavity extrusion compression molding mold using Polyphenylene sulfide/carbon fiber (PPS/CF) materials, 50% by weight CF samples. These processes are commonly used by Original Equipment Manufacturers (OEM) and Tier 1 suppliers for high volume automotive applications. Several OEMs have identified the need for such technology, indicating significant time and monetary savings could be possible if commercially available surface solutions for high pressure Additive Manufacturing (AM) tooling existed.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Impact of biomass ash content on biocomposite properties

Owing to its low cost and sustainable nature, lignocellulosic biomass has been utilized for reinforcing polymers, but it is crucial to understand the impact of high-ash concentrations in biomass on composite strength and processing. Biomass is not only desirable for biofuel production but could also have a strong market, if high-ash biomass is acceptable, for biocomposites. In this work, natural fibers (switchgrass and corn stover) were used to reinforce polylactic acid (PLA) to produce biocomposites. Natural fibers were pretreated to obtain fibers that contain different percentages of ash. The mechanical properties (such as Young's modulus, tensile strength, failure strain, storage modulus) of corn stover/PLA composites remained largely unaffected by the ash concentration of the biomass fibers, despite the large range of ash contents (2.2–11.9 wt%). Furthermore, the tensile strengths of switchgrass/PLA composites were slightly negatively affected by the ash concentration of the switchgrass fibers (0.7–2.1 wt%). Both the switchgrass/PLA and the corn stover/PLA composites exhibited a high-enough tensile strength (49–57 MPa) and suitable complex viscosity (2.0–7.0 kPa·s at the frequency of 3.2 rad/s). They are expected to be 3D-printable through an extrusion-based additive manufacturing process.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Effects of Mechanical Recycling on Carbon Fiber-Based Hybrid Composites

Carbon fiber (CF) reinforced composites are high-performing, highly utilized material systems historically used in aerospace. As the cost of CF decreases, other industries, such as automotive and energy generation, seek to adopt CF composites into their applications. A sudden increase in CF demand may create supply chain issues if the adoption happens without scaling up of the CF production. A solution for reducing the reliance on CF is to substitute some portion of the CF content with another fiber type without significantly reducing the material properties. When multiple reinforcing fillers are introduced into a composite system, the materials system is often referred to as a hybrid composite and in this case a CF-based hybrid composite. To further relieve reliance on CF and with sustainable manufacturing becoming more prominent in industry, mechanical recycling can be employed to replace all or a percentage of the virgin material content. Utilizing recycled content in place of virgin content will further aid in reducing the reliance on virgin CF and decrease overall material costs. Here, the effects of utilizing mechanically recycled feedstocks on the mechanical properties of injection molded samples are explored to understand the feasibility of re-manufacturing recycled CF-based hybrid composites. By determining the mechanical properties and mechanisms in which the properties change through varying recycled content, the assessment of how the material will perform in other manufacturing processes can be inferred. As a result, industry will gain better insight into utilizing mechanically recycled feedstocks to reduce their reliance on the CF supply chain.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Discontinuous Aligned Carbon Fiber Intermediates for Automotive and Related Applications

This work focused on preferentially aligning discontinuous carbon fibers in wet-laid or air-laid processes. It is well known that aligned fibers provides higher directional strength and stiffness. Discontinuous fibers further allow higher degree of draw and formability as the gaps in the fibers allow for higher material movement. The current processes are limited in their ability to align carbon fibers during processing. The aligned fibers have several benefits - (a) in applications where chopped fibers can replace continuous fibers for targeted strength and stiffness metrics, but at a substantially reduced cost; (b) they can tolerate deeper draws than continuous fiber composites in thermo-stamping and compression molding processes; (c) they can be tailored for pultrusion and unidirectional applications. Although pultrusion is primarily a process that adopts continuous fibers, stitch bonded entangled discontinuous fibers can provide unique intermediates. This is analogous to natural coir fibers which get aligned and entangled to produce ropes/rods for example, (d) they can be processed in cross-ply and multi-directional formats, like composite laminates. In this work Neenah Paper partnered with IACMI, UT and ORNL to evaluate structure-process-property relationships with Zoltek carbon fiber. A few process parameters such as machine speed, weight basis, fiber length, effect of fiber sizing, direction of mat lay-up etc. were investigated. The produced mats were converted to thermoplastic composite laminates using polyamide 6 (PA6, nylon) resin. The specific objective of this project is to produce a wet-laid nonwoven carbon fiber mat with a high degree of unidirectional fiber alignment, using discontinuous carbon fibers. The report provides details about the processing, characterization, and lower-upper bound properties.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Layer Time Control for Large Scale Additive Manufacturing Using High Performance Computing

This work proposes to optimize an additive manufacturing AM process to reduce energy and printing cost. The polymer AM process is inherently dependent on the time-temperature history of each layer to maintain geometric tolerances and mechanical integrity. Our preliminary study shows that regression-based layer time control model using thermal images could result in up to 30% build time reduction for simple geometries. This proposed work would use high-performance computing (HPC) to couple the data-driven model with thermal simulation for better predicting layer temperature profiles, improving throughput of large-scale additive manufacturing, and reducing its energy cost. We have developed a method to optimize a layer deposition time (a.k.a. layer time) for large-scale AM via physics-based simulations. A long layer time leads to an over-cooled surface on which a new layer is deposited, and therefore, it may result in a weak bonding or debonding between layers, cracking, or warping. A short layer time leads to a high temperature of the structure due to insufficient cooling, and therefore, the structure may not be stiff enough and may collapse during manufacturing. Therefore, it is important to estimate the optimal layer time in additive manufacturing for a high-quality product. The temperature of a top layer right before deposition is recommended to be slightly higher than the glass temperature of the material. A temperature cooling was approximated to an exponential function of time, and the optimized layer time was obtained based on a target temperature while maintaining a minimal printing time. The material used is carbon fiber-reinforced polycarbonate (CF/PC), and the large-scale deposition system used is LSAM TM from Thermwood Corporation. Three different layer time cases were used for experiments, and a series of thermal images were obtained via an infra-red (IR) camera during the entire AM processes. AM process simulations were performed using a finite element method and the temperature profiles from the simulation were in good agreements with those from experiments. The layer time optimization was performed based on the temperature profiles from the simulations. A layer temperature with the optimal layer time was confirmed as the target temperature through simulation. In addition to the development of a layer time optimization method, we have developed a numerical framework for AM simulation with element activations in sync with toolpath, based on an open source finite element framework, DEAL.II. A major portion of this work was presented at SAMPE 2022 Conference and Exhibition on May 2022, and published in Proceedings of SAMPE 2022.

42 ENGINEERING↗
DOE OSTI2022

Multi-process tooling for discontinuous carbon and hybrid glass fiber thermoplastics

Expensive tooling often constraints the use of composites in the design and development of automotive parts. While there is significant confidence and knowledge in sheet and bulk metals, composite processes are less understood in mass production environment. The processes used to produce composites and resulting properties are influenced by fiber length attrition, resin to fiber ratio, process waste etc. Tool designs are determined very early in the engineering process. It is cost prohibitive to build additional tools, in the event it becomes obvious a better processing method and material would be beneficial, the original decision is not easily changed. In the present work we recognize the bottleneck of tooling costs and provide an approach of multi-process tooling. The innovation of this work is the design and demonstration of a single tool for different processes namely injection, injection-compression and extrusion-compression. The materials used in this study were long and short fiber thermoplastics (LFTs and SFTs). The resulting structure-property relationships have been reported for the materials and processing methods with a battery tray (BT) tool.

Vaidya, Uday↗
DOE OSTI2022

Mechanical Response and Processability of Wet-Laid Recycled Carbon Fiber PE, PA66 and PET Thermoplastic Composites

The interest in recycled carbon fiber (rCF) is growing rapidly and the supply chain for these materials is gradually being established. However, the processing routes, material intermediates and properties of rCF composites are less understood for designers to adopt them into practice. This paper provides a practical pathway for rCFs in conjunction with low cost and, for the most part, commodity thermoplastic resins, namely polyethylene (PE), polyamide 66 (PA66) and polyethylene terephthalate (PET). Industrially relevant wet-laid (WL) process routes have been adopted to produce mats using two variants of WL mats, namely (a) high speed wet-laid inclined wire to produce broad good ‘roll’ forms and (b) 3DEPTM process patented by Materials Innovation Technologies (MIT)-recycled carbon fiber (RCF), now Carbon Conversions, which involves mixing fibers and water and depositing the fibers on a water-immersed mold. These are referred to as ‘sheet’ forms. The produced mats were evaluated for their processing into composites as ‘fully consolidated mats’ and ‘non-consolidated’ as-produced mats. Comprehensive mechanical data in terms of tensile strength, tensile modulus and impact toughness for rCF C/PE, C/PA66 and C/PET are presented. The work is of high value to sustainable composite designers and modelers.

compression molding↗
DOE OSTI2022

Photoinitiator Selection and Concentration in Photopolymer Formulations towards Large-Format Additive Manufacturing

Photopolymers are an attractive option for large-format additive manufacturing (LFAM), because they can be formulated from structural thermosets and cure rapidly in ambient conditions under low-energy ultraviolet light-emitting diode (UV LED) lamps. Photopolymer cure is strongly influenced by the depth penetration of UV light, which can be limited in the 2–4 mm layer thicknesses typical of LFAM. Photoinitiator (PI) systems that exhibit photobleaching have proven useful in thick-section cure applications, because they generate a photoinitiation wavefront, but this effect is time-dependent. This study investigates the light transmission and through-thickness cure behavior in (meth)acrylate photopolymer formulations with the photobleaching initiator bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (BAPO). Utilizing an optical model developed by Kenning et al., lower concentrations (0.1 wt% to 0.5 wt%) of BAPO were predicted to yield rapid onset of photoinitiation. In situ cure measurements under continuous UV LED irradiation of 380 mW/cm2 showed that a 0.1 wt% concentration of BAPO achieved peak polymerization rate within 2.5 s at a 3-mm depth. With only 1 s of irradiation at 1.7 W/cm2 intensity, the 0.1 wt% BAPO formulation also achieved the highest level of cure of the formulas tested. For an irradiation dose of 5.5 J/cm2 at a duration of 3.7 s, cured polymer specimens achieved a flexural strength of 108 MPa and a flexural modulus of 3.1 GPa. This study demonstrates the utility of optical modeling as a potential screening tool for new photopolymer formulations, primarily in identifying an upper limit to PI concentration for the desired cure depth. The results also show that photobleaching provides only a limited benefit for LFAM applications with short (1.0 s to 3.7 s) UV irradiation times and indicate that excess PI concentration can inhibit light transmission even under extended irradiation times up to 60 s.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Applying Acoustic Emission to Large Format Additive Manufacturing

Large format additive manufacturing (AM) is being adapted as a method of producing large structures in a short lead time and cost-effective way. With the growing advancement in AM techniques and application, machine monitoring and part qualification is highly needed. There has been leading research focused on the manufacturing development and feedstock material but minimum research on the structural health monitoring (SHM), defect detection, and nondestructive evaluation (NDE) for large format AM. Scanning large structure using conventional nondestructive testing (NDT) techniques, such as ultrasound or X-ray, and searching for potential defects can be very time consuming, challenging and cost prohibitive. Acoustic emission (AE) is a passive technique that can be used to monitor and locate defect progression in large structures by distributing group of sensors around the part. This research outlines the necessary procedure for implementing AE to AM as a reliability method. The topics this research will display are: (a) Wave propagation/velocity evaluation, (b) an AE attenuation characterization for the anisotropic printed structure and material, (c) background noise measurements of the extruder and gantry system, and (d) assist in optimal sensor selection and placement for monitoring large AM structures with demonstration. This work establishes the foundation for scaling up the SHM-AE system for the large additive platform.

Spencer, Ryan↗
DOE OSTI2022

Anisotropic thermal behavior of extrusion-based large scale additively manufactured carbon-fiber reinforced thermoplastic structures

Large format additive manufacturing (AM) enables rapid manufacturing of large parts and structures with minimum waste in material and energy. Extrusion-based AM deposition processes provide parts with highly anisotropic thermal properties, which are not typically reflected in textbook values for these materials. In order to develop accurate models that describe the directionally dependent thermal behavior of these materials in processing and service, accurate measurements of specific heat capacity and thermal conductivity are required. Here, this work characterizes, documents, and analyzes the effect of the anisotropic nature of the extrusion-based deposition process on the specific heat capacity and thermal conductivity of the resulting AM products. All measurements were made over a temperature range of 20–180°C using the transient plane source technique, also referred to as the hot disk technique. Three of the most commonly used large format AM feedstock materials that utilize carbon fiber reinforcement were examined in this work: acrylonitrile butadiene styrene, polyphenylene sulfide and polyphenylsulfone. Finally, these findings can serve as a thermal design/process guideline for future large format AM applications.

36 MATERIALS SCIENCE↗
DOE OSTI2022

THE DESIGN OF LAYER TIME OPTIMIZATION IN LARGE SCALE ADDITIVE MANUFACTURING WITH FIBER REINFORCED POLYMER COMPOSITES

In this study, we have developed a method to optimize a layer deposition time (a.k.a. layer time) for large-scale additive manufacturing (AM) via physics-based simulations. A long layer time leads to an over-cooled surface on which a new layer is deposited, and therefore, it may result in a weak bonding or debonding between layers, cracking, or warping. A short layer time leads to a high temperature of the structure due to insufficient cooling, and therefore, the structure may not be stiff enough and may collapse during manufacturing. Therefore, it is important to estimate the optimal layer time in additive manufacturing for a high-quality product. The temperature of a top layer right before deposition is recommended to be slightly higher than the glass temperature of the material. A temperature cooling was approximated to an exponential function of time, and the optimized layer time was obtained based on a target temperature while maintaining a minimal printing time. The material used is carbon fiber-reinforced polycarbonate (CF/PC), and the large-scale deposition system used is LSAM TM from Thermwood Corporation. Three different layer time cases were used for experiments, and a series of thermal images were obtained via an infra-red (IR) camera during the entire AM processes. AM process simulations were performed using a finite element method and the temperature profiles from the simulation were in good agreement with those from experiments. The layer time optimization was performed based on the temperature profiles from the simulations. A layer temperature with the optimal layer time was confirmed as the target temperature through simulation.

Jo, Eonyeon↗