Additive manufacturing (AM) is an advanced technology where parts are fabricated layer-by-layer to create three-dimensional parts in less time. However, challenges exist due to the timeconsuming and material waste in costly testing of the parts for a specific application. In this study, we aim to accelerate the qualification process of AM Inconel 718 parts by establishing the locationbased microstructural changes impact on the mechanical behavior of the part and correlating to the thermal history of the part at those locations. Using Hall-Petch relationships, yield strength at different locations related to the part's microstructural parameters and thermal history. This study reveals effect of location-based microstructure and properties on global performance of the part. Local properties will be extended to create a global stiffness matrix, and boundary conditions will be applied to the part in a model to predict the lifetime of an AM metallic part. Hence, this approach reduces the cost of testing, and the time required to qualify an AM metallic part to an extent across various industries.

As NASA missions extend beyond low Earth orbit, increasing reliance is placed on carbon fiber reinforced polymer (CFRP) composites for spacecraft structures where mass efficiency, durability, and long-term reliability are critical. In service, these materials are subjected to a combination of ultraviolet radiation, vacuum, ionizing radiation, atomic oxygen, and extreme thermal excursions under sustained mechanical loading. Flight systems such as the Boeing Starliner and SpaceX Dragon employ external composite structures that will experience these environments for extended durations. Although prior spaceflight and ground studies have reported limited changes in bulk mechanical properties, the synergistic effects of these environments on composite microstructure, particularly at the fiber matrix interphase, remain insufficiently characterized and represent a potential qualification and reliability risk. This study investigates the effects of short-term cryogenic exposure on a radiation shielding carbon epoxy composite, SC2020, as a ground-based analog for space relevant thermal extremes. The SC2020 material system has previously flown on the International Space Station under the Materials International Space Station Experiment (MISSE) program. Composite specimens were exposed to liquid nitrogen for 6 and 24 hours and evaluated using a multiscale characterization framework that combined ASTM D3039 tensile testing, Atomic Force Microscopy (AFM) based interphase analysis, and helium gas permeability measurements. Tensile testing showed no statistically significant or permanent degradation in global strength or modulus following cryogenic exposure. In contrast, AFM measurements revealed reductions in interphase modulus, weakened adhesion, and increased nanoscale heterogeneity, indicating localized degradation mechanisms not captured by conventional bulk testing. Gas permeability measurements showed a progressive increase in helium diffusion with exposure duration, consistent with micro-void formation or partial interfacial debonding. The results indicate that cryogenic exposure initiates degradation at the fiber matrix interphase while leaving global mechanical properties largely unchanged over short durations. These findings underscore the importance of multiscale diagnostics for identifying early-stage damage mechanisms that may influence long term performance and qualification margins for spaceflight composite structures. The data presented establish a cryogenic baseline for comparison with forthcoming MISSE flight exposure results and support ongoing NASA Established Program to Stimulate Competitive Research (EPSCoR) efforts aimed at improving composite qualification methodologies, risk assessment, and reliability prediction for space environments.

Temperature-modulated differential scanning calorimetry (TMDSC) and Fourier transform infrared (FTIR) spectroscopy were used to study the interphase behavior of polyvinylpyrrolidone (PVP) on reduced graphene oxide (rGO). In this study, in situ prepared rGO was used due to its thermal stability around the glass transition temperature of bulk PVP (176 degrees C). Based on FTIR results, it was found that the PVP molecules cover many of the residual functional groups of the rGO surface and H-bonding occurs. The H-bonding interaction produces tightly bound PVP on the rGO surface. Unfortunately, the thermal signature of the tightly bound segments of PVP on the rGO was weak and not directly quantifiable from the TMDSC thermograms of the composite samples. This was in contrast to the cases for either poly(methyl methacrylate) (PMMA) or poly(vinyl acetate) (PVAc) on silica where the thermal activity (peaks) from the tightly bound polymer were quantifiable. Therefore, a different analysis was conducted to indirectly estimate the amount of tightly bound PVP absorbed on the rGO from the "missing" PVP thermal signal. Linear regression of the data fitted to this model provided an estimate of the amount of tightly bound PVP on the rGO surface as 0.84 +/- 0.03 (SD) mg PVP/m2 rGO. Above this bound amount, the tightly bound fractions decreased with increased adsorbed amounts, as expected. This result was also similar in amount to the previously reported H-bonded systems mentioned above on silica, where the signature of a tightly bound polymer was directly observed, and the tightly bound amount was on the order of 1 mg/m2 (for PMMA, 1.21 and PVAc, 0.78 mg/m2). This work also highlights the need for caution when interpreting the bulk-like intense DSC peaks from thermal analysis as the only indication of the strength of the polymer surface interaction.

This study proposes the use of commercially available graphene nanoplates (GNPs) as a potential filler to optimize the bandgap energy of polyaniline (PANI). In situ cationic polymerization of PANI was performed with various concentrations of GNPs. The morphology, microstructure, and optoelectronic properties of the polyaniline-graphene nanoplates (PANI-GNP) composites were studied using numerous analytical tools. The in situ polymerization of aniline in the composites resulted in the exfoliation of stacked graphene sheets due to the intercalation of the polymer molecules among the graphene sheets and the H-bond interaction among residual functional groups on the graphene surface and the polymer. The thermal stability and electrical conductivity of PANI in the composites increased with increasing GNPs content, as evidenced by the thermogravimetry and DC electrical conductivity analysis. The bandgap energy of pure PANI and the composites was deduced using the Tauc equation. Incorporating GNPs resulted in decreasing the optical bandgap energy of PANI from 3.25 to 2.47, 2.36, and 2.34 eV in the 5%, 10%, and 15% PANI-GNP composites, respectively.

Each year, a significant number of carpets and rugs are landfilled in the United States because their recycling poses difficult challenges. The most commonly recycled plastic is poly(ethylene terephthalate) (PET), which typically comes from plastic bottles, is already easily recycled, and even circularly used to make new bottles. However, the bottle caps, typically made of polyolefins, are often mixed with other materials such as labels, ink, and remnant products, which create challenges for separation and recycling. This research focused on making composites using postconsumer polypropylene carpets (cPP) and mixed polyolefins (rPO) recovered from postconsumer bottle waste by compression molding. The quality of the molded samples was characterized by flexural strength and modulus, creep behavior, and optical microscopic images. The effects of soil contamination and mixing with a polyolefin elastomer on the mechanical properties of the composites were also examined. These samples showed significant mechanical properties suitable for structural applications with strength and modulus values greater than those of most bulk commercial thermoplastics. In addition, we demonstrate that the carpet backing enhances the mechanical properties of the components. So rather than being a "cost" to recycling, the backing can be a benefit.

In the United States, over 90 % of discarded carpets end up in landfills, primarily due to the costly and timeconsuming process of mechanically separating carpet fibers from their backing. This research uses a novel approach for reusing post-consumer polyethylene terephthalate (PET) by developing recycled composites from post-consumer PET carpet (cPET) and recycled PET (rPET) resin sourced from bottle discards via compression molding. Incorporating whole carpets in the process significantly reduces preprocessing costs and time. A design of experiments approach was employed with variables such as temperature, pressure, dwell time, and composition to optimize mechanical properties. A two-level fractional factorial design for screening followed by a three- level full factorial design was performed to identify suitable processing parameters to achieve better mechanical properties. The optimal molding processing conditions for rPET/cPET (30/70) composites were identified as 270 degrees C for 250 s under 1 MPa, which yielded a flexural strength of 54.6 +/- 6.0 MPa and a flexural modulus of 3180 +/- 110 MPa, as verified through reproducibility testing on 10 samples (2 samples each from 5 molding experiments). These enhanced mechanical properties showcase the potential of rPET/cPET composites for structural applications. The composites made up of 30 % recycled PET resin and 70 % post-consumer PET carpet show that a larger fraction of carpet offers a sustainable alternative approach to reduce landfill waste from carpets and develop environmentally friendly materials with good structural integrity.

Every year, billions of pounds of carpets are discarded in landfills in the USA, raising concerns in terms of environmental pollution and economic liability. Approximately 100 billion plastic bags are discarded annually, which are often mixed with other materials (like ink, filler, and remnant products). Due to their heterogeneous nature, only about 3% of the bags are recycled. Processing the discarded materials to form useful composites can add additional value to materials that would otherwise end up in landfills. We have made composites using post-consumer polypropylene carpets (c-PP) and high-density polyethylene (r-HDPE) retail bags recovered from post-consumer sources by compression molding. Molding of the components under different pressures, temperatures, and compositions was performed. Preliminary molding conditions were based on analyzing the differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA) data for different raw materials. Molding factors were examined to define applicable ranges for each parameter. The effects of layup configuration, composition of components, temperature, molding time, and pressure were considered in the screening process. The quality of the molded samples was compared based on flexural strength and modulus, creep behavior, and microscopy. Molded samples showed good mechanical properties with potential for structural applications. The ability to recycle plastic waste will improve sustainability and reduce the environmental impact of plastic use.

Carpets significantly contribute to landfills, forming 3.5 % of the U.S. landfill waste, with less than 10 % being recycled. This study uses intact carpets to create functional composites as a potential solution to this problem. This research introduces a feasible method for manufacturing recycled composites through compression molding of post-consumer polypropylene (PP) carpet and recycled high-density polyethylene (HDPE) resin. Optimal molding temperature and composition ranges were identified using a comprehensive three-level full factorial design of experiments (3D-DOE), resulting in impressive flexural strength (>40 MPa) and flexural modulus (>2000 MPa). Reproducibility tests of 10 specimens yielded 41.8 +/- 2.0 MPa flexural strength and 2200 +/- 150 MPa flexural modulus. These composites, containing up to 70 % potentially-landfilled carpet and 30 % recycled resin, surpassed the performance for the strength of commercialized thermoplastics, making them suitable for structural applications. The findings present a promising approach to address carpet landfilling while reducing reliance on additives.

Delamination is one of the major concerns for carbon fiber reinforced polymer (CFRP) composites. Improving fracture toughness reduces delamination and allows for the creation of multifunctional CFRP. In this study, polyaniline (PANI) coated graphene nanoplatelets (GNP) are introduced in the interlaminar region of CFRP pre-preg with the aid of environmentally friendly thermoplastic polymer, polyvinylpyrrolidone (PVP). The GNP content is varied as 1, 3, and 5% by weight with respect to PVP. The improvements in the fracture toughness are investigated using a double cantilever beam test. An improvement of approximately 79% in mode-I fracture toughness is observed with the addition of 5 wt% GNP with respect to PVP. Dynamic mechanical analysis results confirmed the improvements in storage modulus but showed a decrease in glass transition temperature with the addition of nanofiller. Various spectroscopic analysis and imaging techniques were used to understand and evaluate the interactions of nanocomposites with CFRP pre-preg.

The objective was to manufacture and test hybrid composite sandwich structures for improved thermal and acoustic protection properties compared to state-of-the-art sandwich structures. Hybrid sandwich composite panels consisting of a flexible silica aerogel core, Divinycell foam encapsulated with a Gore membrane layer and E -glass fiber infused with SC -15 epoxy or vinyl ester (VE) face -sheets were manufactured by Vacuum Assisted Resin Transfer Molding (VARTM) process. The porous aerogel core was encapsulated with a Gore membrane layer to allow for the removal of air while preventing resin infiltration during processing. These multifunctional composites combine thermal and acoustic shielding with structural performance. Baseline tests were conducted with the aerogel core encapsulated with glass fiber reinforced SC -15 epoxy facesheets while the final tests were conducted on the sandwich composite that also included the Divinycell foam and infused with VE resin. Steady-state thermal and acoustic measurements were performed in the temperature range of 662 degrees C to 200 degrees C and in the frequency range of 125 Hz to 8000 Hz, respectively. The surface temperature on the cold side of the composite panels was reduced by 62 to 68% to between 35 and 44 degrees C (95 to 112 degrees F) even when the hot -side temperature of the panels reached 149 degrees C (300 degrees F). From acoustic test results, it was shown that the aerogel material provided significant improvements in acoustic damping and reduction in sound transmission. The transmission loss (TL) for the composite panels was between 23 and 51 dB in the frequency range of 125-8000 Hz. These results were accomplished with a composite panel close to 25 mm (1") in thickness. Structural test results indicated that the encapsulation of aerogel blankets within the composite resulted in a reduction of 34% in the moment capacity and 46% in the flexural stiffness. From the results, a sandwich composite panel composed of epoxy face sheets and a combination of Divinycell foam layer, and a silica -based aerogel core represents a lightweight sandwich composite offered significant improvements in thermal insulation and acoustic damping. The encapsulation of the core in the sandwich also protected the core from damage and extended the useful life of the insulation.

Polyaniline and graphene nanoplatelets (PANI-GNP) nanocomposites are synthesized by in situ oxidative polymerization of polyaniline using an oxidizing agent, ammonium peroxy disulphate (APS). The mass of GNP in the nanocomposites varied by 5, 10, and 15 wt polyaniline coated graphene nanoplatelets (PANI-GNP) nanocomposites are chemically characterized and using Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, Scanning electron microscopy (SEM), UV-Vis spectroscopy, and X-ray diffraction analysis (XRD). FTIR and Raman spectroscopy analysis confirmed the uniform coating of polyaniline on GNP. The SEM micrograph and XRD pattern demonstrate the polymerization quality and crystallization degree of samples. UV-Vis analysis showed a decrease in the bandgap of polyaniline, which confirms that nanocomposites are more suitable for optoelectronic application because of variation in the bandgap. TGA analysis showed the thermal stability of PANI is increased with the increased mass of GNP. This study suggests the potential of GNP as a filler for efficient modification in the morphological, electrical, optical, and thermal properties of PANI.

Multifunctional carbon fiber-reinforced polymer (CFRP) composites are promising structural materials for lightweight applications. However, the low conductivity in the through-thickness direction of the composites limits its applications in the fields that require the high stability of composite against lightning strikes. This work presents the study on the synergetic effect of conducting polymer, polyaniline (PANI), and graphene nanoplatelets (GNP) for increasing the electrical conductivity of CFRP composites. PANI doped GNP flexible film is fabricated with the aid of compatible polymer polyvinylpyrrolidone (PVP), and its effect on the electrical conductivity of CFRP composites has been studied. About 250% in through-thickness conductivity has improved with 11 wt% GNP as a function of the composite. The incorporation of conductive film not only increases the conductivity of the CFRP laminates but also enhances the resistance against lightning strikes. Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), three-point bending tests were used to analyze the morphology, thermal stability, and mechanical strengths of the composites. Finally, the observation of post-strike damage confirms the importance of through-thickness conductivity for mitigating the lightning strike damage.

Epoxy resins exhibit good thermal stability, excellent chemical resistance, and enhanced modulus. Despite the favorable properties of epoxy resins, their high crosslink density causes them to be inherently brittle. Recent studies have focused on the potential of carbon-based nanomaterials such as GO to address these issues in epoxies. However, the presence of oxygen within these functional groups could degrade GO thermo-oxidatively and result in the loss of valuable properties of pristine graphene. Past research has reported the successful grafting of GO with suitable molecules like POSS to optimize thermal stability. In this work, a hybrid polymer modifier (HPM) has been developed by grafting Methacryl Polyhedral Oligomeric Silsesquioxanes (MAPOSS) to GO via a redox reaction. HPM was characterized using Fourier Transform Infrared (FTIR), Raman analysis, X-ray diffraction (XRD), X-ray fluorescence (XRF) spectroscopy, Thermogravimetric Analysis (TGA), and Transmission Electron Microscopy (TEM). XRF analysis showed that 10.2 mass% of silicon was added to GO due to the MAPOSS grafting. Furthermore, Raman analysis confirmed the increased structural distortion of GO induced by the incorporation of MAPOSS ((ID/IG) HPM= 1.43, (ID/IG) GO = 1.30). The dispersion of HPM was studied using optical microscopy in Epoxy.

The influence of polyhedral oligomeric silsesquioxanes–polyvinylpyrrolidone on the interlaminar fracture toughness of carbon fiber-reinforced composites (CFRPs) is investigated in this study. Baseline composite material is fabricated using novolac epoxy-infused carbon fiber prepreg. Glycidyl isobutyl polyhedral oligomeric silsesquioxanes (GI) is introduced in the CFRP at loading of 1, 3, 5, and 10 wt.% with respect to polyvinylpyrrolidone used as a compatibilizer. Results of the double cantilever beam test indicate an increase of 70% in interlaminar fracture toughness for 5 wt.% GI-POSS loading compared to the baseline composite. Scanning electron microscopy shows polyhedral oligomeric silsesquioxanes enhanced the adhesion between fiber and the resin that leads to the fiber pull-out. Dynamic mechanical analysis result captures the reduction in the storage modulus with addition of polyvinylpyrrolidone due to the plasticization effect. Nonetheless, the introduction of polyhedral oligomeric silsesquioxanes increases the storage modulus for the GI/PVP composite. Additionally, an increase in the glass transition temperature with the reinforcement of polyhedral oligomeric silsesquioxanes is observed.

The use of thermoplastic micro- and nanocomposites for space-related neutron shielding applications is examined. The materials of particular interest are high in hydrogen content such as polyethylene and polyimide resins, and additives that provide structural support and desirable mechanical properties such as boron nitride, boron carbide, boron nitride nanotubes, and carbon fiber. This chapter covers some of the topics relating to the selection of particular materials which provide benefits that exceed current industry standard aluminum alloys. Results from various studies regarding computational radiation modeling, mechanical testing, thermal stability analysis, and radiation exposure data are provided and analyzed as a whole. The overall analysis shows that composites made from high-density polyethylene and boron nitride provide superior radiation shielding at smaller amounts than required of aluminum and further study into the use of this material with carbon fiber in sandwich composites is of particular interest.

In this work, recycling of post-consumer carpets into structural composites using a modified vacuum assisted resin transfer molding process has been demonstrated. Fabrication of carpet composites addressed the problem related to the environmental effect of waste carpet. Application of the recycled carpet composite as the noise barrier structure has been studied in terms of noise absorption coefficient. Results show that the carpet composite absorbs noise better than conventional noise barrier at a wide spectrum of frequency. Effect of weather exposure on the carpet composite showed the degradation in the mechanical properties. Nanoclay films are also used on the carpet composite and show no change in the noise absorption ability.

Lightweight conductive polymers are considered for lightning strike mitigation in composites by synthesizing intrinsically conductive polymers (ICPs) and by the inclusion of conductive fillers in insulating matrices. Conductive films based on polyaniline (PANI) and graphene have been developed to improve through‐thickness conductivity of polymer composites. The result shows that the conductivity of PANI enhanced by blending polyvinylpyrrolidone (PVP) and PANI in 3:1 ratio. Conductive composite thin films are prepared by dispersing graphene in PANI. The conductivity of composite films was found to increase by 40× at 20 wt% of graphene inclusion compared with PVP and PANI blend. Fourier‐transform‐infrared (FTIR) spectra confirmed in situ polymerization of the polymer blend. The inclusion of graphene also exhibits an increase in Tg by 21°C. Graphene additions also showed an increase in thermal stability by approximately 148°C in the composite films. The mechanical result obtained from DMA shows that inclusion of graphene increases the tensile strength by 48% at 20 wt% of graphene reinforcement. A thin, highly conductive surface that is compatible with a composite resin system can enhance the surface conductivity of composites, improving its lightning strike mitigation capabilities.

More than 250,000 metric tons (600 million pounds) of carpet are dumped in landfills every year. That creates a significant concern regarding environmental deterioration and economic liability. It is therefore imperative to develop sustainable post-consumer carpet-based products for high-value engineering applications such as composite tooling. To be considered as an acceptable composite tooling material, the composite needs to meet certain required properties such as a low coefficient of thermal expansion, excellent compressive properties, and high a hardness value after repeated exposure to curing cycles. The tooling composites must also exhibit the ability to endure several curing cycles, without deteriorating the mechanical properties. In the present investigation, post-consumer carpet has been recycled in the form of structural composites for tooling applications. The recycled carpet composites have been reinforced with 0.5 wt.% of graphene nanoplatelets to modify the material properties of the carpet composites. The results from compressive and hardness experiments demonstrate that the recycled carpet preserved its mechanical integrity even after several curing cycles. This indicates that recycled carpet composites have the potential to be a low-cost composite tooling alternative for the industry.

The present study investigated the influence of different compatibilizer on the dispersion of polyhedral oligomeric silsesquioxane (POSS). The effect of POSS dispersion in the epoxy resin in terms of mechanical, and thermal properties were reported. The three solvent used to disperse POSS in this work are ethanol, acetone, and toluene. The POSS was initially dispersed in the solvent followed by an addition in the epoxy resin by systematically varying the weight fraction from 0.5 to 8 wt%. Mechanical properties of nanocomposites were characterized in terms of elastic modulus, and fracture toughness. The obtained result illustrates that nanocomposites prepared by polar solvent dispersion such as ethanol showed an increase in values of elastic modulus and fracture toughness value.The increase in the modulus and fracture toughness value is due to the better interaction between POSS and ethanol disperse the POSS uniformly in the epoxy resin while avoiding the agglomeration. However, nanocomposites prepared by non polar solvent does not show substantial change in the mechanical properties. Fractured surface morphology was studied using scanning electron microscopy. Differential scanning calorimetry and dynamic mechanical analysis illustrates that with better POSS dispersion value of glass transition temperature (T-g) increased. Fourier transformation infrared spectroscopy showed that POSS completely interacted with the epoxy resin and no phase separation was observed.

Graphene oxide (GO) nanoparticles were introduced in the interlaminar region of carbon fiber–epoxy composites by dispersing it in a thermoplastic polymer carrier such as polyvinylpyrrolidone (PVP). Mode‐I fracture toughness (GIC) was investigated using double cantilever beam testing to evaluate the effect of the GO on the delamination behavior of the composite. The GO content was varied from 0% to 7% by weight as a function of the PVP content. Improvement of ∼100% in the Mode I fracture toughness (GIC) was observed compared to composites with no GO. The optimum amount of nanoparticles for improving the interlaminar fracture toughness was found to be ∼0.007% by weight of the composite. The increase in the value of flexural strength value was also observed. Scanning electron microscopy of fracture surfaces, X‐ray diffraction, and transmission electron microscopy, and reflectance Fourier transform infrared spectra, as well as Raman spectroscopy results, are presented to support the conclusions. POLYM. ENG. SCI., 59:1199–1208 2019. © 2019 Society of Plastics Engineers