Buckypaper (BP), a free-standing porous film composed of entangled carbon nanotube networks, is a promising material for lightweight and multifunctional electromagnetic interference (EMI) shielding. In this study, the effect of multiwalled carbon nanotube (MWCNT) aspect ratio on the processing, microstructure, electrical properties, and EMI shielding performance of buckypapers was systematically investigated. Two commercial MWCNTs with distinct geometries were used: short MWCNTs (S-MWCNT, aspect ratio ≈ 158) and long MWCNTs (L-MWCNT, aspect ratio ≈ 600). Buckypapers were fabricated by vacuum-assisted filtration with and without electrospun polyacrylonitrile (PAN) sacrificial mats. S-MWCNTs readily formed uniform, flexible, and self-supporting buckypapers without processing aids, whereas L-MWCNTs required sacrificial mats to enable film formation. Morphological and structural analyses (FEG-SEM, XRD, Raman spectroscopy, and N2 adsorption) showed that higher-aspect-ratio MWCNTs promote agglomeration and denser networks, while S-MWCNT buckypapers exhibited higher porosity and surface area (up to 205 m2.g-1). Impedance spectroscopy revealed higher electrical conductivity for S-MWCNT buckypapers prepared without sacrificial mats (≈10-1S.cm-1), whereas residual PAN significantly reduced the conductivity. EMI shielding measurements in the X-band (8.2-12.4 GHz) demonstrated excellent shielding effectiveness for S-MWCNT buckypapers, reaching values up to 36 dB at submillimeter thickness, with reflection as the dominant attenuation mechanism. These results demonstrate that MWCNT aspect ratio is a key parameter governing buckypaper processability and functional performance, offering valuable guidelines for the design of lightweight EMI shielding materials.

In the aerospace field, the use of multifunctional composites has become increasingly important in combining different properties within a single component. This chapter addresses the topic of structural polymer composites reinforced with glass, aramid, and carbon fibers impregnated with epoxy resin, specifically their mechanical properties, their susceptibility to hygroscopic environments, and their behavior when impinged with microwaves (8–12 GHz). It is worth mentioning that, many times, it is required that a component reflect microwaves, such as during landing and takeoff procedures in the process of aircraft identification. On the other hand, it is important that the structural composites be microwave-transparent, such as when applied to aircraft and missile radomes. In any situation, it is required that the composite structure attenuates electromagnetic radiation, thereby making a military aircraft, for example, invisible to a radar. Thus, this chapter addresses multifunctional composites and correlates their mechanical behavior with microwave–laminate interaction in the microwave range.

This study investigates the influence of anodizing parameters on the AA2024 aluminum alloy for joining with a PEI/glass fiber composite using the oxy-fuel welding (OFW) method. AA2024 samples were anodized in a 10% phosphoric acid solution under different voltage (10–30 V) and time (5–25 min) conditions. The hybrid joints were produced by OFW and evaluated by lap shear strength (LSS) tests using a full factorial experimental design. The anodizing condition of 10 V for 20 min exhibited the best mechanical performance, reaching 14 MPa. Electrochemical impedance spectroscopy (EIS), combined with wettability, roughness, optical microscopy, and scanning electron microscopy analyses, showed that anodizing promotes the formation of a porous and protective oxide layer, suitable for anchoring the polymer matrix. EIS results revealed a significant increase in corrosion resistance for anodized samples compared to the control sample, with the electrochemical response dominated by the overall behavior of the anodic film. Equivalent electrical circuit modeling confirmed the effectiveness of the barrier layer formed under optimized conditions. Overall, the results demonstrate the potential of anodizing as an effective surface treatment to enhance metal–composite bonding and improve the performance of hybrid joints produced by the OFW process.

Resistance welding of thermoplastic composites critically depends on the quality of the metal-polymer interface formed between the heating element and the polymer matrix. However, the intrinsic chemical incompatibility between metallic heating elements and high-performance thermoplastics often limits joint strength and fracture resistance. In this study, we investigate the use of plasma-engineered siloxane coatings to tailor the interfacial properties of AISI 304 stainless-steel heating elements and enhance the performance of resistance-welded glass fiber/poly(ether imide) (GF/PEI) joints. Thin films based on hexamethyldisiloxane (HMDSO) were deposited by plasma-enhanced chemical vapor deposition (PECVD), followed by oxygen plasma post-treatment to promote surface functionalization via the formation of polar groups. The modified interfaces were characterized by contact angle measurements, FTIR, XPS, and atomic force microscopy, revealing a transition from hydrophobic to highly polar surfaces driven by the incorporation of oxygen-containing species. Mechanical performance was evaluated by single lap shear strength (LSS) testing combined with detailed fractographic analyses using optical microscopy and scanning electron microscopy. The plasma-engineered interfaces exhibited an increase of approximately 48% in lap shear strength compared to untreated joints, accompanied by a clear transition in fracture mode from interfacial failure to intralaminar and mesh wire rupture mechanisms. These results demonstrate that plasma-deposited siloxane coatings provide an effective strategy to bridge the chemical gap in metal-polymer interactions, offering a versatile route for the design of high-performance welded interfaces in structural composite applications.

Plasma Electrolytic Oxidation (PEO) is an advanced electrochemical treatment for lightweight alloys such as Al, Ti, and Mg. It is an environmentally friendly process that utilizes silicate, aluminate, and phosphate-based electrolytes to produce oxide/ceramic coatings with superior physical and chemical properties compared to conventional techniques. Despite extensive studies on coating morphology and performance, systematic investigations into PEO parameter optimization for reducing energy consumption, a major limitation of the process, remain scarce. To address this gap, a full factorial design (23) was employed to evaluate the influence and determine optimized values of three parameters (treatment time, duty cycle, and electrolyte concentration) that minimize average power consumption. The novelty of this work lies in the quantitative demonstration that statistical modeling can disentangle the relative contributions of process variables to energy demand, offering new insights into PEO mechanisms and paving the way for more cost-efficient and sustainable applications. Average power consumption ranged from 3.68 W to 13.67 W, with lower values linked to shorter treatment times and reduced duty cycles. Analysis of variance (ANOVA) confirmed the model’s statistical robustness, explaining 89.86% of the response variability with a low noise level (0.93%). Treatment time and duty cycle were the only statistically significant factors (p < 0.05), contributing 8.85% and 66.98%, respectively. Beyond technological relevance, these findings provide a scientific framework for understanding parameter interactions in PEO and open promising avenues for future industrial and research applications.

In this work, CeO2 nanoparticles were synthesized via the chemical precipitation method. With this objective, two distinct surface functionalization methodologies were applied: the first one uses anionic surfactant (SDS), and the second one uses hexadecanoic acid (C16H32O2). During the development of this work, nanostructured films were obtained via direct mixing and the solvent evaporation method (in situ and ex situ). This material was characterized via thermogravimetry (TGA), differential scanning calorimetry (DSC), field emission gun scanning electron microscopy (FEG-SEM), infrared absorption spectroscopy (FTIR), Raman spectroscopy and X-ray diffraction (XRD). By XRD, when there is adequate incorporation and dispersion of nanoparticles, the characteristic peaks of the CeO2 crystalline planes are observed in the nanocomposites, and by SEM, their microstructures are evaluated to verify the dispersion. The results obtained showed that the synthesis protocols tested for the intended nanocomposite, with in situ or ex situ functionalization, were satisfactory. According to these results, it was possible to observe the agglomeration of nanoparticles without functionalization and confirm the nanometric scale for CeO2 nanoparticles synthesized without functionalization and with in situ functionalization (SDS), and their diameters were between approximately 10 and 15 nm. Additionally, for the PMMA powder, the Tg was 114 °C, whereas for the nanocomposite films, it averaged 53 °C, suggesting that the solvent acts as a plasticizing agent in the studied samples, thus reducing the Tg value. However, when samples obtained from the ex situ protocol by phase transfer with palmitic acid were analyzed, uncertainties were found regarding the adequate dispersion of CeO2 nanoparticles in PMMA, with in situ functionalization by SDS being the most promising.

Customized superabsorbent hydrogels are of significant interest across several fields of science and engineering due to their practical applications. A conventional classification of hydrogels is based on their composition, in which an ion is attached to the polymeric chain, with commercially available hydrogels typically containing of sodium ions. This composition opens the possibility of developing a less explored type of hydrogel based on potassium, which is strategic due to its role as an essential nutrient for both plant and animal life. This enable more beneficial integration into the environment or interaction with various organisms. These aspects contrast with sodium-based hydrogels, which, although more widely used commercially, may pose environmental and biological concerns, including potential toxicity, degradation of soil structure, and health risks such as hypertension and cardiovascular disorders. This study systematically examines the effects of cellulose nanocrystal (CNC) incorporation on the physicochemical properties of potassium polyacrylate-based polymeric hydrogels. Through controlled variation of CNC loading concentrations, we characterize the structure‐property relationships governing hydrogel performance. These polymeric materials were synthesized in an aqueous medium using a free radical technique and subsequently processed through drying, grinding, molding, lyophilization, and electrospinning, resulting in different forms of hydrogel presentations. The materials were characterized using cyclic swelling and deswelling tests, contact angle measurements, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and optical microscopy. The results demonstrated that CNC content directly tuned key properties: FTIR/EDS confirmed CNC integration, swelling tests revealed adjustable absorption capacity, and SEM showed microstructure control in several presentations (films, electrospun mats, particles). These findings highlight the hydrogel’s customizable functionalities—swelling, and deswelling and contact angle—for requests where eco-compatibility and nutrient synergy are critical, advancing the design of adaptive, sustainable hydrogel systems.

Fast-curing prepregs are increasingly gaining attention for high-throughput composite manufacturing, especially in the automotive industry where cost, cycle time, and scalability are critical. In this work, we investigated the thermal and mechanical behavior of a commercial fast-cure carbon/epoxy prepreg processed via hot compression molding in a 13-min cycle. Thermogravimetric analysis (TGA) showed thermal stability up to 300 degrees C, while differential scanning calorimetry (DSC) revealed an atypical dual-mechanism curing behavior. Both dynamic and isothermal DSC analyses demonstrated deviations from conventional kinetics, including non-linear Arrhenius behavior and a shift in activation parameters depending on the method employed. The prepreg achieved a glass transition temperature of 153 degrees C and delivered tensile, compressive, and interlaminar shear strengths of 786 MPa, 276 MPa, and 42 MPa, respectively. With a low void content (2.8 vol%) and full cure completion experimentally confirmed within 13 min, this material demonstrates strong potential for structural automotive applications. The study provides new insights into the kinetic complexity of snap-cure epoxy systems and supports their applicability in fast-cycle composite manufacturing.

Three-phase composites, especially those composed of high performance thermoplastics, have not been properly investigated with respect to their interlaminar fracture toughness. Therefore, this study investigates effect on the interlaminar fracture toughness by adding carbon nanotube buckypaper (BP), tested under cyclic loading in mode I and II. BP weakened the interlaminar fracture toughness in mode I, creating an easy path for crack growth and reducing the strain energy release (SERR) values in the Paris curves. Conversely, under mode II BPs presented no significant influence to the interlaminar fracture toughness and fatigue life; however, a slight improvement was observed due to the bridging effect. The energy balance principle model for opening delamination showed that BP composites require less energy per unit of area to crack growth, resulting in a smoother fracture surface with fewer failure mechanisms. In contrast, BP slightly increased the energy per unit of area for crack growth, leading to a rougher fracture surface with a higher prevalence of failure mechanisms under mode II. This work underscores the importance of examining the individual effects of mode I and II loadings on BP laminates since these interleaves affect the interlaminar toughness and fatigue life differently.

Carbon fiber-reinforced thermoplastic composites are widely used in the aeronautical industry due to their high mechanical properties and low specific weight. Within the select group of thermoplastic matrices, poly (aryl ether ketone) (PAEK) stands out as a semicrystalline material with high glass transition and melting temperatures. This work aims to evaluate how buckypaper (BP) influences the mechanical properties of the composite PAEK/CF. For this, three types of BPs were made using vacuum filtration. The first one is with carbon nanotubes (CNT), the second is with graphene (GR), and the third is a mix of CNT and GR. The influence of BPs in mechanical behavior was performed by an interlaminar short beam test (ILSS), a compression shear test (CST), and an impulse excitation of vibration. Finally, the presence of BP reduced the mechanical properties of the material due to the low adhesion between matrix and BP. In the ILSS test, it was noted a reduction in interlaminar shear of 16% for CNT BP, 20% for GR BP and 28% for hybrid BP. In the CST, a reduction of 32% for CNT BP, 39% for GR BP and 13% for hybrid BP was observed. On the other hand, the composite with hybrid BP presents a greater increase in Young's Modulus, representing a gain of 13%.Highlights The vacuum filtration process used to produce BPs was determined. Morphology evaluation of BPs through scanning electron microscopy. Influence of BPs on the mechanical properties of composites. Effect of nanoparticles on the adhesion between matrix and BPs.

First-principles calculations based on the density functional theory (DFT) represent a sophisticated technique to investigate the mechanical strength of materials in general, although underexplored in polymeric structures such as high-performance thermoplastic polymers. In this study, DFT calculations were systematically conducted to evaluate the effects of strain on the structure of polyether ether ketone, determining the maximum elasticity modulus in a perfect alignment condition of the polymer chain. The atom positions and arrangement of the polymer chains were set based on total energy and force minimizations. The four lowest energy structures were stretched up to 10 Å per monomer, and the results have shown a mean elasticity modulus of 5.93±0.74 GPa, which we attribute to the upper limit for aligned and stretched polymeric chains.

This work aims the processing of multifunctional thermoset composites, consisting of carbon fibers/epoxy resin prepreg, and polybutadiene (BR) mats produced via electrospinning process aiming to provide a composite material with high tenacity. Initially, polybutadiene mats were produced by electrospinning. These mats and prepregs materials were hot compressed at eight different configurations to produce the composites. The quality of the manufactured composites was evaluated by acid digestion, dynamic mechanical analysis (DMA), acoustic ultrasound inspection, impulse excitation, and impact resistance tests. The composites with six layers of electrospun BR showed higher storage modulus value (DMA test), and no significant change was observed in its energy absorption values of impact resistance test. However, it was possible to verify that the presence of the BR mats in the composites hindered the propagation of damage in the material.

Hybrid buckypapers (BPs) composed of graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) hold great potential for applications in flexible electronics, electromagnetic shielding, and energy storage. In this study, hybrid BPs were fabricated and characterized to evaluate their structural, thermal, and electrical properties. Hybrid BPs with varying GNP/CNT mass ratios (0/100, 25/75, 50/50, 75/25, 85/15, 90/10, and 95/5 wt%) were prepared via vacuum-assisted filtration of well-dispersed aqueous suspensions stabilized by surfactants. The resulting hybrid GNP/CNT BPs were dried and subjected to post-treatment processes to enhance structural integrity and electrical performance. Characterization techniques included scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Raman spectroscopy, thermogravimetric analysis (TGA), nitrogen adsorption/desorption isotherms, and impedance spectroscopy (IS). The hybrid GNP/CNT BPs exhibited electrical conductivities comparable to conventional CNT-based BPs. At GNP concentrations of 25 to 50 wt%, electrical conductivity values approached those of CNT-based BPs, while at GNP concentrations between 75 and 90 wt%, a slight increase in conductivity was observed (171%). These results highlight a synergistic effect at lower CNT concentrations, where the combination of CNTs and GNPs enhances conductivity. The findings suggest that optimal conductivity is achieved through a balanced incorporation of both materials, offering promising prospects for advanced BP applications.

This study investigated the influence of an oxide coating generated by Plasma Electrolytic Oxidation (PEO) on the adhesion between AA2024 aluminum alloy and a glass fiber-reinforced polyetherimide (PEI) composite using ultrasonic welding. After welding, the joints were subjected to lap shear testing (ASTM D1002:19) to evaluate mechanical strength, and the fracture surfaces were analyzed for failure mode (ASTM D5573:19) and by scanning electron microscopy (SEM). Samples without PEO treatment exhibited an average shear strength of 5.4 MPa, with failure predominantly by adhesive fracture (ADH), where little to no thermoplastic matrix remained adhered to the aluminum. In some regions, thin-layer cohesive fracture (TLC) was observed, indicating interface failure with a thin residual polymer layer. On the other hand, PEO-treated samples showed a shear strength of 4.2 MPa and failure characterized by fiber rupture and interlaminar fracture of the composite, with fibers strongly bonded to the polymer matrix after testing. This suggests that the PEO treatment promoted a more robust interfacial adhesion, shifting the failure point to the interior of the composite. Although the shear strength was slightly lower in the treated samples, the change in failure mode indicates improved interface integrity, highlighting the potential of PEO for applications requiring efficient joining of dissimilar materials.

The use of wood-based panels such as Oriented Strand Board has grown in civil construction. This follows the contemporary trend towards low environmental impact materials. However, there is a lack of relevant information about their life cycle assessment, appearing as a current and relevant research topic. Experimental panels made with Eucalyptus wood and castor oil-based polyurethane adhesive already demonstrated great physical-mechanical performance. Therefore, this study aimed to continue the evaluation of this innovative product, estimating their potential environmental impacts using life cycle assessment from a cradle-to-gate perspective and comparing the results with traditional panels and literature data. System boundaries, environmental impacts and environmental hotspots were identified using the ReCiPe H method in terms of ten impact categories. Comparing experimental (heat-treated) and traditional panels, the experimental versions performed better in most categories and showed safer behavior in categories related to human health in addition to not using paraffin, termiticide, and other organic chemicals presented in the traditional panels. Though made of different types of adhesives, the adhesive was the main environmental hotspot for both types.

One of the technological challenges in manufacturing components in polymeric composite materials reinforced with carbon fibers is the occurrence of delamination during the drilling process of the parts. Drilling of composite material is a widely used process in the energy, aviation, and automobilist industries since most pieces are assembled by riveting or screwing, and delamination is the factor with the most significant rejection in terms of hole quality, accounting for 60

The current market's imperative demand necessitates the research and development of advanced polymer composites, especially those incorporating nanofillers. Carbon nanotubes, in particular, have attracted significant attention within research and development for their potential in creating multifunctional composites. This study aims to evaluate the impact of incorporating carbon nanotube buckypapers (BP) on the thermal and electrical properties of poly (aryl ether ketone) (PAEK)/glass fiber (GF) composites. The BP was prepared through vacuum filtration and integrated into PAEK/GF composites with varying stacking sequences, followed by hot compression processing. The degradation behavior of the laminates was investigated using thermogravimetric analysis (TGA). The viscoelastic properties, evaluated by dynamic mechanical analysis (DMA), suggested an increase in stiffness with the inclusion of BP in two of the analyzed stacking sequences. Thermal conductivity, measured via the pulse laser method, showed results comparable to the base laminate (0.153 W/m·K). Meanwhile, electrical conductivity, assessed using the four‐point probe method in the in‐plane direction, revealed semiconductor properties, achieving a mean value of 3.162 S/cm for one of the samples, indicating electrical anisotropy within the multifunctional composite material.

Studies on dissimilar materials joining have greatly increased, transitioning from temporary to permanent joining methods. The latter approach is more applicable due to the hybrid structure offering the best properties of the constituent materials, along with the development of new materials and manufacturing procedures. In this study, the AA2024-T3 alloy was treated with plasma electrolytic oxidation (PEO) and a thermoplastic composite/AA2024-T3 hybrid joint was manufactured using oxy-fuel welding (OFW). Morphological aspects, chemical compositions electrochemical and mechanical properties of hybrid composite joints were determined. The results indicated that the joint exhibits a uniform structure. The adhesion between the dissimilar materials reached a strength of 4.2 to 5.2 MPa, with cohesive bonding and without severe degradation of the thermoplastic matrix in some cases. It was observed that PEO treatment decreased the interface shear strength due to the high silicon content presence in the coating. The coatings effectively increased nobility and corrosion resistance, with corrosion rates ranging from 0.0087 to 0.018 mm/year.

The Plasma Electrolytic Oxidation (PEO) process was investigated to enhance the adhesion of AA2024-O aluminum alloy with a polyetherimide (PEI) matrix composite, using oxy-fuel welding (OFW). A Central Composite Design (CCD) statistical model was used to optimize three independent parameters in PEO: immersion time (s), duty cycle (%), and electrolyte concentration (Na2B4O7·10H2O), aiming to achieve a maximum value of shear strength of the hybrid joint (in MPa). The hybrid joint without PEO treatment presented a resistance of 2.2 MPa while the best condition presented a resistance of 9.5 MPa, resulting in a value 4× higher than the untreated material, due to the characteristics of the coating, which presented a more hydrophilic surface, allowing better mechanical interlocking with the polymer matrix and resulting in mixed-mode failure (adhesive, cohesive, and light fiber). In addition to improving adhesion, the PEO treatment provided better corrosion resistance to the alloy, forming an inert aluminum oxide (Al2O3) coating, with an improvement of approximately 99.84% compared to the untreated alloy. The statistical design covers about 77.15% of the total variability of the PEO + welding process, with independent factors influencing around 48.4% of the variability.

In the present study, an anodizing process was applied to aluminum alloy (AA2024-T3) to enhance interlocking in dissimilar joints with glass fiber-reinforced polyetherimide (GF/PEI) composite, using ytterbium-doped laser fiber welding as a heat source. A factorial Central Composite Design (CCD) was conducted to determine the most appropriate processing and optimization parameters, with lap shear strength (LSS) as the response variable. The obtained and fractured joints were characterized. Anodizing effectively improved the interlocking between dissimilar joints, resulting in LSS values of around 16 MPa. Surface impressions were observed in joints with lower shear values, likely due to the ineffective heat distribution in the processed joint. In the AA2024-T3 alloy, the annealing process occurred, beginning with the segregation of the alloy elements at the grain boundaries and subsequently reducing its hardness. The SEM analysis of the laminate in the best welding condition revealed a well-established fracture surface, with cusps, fibers covered by the polymer matrix, and river marks, indicating good consolidation of the process applied to the metal/polymer junction, which is consistent with the highest shear values obtained. These findings have important implications for future research and industrial applications and can help advance the understanding of these materials and processes.