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.

Abstract Polymeric composite materials reinforced with carbon fibers are widely used in the aeronautical, automotive, energy, and marine industries due to their excellent mechanical properties and low density. However, these materials are susceptible to defects introduced during manufacturing or service life, requiring reliable non-destructive testing (NDT) methods to ensure quality and structural integrity. Despite the widespread application of NDT , the literature lacks a critical and comparative overview of their limitations, and suitability for composites. This review provides an analysis of the main NDT methods for polymeric composites, including ultrasonic, X-ray, thermography, and microcomputed tomography testing. The study highlights the advantages and challenges of each method, discussing their suitability for different defect types. The findings indicate that combining multiple NDT methods enhances defect detection reliability, addressing the limitations of individual methods. This study provides a reference for researchers and engineers, supporting advancements in material inspection and structural health monitoring.

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.

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.

The growing demand for sustainable solutions in advanced composite materials has driven interest in reusing carbon fiber-reinforced thermoplastic (CFRT). This study investigates the rheological, mechanical, thermal, electrical, and electromagnetic properties of polyamide 6 (PA6) composites reinforced with recycled CFRT waste. The composites were prepared by the extrusion process with different ground CFRT contents (10 and 20 wt %). Differential scanning calorimetry (DSC) revealed that the presence of carbon fibers acts as an effective heterogeneous nucleating agent, increasing the crystallization temperature and the degree of crystallinity. Mechanical characterization demonstrated significant improvements, with the elastic modulus and ultimate tensile strength increasing by up to 80% and 69%, respectively, while strain at break was reduced due to the restriction of polymer chain mobility and stress concentration around fiber-matrix interfaces. Impact strength improved by 53% at higher ground CFRT contents, driven by energy dissipation mechanisms such as fiber pull-out and crack deflection. Electromagnetic characterization indicated promising shielding effectiveness (SET), reaching up to 16 dB in the X-band, with absorption-related mechanisms presented. The composites exhibit a desirable combination of mechanical performance and electromagnetic interference (EMI) shielding capabilities. These findings underscore the potential of CFRT-reinforced PA6 composites as sustainable, high-performance materials for applications requiring mechanical and electronic requirements.

Considering the complexity of the mechanic analysis in advanced composite materials, studies in the literature have demonstrated the use of machine learning (ML) methods, aiming to predict the mechanical properties in high-reliability levels. ML models have been also used in medical applications, biological sciences, and data control systems, presenting prospects in analyzing and modeling mechanical/thermal behavior for engineering applications. For this purpose, this chapter aims to conduct a systematic review of ML methods on the mechanical properties of structural composites. The analysis of the ML approach parameters and efficiency are also highlighted. A systematic review was performed using the PRISMA methodology to identify the main discoveries in recent studies. A total of 490 studies were initially identified from 2013 to 2022. Then, each article was selected and described by specific inclusion/exclusion criteria. The main findings were presented and discussed, and the gaps are identified to open up further investigations yet to be understood and exploited.

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 environment has been significantly impacted by the extraction of natural resources and generation of agro-industrial waste. Therefore, the handling and transformation of waste have a high potential to replace petroleum-based packaging with biopackaging. Hemicellulose is an agro-industrial waste that is capable of forming a film/bioplastic with hydrophilic characteristics owing to the hydroxyl groups present in the molecule. Thus, the present study aimed to evaluate the effects of xylan acetylation on film formation by manipulating the main process variables such as catalyst concentration and reaction time. Consequently, the effects of acetylation were evaluated on the generated film (hydrophobicity and mechanical strength) and compared to films of natural xylan, starch, and starch structured with natural xylan. The films formed with acetylated xylan showed high moisture resistance, with an 80.70

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.

Renewable materials of biological origin exhibit attractive properties in relation to traditional plastics, as they can be partially or completely replaced, thereby reducing environmental impacts. Hemicelluloses are a group of polysaccharides that have expanded applications when acetylated. Acetylation can improve the mechanical strength and water vapor barrier properties of xylan-based bioplastics. By partially acetylating xylan in the present study, it was possible to use water as a solvent for the film-forming solution and starch as a second polysaccharide in the formation of bioplastics. Xylan was modified via partial chemical acetylation by varying the reaction time, solvent, and catalyst content. The bioplastics were formed by non-acetylated xylan and acetylated xylan with degrees of substitution (DS) of 0.45 and 0.9, respectively, with starch to form blends using glycerol as a plasticizer. Acetylation with DS 0.45 showed better results in increasing the hydrophilicity of the bioplastic. On the other hand, acetylation influenced the thermal stability of bioplastics, increasing the maximum temperature of the degradation rate from 302 °C to 329 °C and 315 °C, owing to changes in the crystallinity of the polymers. In addition to the modulus of elasticity 2.99 to 290.61 and 274.67 MPa for the non-acetylated bioplastic and the bioplastic with DS of 0.45 and 0.90, respectively. Thus, the films obtained presented suitable physicochemical properties for use in various industrial applications, such as active and intelligent packaging in the food sector.

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Structural adhesives are widely used across industry sectors and, specifically in oil and gas, they appear as an alternative for structural joining instead of welding, to mitigate the risks arising from sparks in an environment with highly flammable products. In this sense, this article aims to evaluate the mechanical behavior of adhesive joints using the Double Cantilever Beam (DCB- to determine the GIC, mode I interlaminar fracture toughness) test before and after exposing these joints to severe environmental conditions, such as high humidity and high temperature. Also, three different surface treatments (manual sanding with abrasive sponge, solvent cleaning, and peel-ply application) of the adherend (carbon fiber/epoxy composite) are examined, as well as two different thicknesses of the adhesive layer (0.5 and 1.0 mm) to verify possible influences on the GIC behavior before and after conditioning. The results show that reducing manual surface treatment processes is a better option, to reduce the factors that cause greater dispersion in G IC values. In particular, cleaning the adherend with just isopropyl alcohol (solvent) before applying the adhesive yielded better G IC results among the tested techniques. Regarding thickness, the findings suggest that a greater thickness of the adhesive layer can lead to an increase in the plastic regions, enhancing the dissipation energy and improving the mode I interlaminar fracture toughness. Hygrothermal conditioning revealed the adverse effects of humidity on the adhesive, resulting in a 20-30 % reduction in GIC. IC . Differential Scanning Calorimetry (DSC) analyses demonstrate that conditioning caused a notable reduction in the glass transition temperature (Tg) g ) of the adhesive.

Prepregs are highly dependent on the resin, its chemical composition, and physical properties. Resin is the perishable part of prepreg materials and usually requires controlled storage, otherwise, its processability and properties may be affected. Oven curing prepregs are recognized to have longer life out of the freezer than those designed to cure in autoclave, and one of them, prepreg 2511, is the focus of this research. Prepreg 2511 has a formal out-time limit of 28 days at clean room environment (23 degrees C/50% relative humidity), and 24 months shelf life, when frozen at -18 degrees C, while common prepreg designed to be cured in autoclave, usually have 15 days of out-time and 12 months of shelf-life. It is known that the real shelf life and out time of epoxy-based materials tends to be longer than suppliers' recommendation. Aiming to assess 2511 performance after those 28 days of exposure to clean room ambient, during and after 24 months in freezer; the material was exposed to this environmental condition for more than 28 days and tested periodically using different methods, including, Differential Scanning Calorimeter, High-Performance Liquid Chromatography tack, among others. In resume, the goal of this research was to identify 2511 longest out life without losing its properties and which of the tests used during these experiments would be more sensitive to capture its aging.

Despite the distinct benefits of plastics, the environmental impacts stemming from their production and accumulation in the environment have become a global concern. Therefore, the development of new technologies that mitigate these impacts is of notable importance. The present study aimed to evaluate the physicochemical properties of starch-xylan-based bioplastic, and to discuss the viability of this material in terms of applications and ecological impacts. Holocellulose, xylan, and alpha-cellulose were extracted from waste biomass and combined with starch for bioplastic production. Solubility in food simulants (3% acetic acid, and 90% ethanol) was performed for xylan and starch-based bioplastics. Bioplastic was evaluated to grow Aspergillus versicollor for xylanase production. The bioplastic was evaluated as a photoprotector with yeast exposed to UVC light-covered by the bioplastic for 2 h. Bioplastic disintegration was evaluated in different soil moistures and the disintegration on the surface of the compost. Liquid washes from soils exposed to bioplastic biodegradation were tested for Lactuca sativa seed germination/inhibition. Water from a local lake was exposed to bioplastic and microbial cell density modification was verified. Images of the surface of the bioplastics were obtained by scanning electron microscopy, and characterized by thermogravimetric and dynamic-mechanical analysis. The xylan addition in bioplastic led to a material with a 40-50% decreased ultraviolet light transmittance. An increase in xylan concentration reduced solubility in lipid food simulant solutions, with no fatty solubilization with 25% of xylan. It suggests potential applications in photoprotective and packaging contexts. The thermal degradation temperature of the pure starch bioplastic was 324 degrees C, and the addition of 10% (287 degrees C), 15% (286 degrees C), and 25% (296 degrees C) xylan (w/w) indicated a reduction in thermal resistance, possibly due to suboptimal interaction between polymer chains. The decrease in crystallinity in the compositions 10/90% (Xc = 20%), 15/85% xylan/starch (Xc = 21%) compared to 25/75% xylan/starch (Xc = 11%) also underscored the complexity of polymer interactions within the bioplastic matrix. Tensile strength of pure starch was 1.21 MPa, while the composition of 15/85% xylan/starch exhibited improved strength 2.99 MPa. Further investigation into the interaction between starch and xylan is warranted. Concerning the disintegration of the 25/75% xylan/starch formulation in the soil, the humidity of the soil matrix played a significant role. The disintegration occurred over 5 days and 16 days in compost (55% humidity) and soil (32.6% humidity), respectively. The results of phytotoxicity ( Lactuca sativa seeds) and changes in the physicochemical and biological profile of water (smell, turbidity, phosphorus and nitrogen levels, pH, and bacterial and phytoplankton density/richness), in response to exposure to bioplastics, highlight the necessity of developing this biologically-based and biodegradable technology in concerns about potential environmental impacts. Furthermore, the present study introduces the approach of bioplastic waste recycling using enzyme production biotechnology. In line with the legitimacy of bioplastics as important materials for addressing the challenges posed by their non-biodegradable synthetic counterparts, the presented results broaden the discourse on the feasibility of this biologically based material, contributing to the development of a sustainable society.