Given the long-term use of carbon fibre reinforced polymers (CFRP) in harsh environments, this study investigates the isolated and combined effects of temperature and moisture variations on mode I fatigue delamination propagation. Several levels of temperature and relative humidity were applied as preconditioning and as in-service during fatigue testing to evaluate their effects on the Paris curve. In addition, statistical analyses, including analysis of variance (ANOVA), semi-empirical interpolation modelling, and fractographic assessments, were conducted to provide a comprehensive understanding of the failure mechanisms. The results indicate that the moisture absorbed during hygrothermal preconditioning and the in-service temperature applied during fatigue test individually affect the Paris curve slope. These factors interact synergistically, significantly altering the fatigue crack growth rate. An empirical model capturing this interaction showed good agreement with experimental data, enabling reliable prediction of environmental degradation trends. Fractographic evidence supported the observed changes in fracture patterns, linking changes in fibre bridging formation, surface roughness, and energy dissipation to the observed shifts in fatigue behaviour.

This study explores the adsorption of methylene blue (MB) from wastewater using pinecone residue, a low-cost and abundant biosorbent. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and particle size distribution were used to characterize the material. Particle size strongly influenced both the removal efficiency and the equilibrium capacity. The adsorption performance was optimized using response surface methodology and decision tree regression. Optimal conditions included a contact time > 45 min, an initial dye concentration > 37.5 mg L⁻¹, and a biosorbent dosage of 40–75 mg. Under these conditions, the equilibrium adsorption performance showed a significant improvement over previous studies. Kinetic modeling revealed that the Elovich model best represented the adsorption process, whereas the equilibrium data were most accurately described by the Langmuir isotherm, yielding a maximum monolayer adsorption capacity of 148.54 mg g⁻¹. Additionally, thermodynamic parameters confirmed the spontaneous, exothermic nature of the adsorption, although regeneration studies demonstrated the material's reusability, with increased adsorptive capacity after acid desorption cycles. The findings demonstrate the strong adsorption potential of pinecone residue, emphasizing its efficiency and sustainability for wastewater treatment applications.

Hybrid laminates combining carbon and glass fibres offer an attractive balance of mechanical performance and cost, particularly in sectors such as automotive and wind energy. However, incorporating multiple fibre types gives rise to complex interfacial behaviours that must be thoroughly understood before these materials can be used in structural applications. This study investigates the mode I delamination behaviour of unidirectional carbon fibre laminate (CFL) composite, glass fibre laminate (GFL) composite and hybrid carbon–glass (HCG) fibre-reinforced laminates. To isolate the contribution of fibre bridging, a fracture model based on the Sørensen approach was employed to quantify the bridging zone by fitting energy release rates and opening displacements. Despite their intermediate stiffness, the hybrid laminates exhibited the greatest resistance to crack propagation. This enhanced performance is attributed to the synergistic effect between the rigid carbon fibres and the more flexible glass fibres, which increases both the bridging stress and the end-opening of the bridging zone. The results emphasise the importance of fibre bridging as a primary toughening mechanism in hybrid systems and demonstrate that hybridisation can be employed strategically to enhance delamination resistance.

Hybrid CFRP/GFRP laminates offer an attractive balance between mechanical performance, damage tolerance, and cost efficiency. However, fiber bridging during mode I delamination increases crack-growth resistance while masking the intrinsic fatigue behavior of the material. This study applies a traction–separation-based superposition approach to quantify and isolate the contribution of fiber bridging in unidirectional hybrid laminates under mode I fatigue delamination. The methodology separates monotonic (during pre-cracking) and cyclic bridging contributions using bridging traction curves and fatigue crack-growth data, enabling reconstruction of the zero-bridging Paris curve. Hybrid laminates exhibited enhanced fracture toughness and fatigue resistance, while maintaining intermediate bridging traction behavior compared to nonhybrid systems. After removing bridging effects, hybrid laminates still showed superior intrinsic fatigue performance, indicating that hybridization contributes through mechanisms beyond extrinsic toughening alone. The proposed methodology provides an experimentally efficient framework for fatigue characterization of advanced composite laminates affected by fiber bridging.

Certification of composite structures remains a significant challenge in the aerospace sector. These materials exhibit various failure mechanisms under load, complicating the prediction of crack growth. Delamination is the most common and critical failure, typically triggered by combined tensile and in-plane shear loadings corresponding to Mode I and Mode II, respectively. Characterisation of Mode II remains particularly difficult due to the unstable crack propagation exhibited in many test configurations. This manuscript presents an experimental study of Mode II fatigue delamination at various R-ratios using the End-Loaded Split specimens, which enable stable in-plane shear-driven delamination. A multi-method approach utilising Digital Image Correlation (DIC), Acoustic Emissions, and post-mortem fractography analysis was adopted to provide a comprehensive description of how delamination behaves across varying R-ratios. The study was centred on the fracture process zone, measured via DIC, due to its significant impact on energy dissipation. Variations in the length of this zone throughout the fatigue life revealed an imbalance between the damage mechanisms affecting the growth of the true crack length and the effective crack length. This evolution of the fracture process zone was correlated with trends in acoustic energy dissipation and the morphology of the fracture surface. These findings provide new insights into Mode II fatigue delamination and enhance our understanding for the design of damage-tolerant structures.

The aim of this research is to evaluate the physical, chemical, thermal, and mechanical properties of Itauba (Mezilaurus itauba) wood fiber and Itauba wooden board. The chemical composition presented 33, 29, and 10% lignin, cellulose, and hemicellulose, respectively. The thermal stability was found to be 250 °C for both atmospheres (air and nitrogen), and the simulated TG curve was similar to the one performed on a nitrogen atmosphere. Cone calorimetric results showed a higher steady state when compared to other wood fibers found in the literature with peak heat release rates of 281.762, 424.029, and 482.335 kW/m²when exposed to constant levels of radiant heat flux of 25, 50, and 75 kW/m²at similar weights and densities. Furthermore, X-ray diffraction (13.5% crystallinity) and mechanical tests (flexural and tensile Young’s modulus of 12010 and 969.9 MPa, respectively) were performed on the Itauba wooden board. The tensile results showed to be higher than propylene composites reinforced with 40% wood fiber found in the literature while the storage modulus obtained in the dynamic mechanical thermal analysis found to be higher (11.5 GPa at −130 °C) than most of the commercial thermoplastics used in the industry (polypropylene (9 × 10²MPa), high-density polyethylene (2 × 10³MPa), and polyvinyl chloride (3000 MPa)). This study showed the potential in using Itauba wooden boards in replacing many commercial products, mainly when an adequate mechanical performance is required.

This research investigated the combination of acid functionalization and metal deposition on commercial activated carbon (AC) for the synthesis of electrodes for applications in supercapacitors. The effect of acid treatment and the deposition of metals, including nickel, copper, and cobalt on the electrochemical characteristics of the carbon material were assessed. The AC treatment with sulfuric acid resulted in a nearly twofold increase in surface area compared to the untreated AC, enhancing porosity and creating irregularities that improved the motion of ions and electrons, increasing the specific capacitance and energy density. Notably, we demonstrate that nickel deposition at only 2 wt% significantly improved specific capacitance (up to 59.58 F·g⁻¹), while preserving porosity and enhancing surface wettability. The adoption of a scalable, solvent-free, and low-energy technique for metal deposition on carbon structures presents promising opportunities for developing sustainable alternatives in energy storage technologies.

Polymer composites used in structural applications are subjected to dynamic loads that can generate fatigue-induced microcracks. As these microcracks grow and merge, they lead to material failure, thereby reducing the service life of the component. To address this challenge, a promising strategy involves the development of smart self-healing polymers that, similar to biological systems, respond to damage by activating self-repair mechanisms, effectively enhancing the durability and lifespan of the material. This study investigates the interlaminar shear behavior of 5HS carbon fiber/epoxy composites containing varying amounts of the self-healing agent EMAA, processed via RTM. It examines the influence of agent content on mechanical performance and confirms, through thermal analysis, the feasibility of laminate fabrication, though particle dispersion may limit agent volume. ANOVA results show that EMAA content has a higher effect on mechanical response than internal dispersion. Weibull analysis indicates a linear decrease in shear strength with increased EMAA due to reduced stiffness from its ductile nature. Healing was most effective in interlaminar regions, achieving up to 62% recovery in shear strength, 106% in toughness, and 57% crack area reduction. Predictive modeling supports optimizing healing agent levels to meet design needs while reducing experimental effort and cost.

The design of damage-tolerant aeronautical composite structures often involves thin-walled components that are susceptible to in-plane mixed-mode fracture. Unlike with metals, this process is complicated by the composites anisotropy and the lack of standardized procedures for predicting failure in notched, holed or cracked composites under mixed-mode loading. This study introduces a novel Modified Arcan Fixture (MAF) for testing Compact Tension Shear (CTS) specimens of carbon fibre woven reinforced polymer composite. Digital Image Correlation (DIC) was used to capture strain fields and calculate Stress Intensity Factors (SIFs), which were then compared to analytical predictions for different mode combinations and notch lengths. R-curves were generated for specimens exhibiting self-similar crack propagation. The results revealed that failure modes were dominated by tensile cracking in Mode I and compressive cracking in Mode II, indicating that a single-parameter fracture criterion inadequate for the failure description. A theoretical model that incorporates both tensile and compressive cracking is proposed, which can accurately predict the complete mixed-mode fracture envelope. Furthermore, Scanning Electron Microscopy (SEM) and X-ray micro-tomography were used to elucidate the mechanisms of surface failure and the morphology of internal damage.

Laminate composites are increasingly being used in the transport sector due to their lightweight structures, resulting in fuel savings. However, waste is generated in the form of post-industrial or post-consumer goods that end up in landfill or incineration. One way to minimize the impact of these disposals is through recycling or reuse, but introducing reused fibers with reduced length has been a challenge to keep the mechanical properties. In this context, this research aims to evaluate the influence of the fabric (satin weave) length on the tensile properties of discontinuous laminate and investigate the failure process of such composites manufactured with carbon fabric waste generated at the cutting process. For this purpose, two types of laminates were manufactured, each comprised of five plies (i) three continuous plies and two discontinuous plies; and (ii) one continuous ply and four discontinuous plies with varied fiber length. The laminates were tested by tensile loading, and the strain field was monitored by a non-contact technique called digital image correlation (DIC), which allowed the investigation of the local strain variation due to the interrupted section. It was possible to observe a sharp stress range in which the joint failure was evidenced by strain field variation over the joint. For both laminates, it was possible to depict the events that constrain the tensile strength of the discontinuous laminates, which is severe in laminates with surface discontinuity, and it shows to be advantageous to employ a continuous ply on both surfaces, improving loading transfer between plies. Highlights: Environmental problem related to carbon fiber waste from the cutting process. Take advantage of using small pieces of carbon fiber fabric in laminate architecture. Investigation of the influence of fabric disposition and fabric length on in-plane mechanical properties. Analysis of failure events using strain field measurements via DIC.

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.

Impact damage to composite structures results in multiple, complex failure modes, often requiring the replacement of entire components and thereby escalating aircraft maintenance costs. To address this issue, the present study investigates the damage propagation behaviour with particular emphasis on intra- and interlaminar failure modes. Carbon fibre/epoxy composites were subjected to tensile after impact (TAI) fatigue tests at different energy levels to induce different damage modes and extents within the specimens. A non-destructive testing technique (C-scan) was used to assess the interlaminar damage propagation, while the intralaminar fracture toughness of the post-impact specimens was characterised using a finite fracture mechanics model. The results show that the crack propagation behaviour is strongly influenced by the initial impact damage characteristics, in particular the impact energy level. Lower impact energies tend to promote interlaminar failure modes leading to fatigue crack propagation by delamination. Conversely, higher impact energy levels induce fibre fracture, resulting in a self-similar relationship between intra- and interlaminar propagation.

Discharging oil-contaminated wastewater into the environment without adequate treatment can have a negative impact on water resources, public water and wastewater treatment systems, and even human health. In this sense, it is essential to develop compact, easily automated, low-cost, and highly efficient unitary treatment processes in order to comply with legal requirements regarding effluent emission standards for water bodies. Therefore, the present study consisted of the development of two treatment processes aimed at the separation of oil emulsions stabilised by anionic surfactants: a sorption column using polyurethane/graphene foam composites as sorbent material and a continuous flow AC electroflotation reactor. Initially, composites with 0.5% and 1% w/w graphene (based on polyol mass) were developed using a dispersing agent (1-methyl-2-pyrrolidone). The foams were characterised in terms of morphology and mechanical and sorption properties. In the fixed bed column, the foams retained up to 77.15% of the emulsified oil and 52.36% of the anionic surfactants. In the continuous flow electroflotation reactor, emulsified oil removal efficiencies above 90% were achieved at all electrical currents tested, and up to 88.6% of anionic surfactants were removed at an electrical current of 150 A. Given the advantages and disadvantages of the two oily effluent treatment processes, their combined use in the same system proved promising.