Search Results (232)

Due to recent developments across the aerospace, power generation and defense sectors, the demand for flat-surfaced components with extremely high surface quality is rapidly increasing. In this regard, although abrasive machining processes often produce fine, contaminated swarf that is frequently relegated to landfill, these processes remain critical for the engineering sector. Motivated by increasing sustainability and circularity pressures, this narrative review examines the current state of the art in recycling and repurposing the chips, tooling and cutting fluids that are typically generated or consumed within grinding processes. In doing so, a number of methodologies for extracting useful materials from swarf slurries are identified, including pyrometallurgical routes (applied successfully to Ni–Co alloys, for example), hydrometallurgical strategies (e.g., iron leaching from ferrous swarf) and, in the case of non-metallic materials such as CMCs and CFRPs, chemical processing methods. Various means of separating abrasive constituents and removing contaminants from grinding swarf are also highlighted, within which centrifugation and heat treatment are found to be particularly useful for non-ferrous materials such as titanium alloys or composites, whilst ferrous materials are largely magnetically separated. Prospective applications for spent abrasive tooling are also explored, including reuse as shot, waterjet machining feedstock, road surface additives, or mortar in the context of cement production. Likewise, heat- and radiation-based strategies for prolonging cutting-fluid life are highlighted, and their associated sustainability benefits and limitations discussed, despite ultimate disposal still being relegated to fuel usage or landfill. Ultimately, this review identifies the scarcity of grinding-specific recycling process data and highlights the need for robust, publicly accessible recycling strategies for novel material systems. Full article

Carbon fiber-reinforced polymer (CFRP) is favored as the primary material for thin-walled components in fields such as aerospace due to its excellent properties, including light weight, high specific strength, high specific stiffness, and ease of integrated manufacturing. These thin-walled parts require assembly and connection with other components using rivets or bolts, necessitating the drilling of a large number of holes in CFRP. However, owing to its macroscopic heterogeneity, anisotropy, and low interlaminar bonding strength, CFRP is prone to defects during drilling, such as delamination, burrs, tearing, fiber pull-out, and surface voids. These defects can significantly compromise the connection quality and fatigue life of the components and may even lead to part rejection. To avoid drilling defects and achieve high-quality machining of CFRP, it is essential to fundamentally understand the intrinsic relationship between its material characteristics, such as anisotropy and interlaminar properties, and machining-induced damage. This paper systematically reviews the primary defects in CFRP drilling and their formation mechanisms, identifying drilling forces, drilling heat, and tool wear as the core contributing factors. Based on this analysis, various process optimization methods from different perspectives are proposed to mitigate these drilling defects and improve surface quality, including the optimization of cutting parameters, tool improvement, enhancement of the drilling environment, optimization of drilling process strategies, and the application of advanced drilling technologies. Finally, the paper summarizes the research on CFRP drilling and provides an outlook on future developments. Full article

This study investigates ultrasonic wave propagation in carbon fiber reinforced polymer (CFRP) composites containing foreign object debris (FOD) by introducing a novel method to characterize the depth and size of FOD, from a single captured waveform generated by an out-of-focus spherically focused transducer. Current methods of inspection utilize a raster approach to both detect and quantify FOD, which is limited to identifying FOD smaller than 4 mm. The method introduced in the present paper allows for a single point scan to detect and quantify FOD, as small as 0.5 mm, with the highest error in the depth estimation being less than 8%. This paper presents experimental testing to inform a finite element analysis of a full waveform simulation of an immersion tank inspection environment and compares waveforms between testing and simulation. A transient pressure acoustic model is developed in the COMSOL Multiphysics environment to simulate wave propagations. Simulation results provide waveform reflection and transmission at material interfaces, which will occur when there is an acoustic mismatch between materials. The transmitted ultrasonic wave is partially reflected toward the transducer upon encountering material interfaces between the water, CFRP laminate, and the FOD. Simulation results show that the acoustic profile and pressure of the reflected wave captured by the transducer allows an accurate identification of FOD depth and size within the composite structure, suggesting an alternative method of inspection to quantify FOD characteristics faster than through conventional approaches. Results show an increase in captured signal pressure of over 125% between the 0.5 mm FOD and the 1 mm FOD located on the mid-plane of the laminate, and 500% between the same 0.5 mm FOD and 1 mm FOD placed near the front wall. These results suggest the potential sensitivity limits for physical component. This work demonstrates that small FOD, which are often difficult to resolve and quantify under conventional raster-based inspection, can be reliably identified by intentionally positioning the specimen within the defocused region of a spherically focused transducer. Results are presented to correlate the reflected acoustic pressure amplitude to defect depth, transducer–specimen distance, and FOD size, providing an approach to quantitatively discriminate small defects that would otherwise produce ambiguous signals. Full article

This paper presents the design, manufacturing, instrumentation and validation by tests (ground and icing wind tunnel) of a full-scale Hybrid Laminar Flow Control (HLFC) leading-edge demonstrator based on Airbus A330 outer wing plan-form. The Ground-Based Demonstrator (GBD) was developed to reproduce a full-scale, realistic wing section integrating into the leading-edge three key systems: micro-perforated skin for the hybrid laminar flow control suction system (HLFC), the hot-air Wing Ice Protection System (WIPS) and a folding “bull nose” Krueger high-lift device. The demonstrator combines a superplastic-formed and diffusion-bonded (SPF/DB) perforated titanium skin mounted on aluminum ribs jointed with a carbon-fiber-reinforced polymer (CFRP) wing box. Titanium internal ducts were designed to ensure uniform hot-air distribution and structural compatibility with composite components. Manufacturing employed advanced aeronautical processes and precision assembly under INCAS coordination. Ground tests were performed using a dedicated hot-air and vacuum rig delivering up to 200 °C and 1.6 bar, thermocouples and pressure sensors. The results confirmed uniform heating (±2 °C deviation) and stable operation of the WIPS without structural distortion. Relevant tests were performed in the CIRA Icing Wind Tunnel facility, verifying the anti-ice protection system and Krueger device. The successful design, fabrication, testing and validation of this multifunctional leading edge—featuring integrated HLFC, WIPS and Krueger systems—demonstrates the readiness of the concept for subsequent aerodynamic testing. Full article

The truss transfer story serves as a critical structural zone connecting different structural systems in high-rise buildings. This component incorporates numerous inclined-web trusses, which are prone to cracking and failure under seismic events. To enhance the seismic performance of long-span transfer structures and address the tensile cracking vulnerability of inclined-web trusses in conventional truss transfer stories, this study investigates the seismic behavior of a novel composite system: a prestressed CFRP tendon–steel-reinforced concrete transfer story structure with inclined-web trusses and two specimens of inclined-web truss transfer story frames—with and without prestressed CFRP tendons—were designed and fabricated. These specimens were subjected to horizontal low-cycle reversed loading to examine seismic performance indicators, including crack propagation patterns, failure modes, hysteretic curves, skeleton curves, stiffness degradation, ductility, and energy dissipation capacity. The results demonstrate that incorporating prestressed CFRP tendons into the inclined-web trusses did not alter the failure mode of the steel-reinforced concrete transfer story structure. The primary failure morphology consistently manifested as flexural-shear failure in the bottom chord columns. During the loading process, tensile cracking failure manifested in the inclined-web members of both specimens, with and without prestressing. Crack distribution remained uniform in all cases. The inclined-web trusses incorporating prestressed strands exhibited an 80% increase in cracking load compared to the non-prestressed specimen. Furthermore, the prestressed specimen demonstrated superior resistance to performance degradation and enhanced energy dissipation capacity. Both configurations exhibited significant deformation capacity and satisfactory seismic performance. The prestressed CFRP tendons enhance the crack resistance and deformation capacity of a transfer story structure with inclined-web trusses, providing novel insights for seismic design of truss transfer story structures. Full article

This study presents the development, calibration, and validation of cohesive zone models (CZMs) for epoxy-based adhesive joints connecting stainless steel and CFRP composites. The objective of this study is to develop and rigorously validate cohesive zone models for epoxy-based adhesive joints between stainless steel and CFRP composites, ensuring their reliability for numerical simulations of structural failure under quasi-static and large-deformation conditions. The work focuses on accurately describing the quasi-static behaviour and failure mechanisms of hybrid adhesive interfaces, which are crucial for multimaterial structures in modern transportation systems. Experimental tests in Mode I (DCB) and Mode II (ENF) configurations were performed to determine the cohesive parameters of the structural adhesive SikaPower 1277. The obtained data were further analysed through analytical formulations and validated numerically using PAM-CRASH. Excellent agreement was achieved between experiments, analytical predictions, and simulations, confirming the reliability of the proposed material definitions under large deformations. The validated models were subsequently implemented in a large-scale numerical simulation of a bus rollover according to UN/ECE Regulation No. 66, demonstrating their applicability to real structural components. The results show that the developed cohesive zone models enable accurate prediction of failure initiation and propagation in adhesive joints between dissimilar materials. These findings provide a robust foundation for the design of lightweight, crashworthy structures in transportation and open new perspectives for integrating epoxy-based adhesives into additively manufactured hybrid metal–composite systems. Full article

The design of aircraft components is a complex process that must simultaneously account for environmental impact, manufacturability, cost and structural performance to meet modern regulatory requirements and sustainability objectives. When these factors are integrated from the early design stages, the approach transcends traditional eco-design and becomes a genuinely sustainability-oriented design methodology. This study proposes a sustainability-driven design framework for aircraft components and demonstrates its application to a fuselage panel consisting of a curved skin, four frames, seven stringers, and twenty-four clips. The design variables investigated include the material selection, joining methods, and subcomponent thicknesses. The design space is constructed through a combinatorial generation process coupled with compatibility and feasibility constraints. Sustainability criteria are evaluated using a combination of parametric Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) regression models, parametric Finite Element Analysis (FEA), and Random Forest surrogate modeling trained on a stratified set of simulation results. Two methodological pathways are introduced: 1. Cluster-based optimization, involving customized clustering followed by multi-criteria decision-making (MCDM) within each cluster. 2. Global optimization, performed across the full decision matrix using Pareto front analysis and MCDM techniques. A stability analysis of five objective-weighting methods and four normalization techniques is conducted to identify the most robust methodological configuration. The results—based on a full cradle-to-grave assessment that includes the use phase over a 30-year A319 aircraft operational lifetime—show that the thermoplastic CFRP panel joined by welding emerges as the most sustainable design alternative. Full article

Steel plates with open holes are common in engineering structures such as bridges and towers for pipeline penetrations and connections. These openings, however, induce significant stress concentration under alternating tension–compression loading (stress ratio R = −1), drastically accelerating fatigue crack initiation and threatening structural integrity. Effective identification and mitigation of such stress concentrations is crucial for enhancing the fatigue resistance of perforated components. This study proposes a closed-loop methodology integrating theoretical weak zone identification, targeted CFRP reinforcement, and experimental validation to improve the fatigue performance of open-hole steel plates. Analytical solutions for dynamic stresses around the hole were derived using complex function theory and conformal mapping, identifying critical stress concentration angles. Experimental tests compared unreinforced and CFRP-reinforced specimens in terms of circumferential strain distribution, dynamic stress concentration behavior, and fatigue life. Results indicate that Carbon fiber-reinforced polymer (CFRP) reinforcement significantly reduces stress concentration near 90°, smooths polar strain distributions, and slows strain decay. The S–N curves shift upward, indicating extended fatigue life under identical stress amplitude and increased allowable stress at identical life cycles. Comparison with standardized design curves confirms that reinforced specimens meet higher fatigue categories, providing practical design guidance for perforated plates under alternating loads. This work establishes a systematic framework from theoretical prediction to experimental verification, offering a reliable reference for engineering applications. Full article

The search for innovative solutions in the field of construction materials used in aircraft manufacturing has led to the development of composite materials, particularly CFRP polymer composites. Composite airframe components, which are required to have high strength, are joined using mechanical fasteners. Considering that the composite consists of a polymer matrix, which is a material susceptible to rheological phenomena occurring rapidly at elevated temperature, there is a high probability of significant changes in the strength and performance properties. Coupled thermal and mechanical loads on composite material joints occur in everyday aircraft operation. Experimental tests were conducted using a quasi-isotropic CFRP on an epoxy resin matrix with aerospace certification. The assessment of changes in the strength parameters of the material itself showed a decrease of approx. 40% in its short-term strength at 80 °C compared to the ambient temperature and a decrease in the load-bearing capacity of single-lap bolted joints of over 25%. Even more rapid changes were observed when assessing the fatigue life of the joints assessed at ambient and elevated temperature. In addition, the actual glass transition temperature of the resin was determined using the DSC technique. Analysis of the damage mechanisms showed that at 80 °C, the main degradation mechanisms of the material are accelerated creep processes of the CFRP and softening of the matrix, increasing its susceptibility to damage in the joint area. Full article

Multifunctional aerostructures that carry mechanical loadings while conducting electrical currents offer a promising approach to reduce the weight of Electrical Power Systems (EPS) of aircraft. However, Carbon Fibre-Reinforced Polymer (CFRP), when used for aerostructures, presents challenges in achieving multi-functionality due to anisotropic mechanical, electrical, and thermal properties. These properties are interdependent on both laminate-level design factors (fibre/resin choice, fibre volume fraction, stacking sequence, and electrode configuration) and system-level EPS constraints (allowable voltage drop, current, and installation geometry). State-of-the-art material design and selection methods lack a coupled mechanical–electro–thermal design and selection approach to overcome these challenges of a complex design space to enable identification of multifunctional CFRP (MF-CFRP) solutions. This paper presents the first methodology for the design and selection of MF-CFRP with combined electrical, structural, and thermal properties. The methodology integrates requirement capture, laminate layup determination, electro-thermal assessment, option ranking, and manufacturing route selection. The methodology couples laminate-level design factors with system-level EPS constraints and includes iterative loops to refine either the CFRP design or the EPS parameters when no solution initially exists. The methodology is demonstrated to enable the design of a CFRP component to conduct the electrical current as part of the 28 V_DC network in an aircraft. This case study demonstrates the value of the methodology to identify knowledge and dataset gaps necessary for MF-CFRP design, alongside enabling the design of MF-CFRP components to enable increased power density of weight-critical EPS. Although the case study focused on a 28 V_DC system, the methodology is generalisable to other aircraft electrical architectures since system-level electrical parameters are used within the methodology as adaptable inputs. Full article

Carbon-Fiber-Reinforced Plastic (CFRP) is a typical lightweight material used in the aerospace industry. However, the automotive industry has focused on the application of composite materials in vehicle components for weight reduction. In particular, hybrid parts consisting of CFRP reinforcement and a steel outer have been investigated in many studies as a solution to satisfy weight reduction and high strength. In this paper, a steel/CFRP hybrid part was evaluated by impact analysis using several material models, such as the Johnson–Cook model, progressive damage analysis (PDA), and cohesive zone model (CZM). First, the mechanical properties of the steel were determined under different strain rates to assess collision effects. Subsequently, the material properties of the CFRP were evaluated to predict the failure of composite material in the tensile and compressive directions. In addition, the cohesive properties of adhesive film were evaluated under normal and shear modes. Finally, impact analysis using the obtained material properties was conducted to predict the behavior and strength of the steel/CFRP hybrid part under collisions, and the results were compared with the experimental results for verification. Full article

Carbon fiber reinforced polymer (CFRP) components require precise curing process control to ensure quality, but traditional phenomenological cure kinetics models face limitations in handling nonlinearity and data diversity. This study addresses the challenges in modeling the cure kinetics of carbon fiber reinforced polymer (CFRP) composites, where traditional phenomenological models lack generalizability and neural networks suffer from robustness issues due to their numerous hyperparameters and data dependency. To overcome these limitations, a novel machine learning model called the angle information-enhanced radial basis function (RBF) model is proposed, which integrates both Euclidean distance and angular relationships between data points to improve prediction stability and accuracy. The performance of this machine learning approach is systematically compared against an autocatalytic model and a neural network using dynamic DSC data from T700/2626 epoxy resin at multiple heating rates. The angle-enhanced RBF model balances accuracy, efficiency, and robustness, offering a reliable data-driven alternative for CFRP cure kinetics prediction without requiring extensive data or complex hyperparameter optimization, thus facilitating better process control in manufacturing. Full article

This paper proposes a multi-objective optimization method that integrates deep neural networks (DNN) with gray relational analysis (GRA) to optimize lay-up configurations for carbon fiber-reinforced plastic (CFRP) automotive components. Specifically, a lab-scale CFRP B-pillar structure was investigated to simultaneously maximize structural strength and failure safety. A DNN surrogate model was trained using finite element simulations of 2000 random stacking sequences to achieve high predictive accuracy. The trained model was then used to evaluate all possible lay-up combinations to derive Pareto optimal solutions. Gray relational analysis was subsequently employed to select the final optimal configurations based on designer preferences. The selected lay-up designs demonstrated improvements in both strength and failure safety. To validate the proposed framework, laboratory-scale CFRP B-pillar was fabricated using a prepreg compression molding process and subjected to bending tests. The experimental results confirmed an error below 5% and failure trends consistent with the simulation results, thereby validating the reliability of the proposed method. The proposed DNN-GRA approach enables efficient multi-objective optimization with reduced computational effort and flexibility in reflecting different engineering priorities. Full article

This study proposes a hybrid flexural strengthening technique for reinforced concrete (RC) beams by combining the near-surface mounted (NSM) and externally bonded reinforcement (EBR) methods. In this technique, iron-based shape memory alloy (Fe-SMA) strips are used for the NSM component, while either a carbon fiber reinforced polymer (CFRP) sheet or an Fe-SMA sheet is applied as the EBR component. The proposed hybrid-strengthening method aims to enhance the flexural load capacity and ductility of existing RC beams. To evaluate the effectiveness of the proposed method, numerical models were developed using ABAQUS software and validated against experimental results. A comprehensive numerical investigation was carried out on 52 RC beams, categorized into six groups with various hybrid-strengthening configurations. In addition, the effect of the prestressing of NSM Fe-SMA strips and the prestressing of EBR CFRP or EBR Fe-SMA sheet on the flexural performance of the beams was also examined. The results indicated that the hybrid-strengthening method significantly improved the cracking, yielding, and ultimate load capacities of the beams; however, in most cases, it reduced their deflection. Notably, prestressing the EBR Fe-SMA sheet in beams with higher reinforcement ratios produced a pronounced improvement in ductility. Full article

This research study investigates the use of composite materials to reduce the weight of heavy industrial vehicle chassis. A new Carbon Fibre Reinforced Polymer (CFRP) crossmember was developed to replicate the mechanical performance of the traditional steel component while achieving substantial weight reduction. A multi-step approach was adopted: analytical and finite-element analyses were performed on single crossmembers to assess bending and torsional stiffness. The CFRP design achieved increases of 6.8% in torsional stiffness and 5.0% in bending stiffness, with a 68.1% weight reduction. After confirming stiffness equivalence, full chassis simulations were carried out to evaluate global performance. The steel model reproduced experimental results with a relative error of 1.13%, while the CFRP configuration enhanced overall torsional stiffness by 7.8%. Extending these results to all crossmembers, the initial cost increase of the CFRP solution could be recovered within about 2 years for the diesel scenario and 3.5 years for the electric one. Environmental benefits were also quantified, with annual CO₂ reductions of 708.4 kg and 298.6 kg, and cost savings of up to 463.3 EUR/year and 299.8 EUR/year, respectively. Full article