Search Results (43)

A progressive damage model was developed to study the damage and failure behavior of CFRP/Ti double-bolt scarf joints under quasi-static loading. The three-dimensional Hashin failure criterion was integrated into a finite element model via the ABAQUS user-defined material subroutine. Quasi-static tensile tests were conducted to investigate failure mechanisms and validate the model. The predicted failure modes match the experimental results with an error of 11.8% in the prediction of ultimate load. The effect of helicoidal layup on the composite joint was studied for the application of a helicoidal composite. The results show that the helicoidal layup configuration with a 45/−45 layup on the surface had the highest failure load, and the helicoidal layup introduced more tensile damage in the matrix. This study offers practical failure prediction methods and comprehensive failure mode analysis for composite bolted scarf joints. Full article

To address the insufficient bonding performance between TC4 (Ti-6Al-4V) coating and carbon fiber-reinforced thermoplastic (CFRP) matrices that limits engineering applications of composite structures, TC4 coatings were fabricated on CFRP polymer composites via laser cladding and analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to examine the interface morphology, microstructure, and phase composition. The influence of laser processing parameters on the cladding quality was assessed based on the mechanical performance of the TC4 coating. The findings revealed that insufficient laser power (<230 W) or excessive scanning speed (>1.4 m/min) led to incomplete melting of TC4 powder, preventing the formation of intermetallic compound (IMC) layers. Conversely, excessive laser power (>270 W) or a low scanning speed (<1.0 m/min) caused thermal decomposition of the CFRP due to its limited thermal resistance, leading to interfacial defects such as cracks and pores. The interface between the CFRP and TC4 coating primarily comprised granular TiC and acicular α′ martensite, with minor TiS₂ detected. Optimal mechanical performance was achieved at a laser power of 250 W and a scanning speed of 1.2 m/min, yielding a maximum interfacial shear strength of 18.5 MPa. These findings provide critical insights for enhancing the load-bearing capacity of TC4/CFRP aeronautical composites, enabling their reliable operation in extreme aerospace environments. Full article

This study examines the intrinsic optical enhancements of carbon fiber-reinforced polymers (CFRPs) achieved through the integration of magnesium oxide (MgO) nanoparticles, as well as Mg/MgO and titanium dioxide (TiO₂) thin films onto carbon fibers. Integration was performed by quasi-continuous electrophoretic deposition (EPD) and physical vapor deposition (PVD), respectively. Employing a customized electrophoretic cell, EPD facilitated uniform MgO nanoparticle deposition onto unsized carbon fibers, ensuring stable nanoparticle dispersion and precise fiber coating. As a result, the fibers exhibited increased ultraviolet (UV) reflectance, largely attributed to the optical properties of the protective MgO layer. In parallel, PVD enabled the deposition of Mg/MgO and TiO₂ thin films with tailored thicknesses, providing precise control over key optical parameters such as reflectivity and interference effects. Mg/MgO coatings demonstrated high UV reflectivity, while TiO₂ layers, with their varying refractive indices, generated vibrant colors in the visible (Vis) range through thickness-dependent light interference. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) assessed the quality, thickness, and uniformity of these thin films, and UV/Vis spectroscopy confirmed the influence of deposition parameters on the resulting optical performance. Post-lamination analyses revealed that both EPD and PVD modifications significantly enhanced UV reflectivity and allowed for customizable color effects. This dual strategy underscores the potential of combining EPD and PVD to develop advanced CFRPs with superior UV resistance, decorative optical features, and improved environmental stability. Full article

A shape-controllable laser-engraving treatment (LET) and aramid pulp (AP)-reinforced resin pre-coating (RPC) were used on a titanium (Ti) alloy surface to construct micro-/nano-aramid pulp and epoxy (MAPE) coatings for greater bonding strength with carbon fiber-reinforced polymers (CFRPs). The array pits of regular hexagon on the Ti alloy surface were engraved and vertical spaces between the array pits were created to place the AP-reinforced epoxy for stronger mechanical interlocking. The specimen treated with laser engraving (side length of 0.3 mm) and AP-reinforced RPC yielded the greatest bonding strength of 27.1 MPa, 67.4% higher than the base strength. The failure modes of the Ti-CFRPs composites changed from debonding failure at the Ti/epoxy surface to fiber-damaged failure of the laminated CFRPs panels. The shape-controllable LET and simple AP-reinforced RPC were confirmed as the most feasible and effective combined methods for use on titanium alloy surfaces for manufacturing stronger Ti-CFRPs composites, which exhibited the potential for application in other metal–matrix-bonding composite systems. Full article

Carbon fiber-reinforced polymer (CFRP)/titanium alloy (Ti6Al4V) stacks are widely used in the aerospace industry due to their excellent physical properties. The substantial demand for drilling components in the aerospace industry necessitates the implementation of enhanced processing efficiency and drilling quality standards. Six-degrees-of-freedom robots are commonly used in the aerospace industry due to their high production efficiency, high flexibility, and low labor costs. However, due to the weak stiffness, chatter is prone to occur during processing, which has a detrimental impact on the quality of the finished product. As an advanced processing technology, ultrasonic-assisted machining technology can effectively reduce the cutting force and suppress the chatter in the drilling process, so it is widely used in production. In this paper, first, the robot kinematic (dexterity) and stiffness performance is analyzed. Then, the appropriate range of the machining plane and the posture of the robot in the workspace are selected. Finally, the vibration and CFRP entrance damage during the machining process are compared and studied in conventional robotic drilling (CRD) and ultrasonic-assisted robotic drilling (UARD). The experimental results demonstrate that the UARD is an effective method for reducing vibration during the machining process. Compared with the CRD, the CFRP entrance delamination damage in UARD is reduced. Under the appropriate processing parameters, the entrance delamination factor could be reduced by 15%, and the burr height could be reduced by 45%. Obviously, the UARD is a promising process to improve the CFRP entrance delamination damage. Full article

This study aims to evaluate the mechanical behavior, by ways of the FEM, of three femoral stems made of a Ti-6Al-4V titanium alloy with transverse holes in the proximal zone and a stem made of a β-type titanium alloy with a stiffness varying from 65 GPa in the proximal zone to 110 GPa in the distal zone and the CFRP composite material. The purpose of the study was to evaluate the effect of stress shielding on an intact femoral bone. A three-dimensional model of the intact femur was created, and the three prostheses were inserted with perfect stem bone fit. Applying constraint conditions such as fixation in all directions of the distal part of the femur and the application of a static load simulating standing still during a gait cycle allowed the stresses of both the implants and the bone to be compared. Evaluating the stress shielding for the three proposed materials was possible by identifying the seven Gruen zones. We can see from the results obtained that the metal alloys produced observable stress shielding in all the Gruen zones. There was a difference for the β-type alloy which, as a result of its stiffness variation from the proximal to the distal zone, did not show any level of stress shielding in Gruen zones 1 and 2. The CFRP composite, in contrast, showed no stress shielding in all of the Gruen zones and is an excellent material for the fabrication of total hip replacements. Further in vitro and in vivo validation studies are needed to make the modeling more accurate and understand the biological effects of the use of the three materials. Full article

CFRP/Ti stacks composed of carbon fiber-reinforced plastic composites (CFRP) and titanium alloys (Ti) are widely used in aerospace fields. However, in the integrated hole-making process of CFRP/Ti stacks, the machining characteristics of various materials are significantly different, and constant machining parameters cannot simultaneously meet the high-quality machining requirements of two materials. In addition, errors exist between the actual thickness of each material layer and the theoretical value, which causes an impediment to the monitoring of the machining interface and the corresponding adjustment of parameters. An adaptive machining method for the helical milling of CFRP/Ti stacks based on interface identification is proposed in this paper. The machining characteristics of the pneumatic spindle and the interface state in the helical milling of CFRP/Ti stacks are analyzed using self-developed portable helical milling equipment, and a new algorithm for the real-time monitoring of the machining interface position and adaptive adjustment of the machining parameters according to the interface identification result is proposed. Helical milling experiments were carried out, the results show that the proposed method can effectively identify the position of the machining interface with good identification accuracy. Moreover, the proposed parameter-adaptive optimized machining method for CFRP/Ti stacks can significantly improve hole diameter accuracy and machining quality. Full article

The tool structure is an important factor affecting the damage of CFRP/Ti stacks machining. However, the impact of tool structure on the formation process of stacks hole damage cannot be fully revealed through experimental methods alone. In contrast, finite element simulation can effectively overcome the limitations of experiments. In this study, a numerical simulation model is established to investigate the relationship between step drill structure and formation process of CFRP/Ti stacks hole damage. Based on this, the research discusses the effect of step drill structure on the burr height of Ti layer, delamination of CFRP, aperture deviation, defects in hole surface. The results show that when the stacking sequence is CFRP to Ti, the burr height of Ti at hole exit decreases first and then increases with the rising of the ratio of primary drill bit diameter to secondary drill bit diameter (k_d). When k_d is 0.6, the burr height of Ti at hole exit is the lower. As k_d increasing from 0.4 to 1.0, delamination factor of CFRP increases by 2.57%, which are affected little by the step drill structure due to the support of Ti. Besides, the aperture size deviation decreases first then increases with the rising of k_d, and the minimum aperture size deviation is 2.09 μm when k_d is 0.6. In addition, as k_d is 0.6, the hole wall defect is fewer. In conclusion, step drill with k_d of 0.6 is suitable for drilling of CFRP/Ti stacks. Full article

The aeronautical industry constantly strives for efficient technologies to facilitate hole-making in CFRP/Ti6Al4V structural components. The prime challenge in this direction is excessive tool wear because of the different engineering properties of both materials. Nanofluid minimum quantity lubrication (NF-MQL) is the latest technology to provide synergistic improvement in tool tribological properties and lubrication function during machining. In the current study, an MoS₂-based NF-MQL system was applied during helical milling using a FIREX-coated tool. In-depth analysis of wear, a scanning electron microscope (SEM), and electron deposition spectroscopy (EDS) were used to evaluate workpiece elemental transfer and tool wear mechanisms. Experimental findings showed that 1% nanoparticles concentration in lubricant resulted in low tool wear of 13 µm after 10 holes. The SEM and EDS analyses depicted formation of tribo-film on the surface, resulting less severe wear and a reduced degree of adhesion. However, a low nanoparticle concentration of 0.5% resulted in 106 µm tool wear after 10 holes with slight evidence of tribo-film. Parametric analysis based on eccentricity, spindle speeds (individual for CFRP and Ti6Al4V), axial pitch, and tangential feed showed correlations with mechanical damage. An extended study of up to 200 holes showed diffusion of C element at a high rate as compared to metal elements such as W and Co. The lowest tool wear was observed using eccentricity level 1, spindle speed Ti6Al4V 1000 rpm, spindle speed CFRP 7500 rpm, tangential feed 0.01 mm/tooth, axial pitch 1.5 mm, and 1% of MoS₂ nanoparticles. Full article

In this study, anodizing treatment was utilized to etch titanium (Ti) substrates’ surface to prefabricate nano-cavities. Resin pre-coating (RPC) and three silane coupling agents’ coating (CAC) techniques were further applied to porous Ti substrates surface to compare the reinforcement effect of adhesive bonding strength. SEM images show that nano-cavities have been prepared to create a greater contact area and vertical volume on Ti substrate surface, fully covered by resin coatings via RPC. A higher surface roughness and better surface wetting are also obtained by the testing results of atomic force microscope and contact angles. Single lap shear tests results indicate that specimens with “anodizing + RPC” treatment yield the best average shear strength of 20.73 MPa, increased by 31.7% compared to anodizing base strength and at least 63.0% higher than silane KH-550/560/792-coated specimens. A dominant cohesive failure and fiber-tearing on CFRP’s shallow surface, instead of adhesive debonding failure, are shown in the appearances of damaged specimens, proving that the RPC technique has a more effective bonding strength reinforcement in titanium and carbon fiber-reinforced polymer (Ti-CFRP) composites’ toughening. Thus, the simple RPC technique can be regarded as a new-type alternative to adhesive joint toughening to manufacture high-performance composites for aerospace applications. Full article

Carbon fiber-reinforced plastic/titanium alloy (CFRP/Ti) stacks are widely used in the aerospace field based on their high strength to weight ratio and heat resistance. High-quality bolt hole assembly is critical for the safety of the aerospace industry. Reaming is a crucial process in precision machining and is extensively used to improve the quality of bolt holes. Due to the different properties of the material, machining with conventional reaming (CR) presents some challenges, such as tolerance variations across the hole group and difficulty in controlling thrust. In this paper, ultrasonic vibration is applied to the reaming process. A geometrical model of ultrasonic vibration reaming (UVR) was established to analyze its kinematic law. UVR experiments on CFRP/Ti stacks were carried out to study the influence of different ultrasonic amplitudes on reaming thrust and the influence of tool speed on thrust, dimensional accuracy, and surface roughness under optimal ultrasonic amplitude. The average thrust forces in UVR decreased by over 57% (Ti) and 40% (CFRP), respectively, compared to CR. The roughness of CFRP is reduced by 20% with UVR and 28% for titanium alloys. The surface topography of the holes is significantly improved by UVR. This work guides the manufacture of high-quality bolt holes for CFRP/Ti stacks. Full article

In this study, a thermomechanical model is developed to simulate a finite drilling set of Carbon Fibre Reinforced Polymers (CFRP)/Titanium (Ti) hybrid structures widely known for their energy saving performance. The model applies different heat fluxes at the trim plane of the two phases of the composite, owing to cutting forces, in order to simulate the temperature evolution at the workpiece during the cutting step. A user-defined subroutine VDFLUX was implemented to address the temperature-coupled displacement approach. A user-material subroutine VUMAT was developed to describe Hashin damage-coupled elasticity model for the CFRP phase while Johnson–Cook damage criteria was considered for describing the behavior of titanium phase. The two subroutines coordinate to evaluate sensitively the heat effects at the CFRP/Ti interface and within the subsurface of the structure at each increment. The proposed model has been first calibrated based on tensile standard tests. The material removal process was then investigated versus cutting conditions. Predictions show discontinuity in temperature field at interface that should further favor damage to localize especially at CFRP phase. The obtained results highlight the significant effects of fibre orientation in dominating cutting temperature and thermal effects over the whole hybrid structure. Full article

Carbon fiber reinforced plastics (CFRP)/titanium alloy (Ti) stacks have been widely used in aviation field due to the superior mechanical properties. During integrated drilling of CFRP/Ti stacks, serious damage occurs in the CFRP layer because of the disparate properties of two stack components. Heat accumulation and thermal induced damage are typical and critical issue during drilling stacks, especially in the interface region. In this study, in order to deeply analyze the thermal influence of the interface region, a numerical model based on the finite difference method is developed to predict the three-dimensional drilling temperature field. Experiments with accurate measurement point are conducted to valid the rational of temperature prediction model. The results confirm that the temperature distributions predicted by numerical study have good agreements with the experimental results and the maximum error is about 10.3%. Furtherly, based on the drilling experiments, it can be found that thermal damage induced by cutting heat occurs as discoloration rings around the hole which could cause the elastic modulus of resin matrix decrease. An empirical model of thermal damage with maximum drilling temperature of the interface region are developed with the correlation of R² = 0.97. The findings point out that as the maximum drilling temperature exceeds 410 °C, serious thermal damage could occur in the resin matrix of CFRP layer. Full article

Materials have a significant role in creating structures that are durable, valuable and possess symmetry engineering properties. Premium quality materials establish an exemplary environment for every situation. Among the composite materials in constructions, carbon fiber reinforced polymer (CFRP) is one of best materials which provides symmetric superior strength and stiffness to reinforced concrete structures. For the structure to be confining, the region jeopardizes seismic loads and axial force, specifically on columns, with limited proportion of ties or stirrups implemented to loftier ductility and brittleness. The failure and buckling of columns with CFRP has been studied by many researchers and is ongoing to determine ways columns can be retrofitted. This article symmetrically integrates two disciplines, specifically materials (CFRP) and computer application (machine learning). Technically, predicting the lateral confinement coefficient (K_s) for reinforced concrete columns in designs plays a vital role. Therefore, machine learning models like genetic programming (GP), minimax probability machine regression (MPMR) and deep neural networks (DNN) were utilized to determine the K_s value of CFRP-wrapped RC columns. In order to compute Ks value, parameters such as column width, length, corner radius, thickness of CFRP, compressive strength of the unconfined concrete and elastic modulus of CFRP act as stimulants. The adopted machine learning models utilized 293 datasets of square and rectangular RC columns for the prediction of K_s. Among the developed models, GP and MPMR provide encouraging performances with higher R values of 0.943 and 0.941; however, the statistical indices proved that the GP model outperforms other models with better precision (R² = 0.89) and less errors (RMSE = 0.056 and NMBE = 0.001). Based on the evaluation of statistical indices, rank analysis was carried out, in which GP model secured more points and ranked top. Full article

The application of adhesively bonded joints in aerospace structural parts has increased significantly in recent years and the general advantages of their use are well-documented. One of the disadvantages of adhesive bonding is the relevant permanence, when compared to traditional mechanical fastening. End-of-life processes generally require the separation of the adherents for repair or recycling, and usually to achieve this, they combine large mechanical forces with a high temperature, thus damaging the adherents, while consuming large amounts of energy. In this work, a novel disassembly technique based on laser-induced shock waves is proposed for the disassembly of multi-material adhesively bonded structures. The laser shock technique can generate high tensile stresses that are able to break a joint, while being localized enough to avoid damaging the involved adherents. The process is applied to specimens made from a 3D-woven CFRP core bonded to a thin Ti layer, which is a common assembly used in state-of-the-art aircraft fan blades. The experimental process has been progressively developed. First, a single-sided shot is applied, while the particle velocity is measured at the back face of the material. This method proves ineffective for damage creation and led to a symmetric laser configuration, so that the tensile stress can be controlled and focused on the bond line. The symmetric approach is proved capable of generating a debonding between the Ti and the CFRP and propagating it by moving the laser spot. Qualitative assessment of the damage that is created during the symmetric experimental process indicates that the laser shock technique can be used as a material separation method. Full article