Understanding different factors affecting Supersonic Particle Deposition (SPD) repaired Al 7075-T651 plate for structural restoration

One of the main challenges in maintaining aging aircraft is to find a reliable, effective and economic repair process, for both non-structural and structural repairs. Supersonic particle technology (SPD) aka Cold Spray (CS) has proved to be an effective geometry restoration technology and has the potential to repair/restore/enhance the airworthiness of aging aircraft. Al 7075-T651 is highly susceptible for stress crossing cracking compared to –T7351 temper. Mechanism involved in environment assisted cracking (EAC) such as corrosion fatigue primarily in conventional product forms such as rolled plate, extrudate or forging in Al 7075 is complex. Fundamental research concerning the driving force and micro-mechanism involved in EAC is still not matured, and, not completely understood in Al alloys. In addition, the effect of different factors such as high strain rate deformed layers, residual stress in the coating and substrate and presence of micro defects makes more complex in understanding the EAC in SPD repair subjects. In light of the complex nature of the SPD structure, systematic evaluation was carried out to determine various factors affecting the EAC behavior of the SPD repair. Thus, this presentation focuses on a brief overview on the application of this technology for corrosion repair followed by experimental study and fractographic analysis of SPD repaired Al 7075-T651 0.25” plate aimed at restoring the structural functionality. To study the structural behavior of the SPD coated 7075 Al, both static and fatigue performance were evaluated in ambient and humid environment. The study involves simulating a 20% thickness loss by milling Al 7075 master plates (9.1” x 8.75”) followed by depositing Al 7075 spray atomized powder using SPD process. Test coupons were extracted from this master plate; orientation and location of the individual test specimen origin were tracked. The presentation includes factors affecting the quality of the SPD coating specifically for structural application and how to exploit these factors in qualifying a SPD coating. Test results are validated and supported by detailed fractographic studies. Emphasis will be given to failure modes and mechanism involved on these SPD coated specimens tested under cyclic loads, and, under ambient and humid environments will be discussed

Hybrid HfC‐SiCN matrix for improved oxidation resistance of carbon fiber–reinforced mini‐composites

Abstract Hafnium carbide (HfC) is an ultrahigh‐temperature ceramic with high melting point, chemical stability, hardness, and wear resistance. However, its low fracture toughness and poor thermal shock resistance limit its structural applications in extreme environments. In this study, co‐curing of liquid precursors was carried out prior to complete pyrolysis of individual polymeric precursors. First, HfC preceramic polymer precursor was cured, followed by silicon carbonitride (SiCN) precursor curing on a 2D carbon fiber (CF) cloth using the drop‐coating process. The infiltrated CFs were pyrolyzed at 800°C to achieve CF/HfC‐SiCN ceramic mini‐composites. The cross‐linked precursor‐to‐ceramic yield was observed to be as high as 65% when the procedure was carried out in an inert environment. Although stable up to 1200°C, CF/HfC‐SiCN samples demonstrated susceptibility to oxidation at 1500°C in ambient air. The oxidation of HfC in the presence of SiC leads to the formation of a hafnium‐containing silicate (HfxSiyOz) along with hafnia (HfO2). This compound of silicate and hafnia limits oxygen diffusion better than SiO2 and HfO2 individually. The incorporation of SiCN in HfC ceramic led to improved phase stability compared to a neat HfC system. The results of this study also show that the use of liquid‐phase precursors for HfC and SiCN in the polymer‐infiltrated pyrolysis method is a promising approach to fabricating high‐temperature structural ceramic matrix composites with good oxidation resistance

Influence of machining process of MoS2/B4C/Az31 Mg alloy composite and its tribological characteristics

The automotive, biomedical, and aerospace industries are among those with a rising need for lightweight materials with enhanced mechanical and tribological qualities. Composites based on magnesium alloys have attracted interest because of their excellent strength-to-weight ratio and promise to improve component performance. Magnesium (Mg) alloy-based composites find applications in sports and leisure equipment, aerospace, biomedical implants, and more. The research outlined here serves a critical need in the field of materials science and engineering, particularly regarding the development of advanced magnesium (Mg) alloy-based composites. In this study, we have created a new aluminum composite using the AZ31 alloy mixed with 5% boron carbide (B4C) and 5% molybdenum disulfide (MoS2) as reinforcement through a powder metallurgical technique. The magnesium alloy contains 3% aluminum and 1% zinc. Our research aims to understand the mechanical and tribological behaviors and the impact of Electrical Discharge Machining (EDM) process parameters on AZ31 magnesium alloy. We need to modify these properties for various applications. Many industrial researchers have studied the machinability of magnesium alloys using EDM. We conducted wear tests on AZ31 alloy reinforced with both B4C and MoS2 in altered quantities using a pin-on-disc setup. The outcome displays that the wear resistance of these composites is considerably better matched to other magnesium matrix composites (MMCs). We also measured various densities of the hybrid composite, including apparent density, green density, and sintered density, which were found to be 0.839, 1.495, and 1.504 g/cm3, respectively—better than other composites. In addition, the hybrid composite exhibited a substantial increase in micro hardness, reaching 22.012 HV, indicating improved wear resistance of the material. Comparatively, low density, minimum wear profile, and maximum hardness were recorded for the sample of AZ31 + 5%MoS2 + 5%B4C. The influence of EDM parameters was discussed

Comprehensive insights on mechanical properties of natural–synthetic fibers with MWCNT nano-composite

The purpose of this study was to see how silane treatment affected the tensile and impact strength of composites constructed from jute/kenaf/glass fibers with a nano-graphene filler and to investigate the impact of major treatment factors, such as silane concentration, immersion duration, and nano-filler, on composite characteristics. To conduct systematic trials and improve these variables, the Response Surface Methodology (RSM) with central composite designs was used. To precisely forecast the tensile and impact strength of the nano-composite following silane treatment, quadratic models were built. By changing the silane concentration, immersion period, and nano-filler, they discovered ideal conditions for increasing tensile strength. The best ranges for silane concentration and immersion duration were discovered to be 15 wt. % and 30 min, respectively. Given the conditions, the composite impact strength increased by 51% and its tensile strength improved by 22% as compared to the values achieved from RSM optimization. These results highlight the practical importance of silane treatment, especially in improving tensile and impact strength and strengthening the interfacial adhesive characteristics of organic fibers and polymer matrices

Investigation of chemically treated jute/kenaf/glass fiber with TiO2 nano-filler for tensile and impact characteristics

The essential objective of this work was to investigate the effect of silane treatment on the tensile and impact strength of composites made of jute/kenaf/glass fibers with the TiO2 nano-filler. This study also sought to optimize the factors connected with this treatment method. To develop and evaluate trials, the researchers used Response Surface Methodology (RSM) with central composite designs, emphasizing the optimization of silane concentration, immersion time, and nano-filler content. The researchers were able to effectively create quadratic models to forecast the tensile and impact strengths of the nano-composite throughout the silane treatment procedure. The adjustment of silane concentration, immersion duration, and nano-filler content discovered the best conditions for obtaining maximum tensile strength. The optimal values for silane concentration and immersion time have been identified to be 15 wt. % and 30 min, respectively. Considering these conditions, the composite’s tensile strength increased by 32.13% and its impact strength improved by 8.34% above the lowest values achieved from RSM optimization. The results demonstrate the practical value of silane treatment, notably in boosting tensile and impact strengths while enhancing interfacial adhesive among natural fibers and polymer matrices

Exposure assessment to high-traffic corridors in bogota using a near-road air quality model

Vehicular traffic in Bogota is one of the main causes of air pollution, therefore it is necessary to estimate concentration levels at which the population is exposed near roads. This work summarizes the implementation of the near-road air quality model R-LINE in Bogota. Emissions from vehicles were calculated for 12,725 road links (912 km of principal roads) and assigned to the model in (g m s ) units. Meteorological information was obtained from the Bogota’s Air Quality Monitoring Network (BAQMN) stations. Evaluation of model was performed by comparing modeling outputs against pollutant observations from the BAQMN. Results suggest a good model performance and potential to use the model to evaluate personal exposure and assess/develop emission reduction strategies for improving air quality in a large metropolitan area. −1 −