Browse Topic: Manufacturing processes
This organizational process survey provides insight into the technical aspects of approved airworthy aircraft modifications applied in government organization vertical lift flight test. The publication reviews processes applied by the National Research Council of Canada's Flight Research Laboratory (NRC-FRL) and its Airworthiness Control System to enable research flight testing. Dominated by the need for integrating experimental payloads, the NRC-FRL embeds a Design and Fabrication Service organization for modification of internal and external client projects and flight test aircraft. In context of experimental flight testing, this work reviews technical information on process, facilities, and methodology for airworthy integration of flight test payloads. Information is used to synthesize recommendations in experimental vertical lift flight testing that satisfy both formal (regulated compliance) and informal (compliance intent) airworthiness requirements.
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Stretch broken carbon fiber (SBCF) offers enhanced formability as compared to continuous carbon fiber (CCF). However, robust, quantitative evaluation of forming defects remains a challenge. This study introduces a unified formability index (UFI) that integrates multiple defect types, including texture anomalies, bridging, wrinkling, thickness variation, spring-back, and resin distribution variation (RDV), into a single weighted score. Each defect is ranked on a scale of 0-5 using normalized metrics with a tunable parameter, α, allowing users to balance defect magnitude and frequency as desired. The full scoring pipeline is demonstrated for texture defects using measured data, while normalized legacy scores from previous work are used for non-texture defects to enable complete formability index computation. Case studies on three laminates illustrate how variations in α affect both texture scoring and the overall formability index and demonstrate the geometry-agnostic nature of the updated ranking and UFI systems. This framework maintains compatibility with existing evaluations while offering improved resolution, consistency, and scalability for assessing laminate quality across complex geometries.
Hybrid additive manufacturing (AM) and subtractive manufacturing (SM) processes utilize the combination of AM (e.g., LPBF and DED) and SM (e.g., milling and turning operations) to produce the final part. Due to the poor surface roughness resulting from the uneven melting of powders in AM, the subtractive process is a necessary finishing operation to improve the surface roughness of the AM part. The hybrid AM/SM technology combines the benefits of AM and SM processes to create complex geometry while introducing good surface finish and compressive stress to prevent crack initiation. However, the relationship between large process parameter space and the residual stress/distortion in the part is not well understood, which impedes the adoption of hybrid AM/SM to minimize the residual stress in the final product. To expedite the process optimization, we establish a pipeline for the sequential modeling of additive manufacturing (AM) and subtractive manufacturing (SM) processes. Key accomplishments achieved under this study include (1) development of thermal abstraction technique for the AM process to speed up the macroscale level heat transfer analysis based on the manufacturing factors including scanning vector, laser power, dwelling time, etc.; (2) development of the sequentially coupled thermal-mechanical model to predict the residual stress and distortion after AM process by passing the temperature history obtained from heat transfer analysis to the mechanical analysis at each time point; (3) validation of the thermal-mechanical model for AM using thin-wall structure from literature and cantilever beam structure from UNT’s experiments data; (4) conduction of the parametric study on the chamber temperature and part design in the AM process to demonstrate how the temperature gradient and supporting structure affect the residual stress and distortion; (5) exploration of macro and micro scale models to predict the bulk and surface residual stress after cutting; (6) applying the developed modeling framework to tailoring the hybrid AM/SM process. To support model verification and demonstration, we print cantilever beam structure with different supporting structure designs and cutting strategies to study how these factors affect the final part residual stress and distortion. The data collected in the printing and cutting process is used to examine the applicability of the developed simulation tool.
The work done in developing stretch broken carbon fiber technology is described. The objectives of the program include the scale up of the process to demonstrate production feasibility, as well as reducing the maximum filament stretch break length to ~50mm/2” or below, less than half of what was achieved on previous programs. The shorter break length is considered to be critical in order to achieve formability into complex geometries. The new stretch break line at Montana State University, BC3, has been commissioned to achieve the required material characteristics and throughput. To date, 6 tows have been successfully stretch broken simultaneously, representing a significant improvement compared with what was achieved on previous programs. Possible geometries and forming evaluation methods are described. Mechanical testing is to be conducted, including both equivalency testing of continuous vs stretch broken carbon fiber and a later minimal level allowables program. It is expected that there will be no strength reduction when using SBCF in a cured laminate as was the case on the prior programs; this will be verified under the current program with material from the new BC3 stretch break line. Single tow SBCF spools will shortly be available for evaluation by potential prepreg manufacturers and other end users.
The demand for carbon fiber reinforced polymers (CFRPs) is growing, especially for use in high-performance applications. Components manufactured of CFRP are made by layering sheets of carbon fibers within a resin matrix. Due to the fibers’ brittle nature, CFRPs are difficult to shape into complex forms, limiting adoption of the material in applications such as vertical lift systems. To address this limitation, researchers at Montana State University, Bozeman (MSU) are developing a new form of carbon fiber called stretch broken carbon fiber (SBCF). SBCF maintains the strength of continuous carbon fibers, while allowing for fiber slip that is used to create a pseudo-plastic strain response needed in most forming processes. Dome and bulge tests were used for comparing the formability response of IM7 MSU SBCF/977-3 with continuous Hexcel IM7 12K/977-3. Results showed increased formability of the MSU SBCF ones due to their ability to stretch under an applied load.
Blade–wake interaction (BWI) is a significant source of broadband noise and is often dominant in rotors with high blade counts. Accurately capturing the resulting unsteady blade loading is computationally expensive and, therefore, drives the cost of BWI noise calculation. To address this challenge, a low-fidelity BWI noise prediction tool was developed using aerodynamic data from the blade element momentum theory (BEMT) and the lattice Boltzmann method (LBM) for a series of rotor configurations with medium to high solidity. Starting from a six-bladed baseline rotor, 13 additional configurations were generated by varying blade twist, taper, root collective, solidity, and blade count. The relationship between vortex miss distance and blade loading unsteadiness was quantified to construct a semi-empirical BWI noise model. The model predicted BWI noise with a root mean square error of 3.9 dBA and a mean absolute percentage error of 1%. It was subsequently integrated into a BEMT framework to produce aerodynamic and acoustic data for training a tandem neural network (TNN) that was employed to optimize two rotor geometries. The optimized designs achieved up to a 7% reduction in BWI noise and a 7% improvement in performance. Additional geometric modifications—including blade tip anhedral, forward sweep, and a mixed configuration—were also assessed using LBM, each demonstrating notable noise reduction.
Maintaining the operational readiness of military helicopters demands repair solutions that are fast, reliable, and adaptable. This paper presents the integration of Gamma Alloys' advanced metal matrix composites (MMCs) into additive manufacturing (AM) techniques - specifically Cold Spray and Friction Stir Additive Manufacturing (FSAM) - as a transformative approach to helicopter repair and replace for the US Army.
We extend the previously developed integrated VABS (iVABS) framework for rotor blade structural optimization with an enhanced cross-section template for practical manufacture considerations; these include the introduction of curved spar corners, a continuous wrap-around skin, trailing-edge tabs and a conformal non-structural mass. The added fidelity is exercised on a UH-60A-based outer mold line through three multi-objective optimization case studies, including a case where the cross-sections are optimized independent of each other, and two cases where all the cross-sections are optimized simultaneously with manufacture considerations. It was found that the latter cases produce straight spars that are relatively more practical to manufacture when compared to the first case, while achieving significant reduction of up to 80% in the mismatch of stiffness values, inertia properties, and shear center locations, when compared to the prior work. A subsequent sensitivity analysis of the Pareto set isolates five critical combinations of design variables, out of the original nearly 100 variables, such as root/mid-span skin-ply count and spar-web placement, that can be adjusted to refine the Pareto solution. The study demonstrates that manufacturability-aware parameterization and data-driven variable reduction can deliver practical composite-blade designs within a scalable optimization loop.
ABSTRACT Today’s combat vehicle designs are largely constrained by traditional manufacturing processes, such as machining, welding, casting, and forging. Recent advancements in 3D-Printing technology offer tremendous potential to provide economical, optimized components by eliminating fundamental process limitations. The ability to re-design suitable components for 3D-printing has potential to significantly reduce cost, weight, and lead-time in a variety of Defense & Aerospace applications. 3D-printing will not completely replace traditional processes, but instead represents a new tool in our toolbox - from both a design and a manufacturing standpoint.
Prior to 1950, use of the helicopter for evacuation was extremely limited, as military top brass often considered it a worthless contraption; thus, rescue was uncertain at best for downed pilots and wounded soldiers stranded behind enemy lines. However, this all changed in Korea, where twelve U.S. Army helicopters from three detachments, working in tandem with seven, newly created Mobile Army Surgical Hospital (MASH) units, would fundamentally change the Army's medical-evacuation doctrine forever. Using several models of the Bell H-13, the Hiller H-23, and the Sikorsky H-5 and H-19, this small band of courageous pilots pushed themselves and their aircraft to their limits, transporting 21,212 critically wounded soldiers for life-saving surgery to various MASH units, cutting the fatality rate from World War II in half. Adopting the 3rd Air Rescue Squadron's motto, "That Others May Live," these pilots and their helicopters were affectionately known to the wounded as "Angels of Mercy."
The succession of the BK117 D-2 main rotor concept from the semi-rigid rotor to the BK117 D-3 bearingless main rotor (BMR) system, derived from the H135, held many new and innovative additional benefits in its wake. Although the H135 system is the best on the market regarding maintenance effort and maintenace cost (DMC), it was the purpose to push this benchmark even further. To achive additional benefits, three major improvements needed to be successfully implemented and none of them was a given. First to mention is the concept of the blade being separated in three parts. In case of foreign object damage (FOD), most of the time only the outer part needs to be repaired. In parallel a new possibility to fold the system with a full folding capacity was introduced with the challenge to realize the extremely low DMCs of the H135, in a decisively bigger helicopter and to benefit from the experience of millions of flight hours and thousands of helicopters operated throughout the world. Second a reduced flapping hinge offset was introduced to improve the comport of ride. The third point is the attachment bearing stress laminate providing the benefit of slim shape in the connection area between Flex control unit (FCU) and blade airfoil section. All this with the reduction of vibration in mind that results from changing a four-bladed rotor to a five-bladed one [1]. We were motivated to include also a, for such kind of critical part, new liquid infusion molding technology, to have all process parameters in our own hands, to make the production of blades more reliable and at the same time reduce the number of nonconformities by introducing more and more automation in production, which was enabled using the bearing laminate design of the attachment [2]. This innovative new design, in combination with a new manufacturing process introduced in a different production site under considerable time and cost pressure, needed the dedication of a multi-disciplinary transnational team, to finally overcome all deviations that became visible throughout the industrialization and/or prototype phase. This finally led to a mature serial production within a two years time frame. The paper is intended to highlight the often shortened and only briefly recognized period of preproduction, prototyping and the serialization and maturation of critical composite parts.
In the proposed article, the authors will focus on two manufacturing method FUSED FILAMENT FABRICATION (FFF) and FUSED DEPOSITION MODELING (FDM) showing examples of application in aviation production and the resulting benefits.
The Autoclave processing is commonly used in manufacturing high-performance fibre-reinforced thermoset composite components in the aerospace industry. Variations in the cure cycle, sometimes even apparently minor deviations from the prescribed cure cycle, can harm the laminate properties. Given the costly and time-consuming autoclave manufacturing process, there is a strong need to cure the maximum number of parts in the shortest possible time without compromising quality. In order to achieve high-rate automated manufacturing with the optimized autoclave process, it is important to construct a digital twin modelling approach to mirror the physical composite curing process in the virtual domain based on the integration of high-fidelity multi-physics models. The resulting digital twin includes a thermal CFD model, a thermo-chemo-mechanical module, and an efficient and accurate block coupling between these two modules. The customized Abaqus driven by local and spatial variation of the turbulence-induced heat transfer coefficient (HTC) imposed through one-way coupling determines the thermo-mechanical response in composite parts. Using the developed digital twin tool (SMARTCLAVE), HTC's spatial and temporal variation can be generated digitally without invoking an expensive and time-consuming experimental approach. The predicted local boundary conditions are used in SMARTCLAVE to determine the cure kinetics, temperature distribution, and thermal-mechanical response that drives the residual stress and distortion of composite parts after curing. The accuracy of the digital twin for autoclaving is demonstrated first using a benchmark problem followed by the capability demonstration with a single-part L-beam assembly. The benefits of using the digital twin tool are illustrated via the optimal placement of multiple parts in an autoclave to balance the throughput and quality.
This white paper discusses the application of carbon fiber roving for rotor magnet retention in high-performance Brushless DC (BLDC) motors, focusing on sectors like Advanced Air Mobility and motorsports. Highlighting the benefits of carbon fiber's tensile strength, thermal characteristics, and electrical resistivity, it compares thermoset and thermoplastic matrices, analyzing their trade-offs. It delves into manufacturing methods, particularly the advantages of in-situ winding of Hexcel® HexTow® IM7 12k carbon fiber directly onto rotors, versus pre-wound sleeves, emphasizing controlled processes for even stress distribution and preventing failure. Key design factors such as operating speed, temperature, and air gap dimensions are considered to optimize carbon fiber's application. Windings' expertise in fabricating high-tolerance carbon fiber wound rotors is showcased, highlighting its potential to enhance motor power output and offering collaboration for innovative retention solutions in BLDC motors.
Thermoplastic composites are serious competitor for classic epoxy composites. They have comparable properties to epoxy composites, but characterize much lower processing costs. There are several methods of manufacturing the components from thermoplastic composites. One of the most interesting method in terms of efficiency is thermoforming on a press. This technology allows to product of the aircraft parts such as: ribs, brackets, covers, stiffeners. Thermoplastic composites are resistant to most solvents such as grease, oil and aviation fuel. They are also non-flammable and heat-resistant. This all makes them suitable for use in aircraft as upholstery, casing or elements around the tank. PZL Mielec has been developing press thermoforming technologies since 2016 and is the owner of the several patents in this area.
Quenching is a heat treatment process for the rapid cooling of a metallic workpiece in water, oil, or air to obtain certain desired material properties. It is the most critical step in the sequence of heat-treating operations to preserve the solid solution formed at the solution heat-treating temperature by rapidly cooling to near room temperature. Because of the complex interaction between temperature, phase-transformation, and stress/strain relation that depends on the temperature distribution and the microstructure of the workpiece, there is no performance-informed quenching process that can be applied reliably to reduce the high scrap rate of airframe aluminum forging parts with a significant amount of residual stress and distortion. Since large aluminum forging parts are increasingly used in aerospace structures to enable structural unitization, it is important to construct a digital twin modeling approach to mirror the physical quenching process for minimizing scrap rate, increasing production efficiency, and engineers and machine operators' handling of variances in forging operations. A high-fidelity modeling of the coupling of thermal, metallurgical, and mechanical interactions is a key component to creating a digital twin of the physical quenching process. A high-fidelity thermal multi-phase computational fluid dynamics (CFD) model is applied to simulate fluid dynamics and temperature fields in the quenchant tank. The developed immersogeometric modeling approach is used next for an efficient model generation of a 3D workpiece with various dipping orientations. Given the temperature and pressure profiles predicted from the CFD-based heat transfer module, residual stress and distortion prediction modules are developed by including temperature and pressure fields mapping and temperature and strain rate dependent property evolution via Abaqus' user-defined subroutines. Verification and demonstration studies are performed using aluminum coupons dipped into a quenching tank with different orientations. Time histories of the temperature and residual stress fields were predicted to explore the relationship between the process and performance.
Over 4 decades of research works on the nutating, now pericyclic, mechanical transmission have studied its capability to achieve high power density, low noise, and amplified single-stage reduction ratios of up to 100:1. These analytical efforts have culminated into the fabrication of a 50 HP and 32:1 reduction ratio pericyclic transmission prototype. This work introduces the prototype with highlights of the assembly and alignment procedures validated by static testing evaluation. Then, discussion of the dynamic test stand integration, instrumentation, and lubrication components lay out the framework of the high-speed testing plan. Power transmission data validated the pericyclic reduction ratio model. Accelerometer data demonstrated the transmission's capability to operate at low vibration, with peak amplitudes of 1.2 and 2.5 inches per second on the pericyclic gear train and output shaft respectively. Acoustic emission data captured the first 5 harmonics of the shaft speed as well as gear mesh frequencies. The thermal profile showed the shaft bearings remained below 180°F throughout testing, implying safe operating conditions. Finally, strain and vibration data showed the pericyclic gear train maintained load sharing throughout the entire operating envelope, further validating static testing and assembly procedures. The results of the experiments demonstrate the technological readiness of pericyclic mechanical transmission.
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