Browse Topic: Carbon fibers
With performance advances proposed for the Future Vertical Lift suite of aircraft and advancements in the electronic battlefield, it is imperative that advanced materials and concepts be included in the vehicle designs to meet the aggressive weight reduction objectives, structural requirements, and operational environment capabilities. Integrating electromagnetic (EM) shielding during the design process offers an opportunity to make progress towards the performance goals. To this end, efforts must be made to minimize the impact of this shielding to platform weight and structural performance. This article presents work to develop a hybrid multifunctional composite material technology that incorporates copper mesh into a carbon fiber and thermoplastic matrix structural composite material to achieve required levels of EM shielding and high levels of structural efficiency while reducing the overall weight of the system. This article focuses on the design of a representative helicopter
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
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.
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
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
Carbon fiber reinforced epoxy composite stiffened panels are increasingly being used for structural components in large transport rotorcraft. However, problems are arising with high levels of vibration and interior noise due to the increased stiffness-to-density ratio of composites. The current investigation explores the potential of reducing vibrations in carbon/epoxy stiffened panels with the integration of acoustic black holes (ABH), namely features that incorporate a power law thickness taper. The proposed approach involves designing a taper into the thickness of the blade stiffeners as well as the thin plate. Integration of ABHs into the fuselage structure has the potential to reduce broadband vibrations. Multiple parametric studies with either an ABH integrated into the blade stiffener or a grid of ABHs integrated into the plate were conducted, and the tradeoffs between vibration amplitudes, panel mass, and compressive buckling load were examined. Carbon/epoxy panels were
ABSTRACT
The complex dynamics of rotorcraft structures under varying operational and environmental conditions demand the development of accurate and robust-to-uncertainties structural health monitoring (SHM) approaches. The inherent uncertainty within monitoring data makes it difficult for conventional methods to accurately and robustly detect and quantify damage without the need for a large number of data sets. In addition, due to the time-varying nature of rotorcraft operations, such conventional metrics might still fail even with abundance of data. In this paper, we propose a unified probabilistic damage detection and quantification framework for active-sensing, guided-wave SHM that focuses on monitoring rotorcraft structural "hotspots". The proposed framework involves three stages: The first stage incorporates statistical damage detection based on stochastic non-parametric time series (NP-TS) models of ultrasonic wave propagation signals within a hotspot sensor network configuration. The
Carbon fiber reinforced polymer composites (CFRP) are extensively used as structural components in rotorcraft applications. Here, we report considerable improvement in the fatigue life of CFRP through the infiltration of nanoscale silica particles into the epoxy resin matrix (nanoCFRP). Fumed silica nanoparticles were initially added to the epoxy resin to prepare epoxy-silica nanocomposites, which were demonstrated to have superior fracture and fatigue properties. Fractographic analysis indicated presence of various key toughening mechanisms including crack deflection, plastic void growth as well as a hitherto unreported heterogeneity induced mesoscale toughening effect. The epoxy-silica nanocomposite resin was then used as the matrix material to fabricate nanoCFRP. Cyclic flexural bending tests indicate significant fatigue life enhancement for the nanoCFRP. The enhancement is especially pronounced in the high cycle fatigue regime. This enhancement in high cycle fatigue is indicative
Bismaleimide (BMI) resins are commonly used in advanced carbon composites for their high service temperature and excellent mechanical properties. In this study, two different BMI resins were compared: 1) formula RS-8HT, a high-cure temperature resin requiring pressurized consolidation, and 2) formula BMI-2, a lower cure temperature resin compatible with vacuum bag only fabrication. The objective was to identify a suitable high-temperature resin system for hybrid aerospace gear application, however, these materials are applicable to a variety of hot-zone parts. Laminates were fabricated from each resin type and characterized by their fiber volume fraction, compression strength vs. temperature, and glass transition temperature (Tg). Optical microscopy was performed to verify laminate quality. It was found that the carbon/RS-8HT laminates were prone to thermally-induced cracking, especially during post-cure. Carbon/BMI-2 laminates were found to attain a high degree of cure and high Tg
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