Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
Browse
5 results
Search Results
Item Effect of process variables on the uncured handleability and formability of stretch broken carbon fiber(Montana State University - Bozeman, The Graduate School, 2022) Rezaul, Riad Morshed; Chairperson, Graduate Committee: Cecily A. RyanCarbon fiber is a high-performance reinforcing material used extensively in aerospace composites. Although carbon fiber is used in both continuous and discontinuous form, the continuous carbon fiber is limited by its inability to stretch due to its low strain to failure during manufacturing structures with complex geometries. Stretch broken carbon fiber (SBCF) is a type of discontinuous and aligned carbon fiber which has the potential to solve this limitation of inextensibility of its continuous counterpart. The discontinuous nature of SBCF enhances its stretchability making this material a prime candidate for manufacturing parts with complex curvatures. SBCF is generated by stretching the fibers using a pair of differentially driven rollers, which breaks the fibers at their intrinsic flaws. Although SBCF can be stretched due to being discontinuous, it compromises the tensile strength due to the lack of fiber continuity. Therefore, a polymeric coating known as sizing is applied to the SBCF to reconstruct its tensile strength. In the context of SBCF production, sizing serves two important functions. Firstly, sizing provides uncured carbon fiber the desired handleability and back-tension ability. Secondly, sizing enhances the formability of SBCF, which is a defined as the ease at which a material can be formed into a desired shape without failure. The goal of this work is to investigate the effect of process variables on the generation of stretch broken carbon fiber with consistent and repeatable material properties. The stretch broken carbon fiber research group at Montana State University (MSU) has developed a stretch breaking machine known as 'Bobcat' to generate single tow MSU SBCF. The noteworthy process variables related to MSU SBCF production includes sizing deposition on the tow, stretch ratio, nip force, line speed, fiber length distribution, and tow tenacity. Target amount of sizing deposition on MSU SBCF tow was achieved by choosing an appropriate sizing bath. A temperature-controlled tow tenacity result suggests that MSU SBCF possesses adequate handleability, back-tension ability and formability. MSU SBCF also shows a narrow fiber length distribution and relatively short mean fiber length which indicate improved formability. Reproducibility of these results were observed in the replicate batches of MSU SBCF. Suitable stretch ratio and nip force regimes were identified to optimize MSU SBCF production.Item RadPC@Scale: an approach to mitigate single event upsets in the memory of space computers(Montana State University - Bozeman, College of Engineering, 2022) Williams, Justin Patrick; Chairperson, Graduate Committee: Brock LaMeresThis thesis presents the flight test results of a single event upset (SEU) mitigation strategy for computer data memory. This memory fault mitigation strategy is part of a larger effort to build a radiation tolerant computing system using commercial-off-the-shelf (COTS) field programmable gate arrays (FPGAs) called RadPC. While previous iterations of RadPC used FPGA block RAM (BRAM) for its data memory, the specific component of RadPC that is presented in this paper is a novel external memory scheme with accompanying systems that can detect, and correct faults that occur in the proposed data memory of the computer while allowing the computer to continue foreground operation. A prototype implementation of this memory protection scheme was flown on a Raven Aerostar Thunderhead high-altitude balloon system in July of 2021. This flight carried the experiment to an altitude of 75,000 feet for 50 hours allowing the memory in the experiment to be bombarded with ionizing radiation without being attenuated by the majority of Earth's atmosphere. This thesis discusses the details of the fault mitigation strategy, the design-of-experiments for the flight demonstration, and the results from the flight data. This thesis may be of interest to engineers that are designing flight computer systems that will be exposed to ionizing radiation and are looking for a lower cost SEU mitigation strategy compared to existing radiation- hardened solutions.Item Forming evaluation metrics and methods for complex stretch broken and continuous carbon fiber parts(Montana State University - Bozeman, College of Engineering, 2023) Dube, Madison Eve; Chairperson, Graduate Committee: Cecily RyanCarbon fiber composites are an ideal material for aircraft structures due to their light weight and high strength and stiffness. Traditional continuous carbon fiber composites are limited by their ability to form into complex geometric features as they have minimal abilities to stretch into a mold. Stretch broken carbon fiber is discontinuous which allows for the different tows of carbon fiber to slip relative to each other allowing for laminate displacements unattainable to continuous carbon fiber. In order to develop and improve stretch broken carbon fiber manufacturing processes, a method is developed herein to analyze the forming quality of a complex carbon fiber part. This method quantifies common qualitative forming metrics by measuring, evaluating, and scoring carbon fiber defects including: bridging, wrinkling, variation in thickness, forming depth, corner thinning and thickening, resin pooling, and additional texture defects. The scores produced from evaluating the various forming metrics on formed carbon fiber parts are assembled in a weighted matrix to produce an overall forming score. This forming evaluation method is demonstrated on three different geometric mold designs to assess that it is quantitative, repeatable, accounts for many carbon fiber defects, and accounts for discrepancies between the formed part and the designed part. This method was also tested on different carbon fiber prepreg materials: MSU SBCF/Cycom 977-3 resin from Solvay, MSU SBCF/Hexcel 8552, and Hexcel IM7/8552. Through testing, the method is found to have achieved the method design goals as well as ascertaining areas of improvement for MSU SBCF prepreg which is still under development. Results show that stretch broken carbon fiber and traditional continuous carbon fiber achieve similar overarching forming scores, but outperform one another in different category metrics. MSU SBCF has higher scores in corner thickening and resin pooling; continuous carbon fiber has higher scores in wrinkling and bridging. The method forms the foundation to evaluate layup practices and autoclave cure cycles when systematically applied in a process development setting. This method is also extendable to dissimilar geometric part types with modifications in suitable metrics.Item Forming parameters and quantification of continous and stretch broken carbon fibers(Montana State University - Bozeman, College of Engineering, 2021) Janicki, Joseph Charles; Chairperson, Graduate Committee: Dilpreet S. Bajwa; This thesis contains two articles of which Joseph Charles Janicki is not the main author.Continuous carbon fibers are premium reinforcing material for aerospace composites. Carbon fiber reinforced polymers are five times stronger than steel and twice as stiff, making it an ideal candidate for structural aircraft components where weight is an important factor. The challenge with continuous carbon fibers is their difficulty to form deep drawn parts requiring intricate manufacturing techniques that increase manufacturing time, cost, and material waste. An alternative to continuous carbon fibers is stretch broken carbon fiber (SBCF). SBCF is a form of aligned discontinuous fiber, it has been proposed as an alternative to overcome this formability challenge. SBCF provides flexibility to form complex shapes while maintaining comparable strength and stiffness. A variety of testing methods have been developed to study both the ability of SBCF to form over traditional continuous carbon fiber and how different iterations of SBCF perform against each other. These include testing carbon fiber tows in tension on a universal test stand as well as designing and creating a forming tool that tests resin impregnated tows under different geometry conditions and temperatures. Tensile properties of both a continuous tow and a SBCF tow were evaluated at different gauge lengths and temperatures. It shows that SBCF tow maximum load increases as the gauge length decreases as well as elevated temperature has a clear effect on the tensile properties when fiber continuity is considered. Cross-sectional areas of continuous and SBCF tows were calculated using both areal weight and scanning electron microscopy showing that in general continuous fiber tows have a larger cross-section than SBCF. Using a forming fixture to test samples, results were statistically analyzed in order to display the significance of geometry and temperature on the maximum forming load of different fibers. The suite of testing and results indicate that in general SBCF maintains superior formability to that of continuous fibers. Overall lower maximum force is required for SBCF to form into deep drawn shapes. This supports their ability to be used more readily in complex aircraft structure while minimizing the disadvantages posed by traditional carbon composites.Item A fault-tolerant computer architecture for space vehicle applications(Montana State University - Bozeman, College of Engineering, 2012) Hane, Jennifer Susan; Chairperson, Graduate Committee: Brock LaMeresThe discovery of new methods to protect electronics from harsh radiation environments outside earth's atmosphere is important to the future of space exploration. Reconfigurable, SRAM-based Field Programmable Gate Arrays (FPGAs) are especially promising candidates for future spacecraft computing platforms; however, their susceptibility to radiation-induced faults in their configuration memory makes their use a challenge. This thesis presents the design and testing of a redundant fault-tolerant architecture targeted at the Xilinx Virtex-6 FPGA. The architecture is based on a combination of triple modulo redundancy (TMR), numerous spare units, repair (scrubbing), and environmental awareness. By using the spares and the partial reconfiguration capabilities of the FPGA, the system can remain operational while repair of damaged modules proceeds in the background. The environmental awareness is supplied by a multi-pixel radiation sensor designed to rest above the FPGA chip, providing information about which areas of the chip have received radiation strikes. The system places these potentially damaged areas first in the queue for scrubbing. Four implementations of the architecture with different types of computing module and numbers of spares reveal its versatility and scalability. These four demonstration systems were modeled with theoretical Markov calculations, for the purpose of determining their reliability. They were also implemented on Xilinx hardware and tested by the injection of simulated faults, based on realistic orbital fault rate data from the Cosmic Ray Effects on Micro-Electronics Code (CREME96) tool. These results confirm that the systems will be highly reliable under typical earth orbit conditions. The results also demonstrate that the inclusion of numerous spares and the sensor both lead to substantial improvements in the Mean Time Before Failure, over a traditional TMR system with only three modules and scrubbing.