Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Forming properties of stretch broken carbon fiber for aircraft structures(Montana State University - Bozeman, College of Engineering, 2023) Nold, Dalton Bradley; Chairperson, Graduate Committee: Dilpreet S. Bajwa; Douglas S. Cairns (co-chair); This is a manuscript style paper that includes co-authored chapters.Continuous carbon fiber is known to be a superior material for its strength, stiffness, and high strength-to-weight ratio and is often incorporated in aerospace composites. A challenge, however, is that it's not versatile in forming deep drawn geometries, which require convoluted manufacturing techniques resulting in expensive components. To overcome this, a type of carbon fiber with a random discontinuous fiber alignment called stretch broken carbon fiber (SBCF) is proposed. SBCF has potential to form parts with complex geometries with comparable or better mechanical properties to that of continuous carbon fiber. Montana State University (MSU) developed its own version of SBCF manufacturing processes, and research is being conducted to understand how SBCF prepreg tows react to stretch drawing at elevated temperatures using aerospace-grade epoxy resin systems. Currently, several new methods have been proposed to rapidly test these materials. This research revealed that SBCF forms with greater ease than continuous carbon fiber and is expected to substantially reduce manufacturing times for aircraft structures. To comprehend the material's behavior, simple tensile tests were coursed to understand how gauge length and temperature affected the peak loads when compared to continuous carbon fiber. It was discovered that on average, SBCF experienced stresses that were ten times less than continuous fibers. Additional tensile tests were conducted at elevated temperature to determine the true stress versus true strain. These tests are particularly important because they represent the material's most accurate mechanical properties. The results led to the discovery that SBCF experienced strain softening behavior. Furthermore, a series of forming tests using a novel "forming fixture" revealed that increasing the gap lowered the peak forming loads while the plunger geometry had little to no effect on peak forces at both room and elevated temperatures.Item Cessna 182b windscreen material model development and full scale UAS to aircraft impact testing facility(Montana State University - Bozeman, College of Engineering, 2020) Arnold, Forrest Jacob; Chairperson, Graduate Committee: Douglas S. CairnsUnmanned Aircraft Systems (UAS) have become popular in the last decade. More than 1.5 million have been registered by the Federal Aviation Administration (FAA) since 2015. In order to understand the risk UAS pose to manned aircraft and make informed regulation decisions, the FAA has created air to air collision studies. As a part of the FAA general aviation air to air collision research, a Cessna 182 windscreen material model and a full scale impact testing facility were required. A Finite Element Crash Model of a Cessna 182 is in development as a part of the general aviation air to air collision research. The National Institute for Aviation Research at Wichita State University is managing development of the model. In support of that work, an LS-DYNA material model of the Poly(Methyl methacrylate) windscreen was developed. Results from tensile testing at multiple strain rates were used to develop material models using MAT_124 and MAT_187. A model of an impact tower was created to compare the material models to test results. The material models were tuned to better fit the impact tower test results. MAT_187 has more flexible material inputs, which allowed it to outperform MAT_124. A full scale impact testing facility was developed to support Finite Element model validation and direct testing of UAS to aircraft impact. A slingshot style launcher was designed and built to launch common quadcopter style UAS. Testing has shown that the launcher is capable of 120 knots with the accuracy required to repeatably hit the leading edge of a wing. Additionally, the launch site required a system for instrumented testing to compare experimental results with finite element results. A system was developed to allow flexible fixturing, impact speed and orientation measurement, and inclusion of load cells and strain gauges.