Guided Wave-Based J-Integral Estimation For Dynamic Stress Intensity Factors Using 3d Scanning Laser Doppler Vibrometry, J. Ayers, Christopher Todd Owen, Eric D. Swenson, Anindya Ghoshal, V. Weiss

Faculty Publications

The application of guided waves to interrogate remote areas of structural components has been researched extensively in characterizing damage. However, there exists a sparsity of work in using piezoelectric transducer-generated guided waves as a method of assessing stress intensity factors (SIF). This quantitative information enables accurate estimation of the remaining life of metallic structures exhibiting cracks, such as military and commercial transport vehicles. The proposed full wavefield approach, based on 3D laser vibrometry and piezoelectric transducer-generated guided waves, provides a practical means for estimation of dynamic stress intensity factors (DSIF) through local strain energy mapping via the J-integral. Strain energies …

Investigation Of Astm E 238 Bearing Pin Properties For Various Aerospace Alloys, Trevor J. Lee

Master's Theses

Aircraft are often designed with numbers determined by testing in a lab, rather than by repeatedly building prototypes. These lab tests conform to testing specifications so that the numbers can be compared between manufacturers, suppliers, and lab technicians. One such specification is ASTM specification E238 – 84(08), and it is used to determine important properties of a bearing pin joint like hinges, bolt holes, and rivet joints. The properties determined from this fastener-through-plate method are bearing strength, bearing yield strength, and bearing stiffness.

Adhering to the methods outlined in ASTM E238, a study was performed, looking at the effects that …

Materials Selection And Processing Techniques For Small Spacecraft Solar Cell Arrays, Naseem M. Torabi

Theses and Dissertations--Electrical and Computer Engineering

Body mounted germanium substrate solar cell arrays form the faces of many small satellite designs to provide the primary power source on orbit. High efficiency solar cells are made affordable for university satellite programs as triangular devices trimmed from wafer scale solar cells. The smaller cells allow array designs to pack tightly around antenna mounts and payload instruments, giving the board design flexibility. One objective of this work is to investigate the reliability of solar cells attached to FR-4 printed circuit boards. FR-4 circuit boards have significantly higher thermal expansion coefficients and lower thermal conductivities than germanium. This thermal expansion …

The Effect Of Sensor Mass, Sensor Location, And Delamination Location Of Different Composite Structures Under Dynamic Loading, Albert Darien Liu

Master's Theses

This study investigated the effect of sensor mass, sensor location, and delamination location of different composite structures under dynamic loading. The study pertains to research of the use of accelerometers and dynamic response as a cost-effective and reliable method of structural health monitoring in composite structures. The composite structures in this research included carbon fiber plates, carbon fiber-foam sandwich panels, and carbon-fiber honeycomb sandwich panels. The composite structures were manufactured with the use of a Tetrahedron MTP-8 heat press. All work was conducted in the Cal Poly Aerospace Structures/Composites Laboratory. Initial delaminations were placed at several locations along the specimen, …

Effect Of Stitch Density On Tensile Properties And Damage Mechanisms Of Stitched Carbon/Epoxy Composites, Arief Yudhanto, Naoyuki Watanabe, Yutaka Iwahori, Hikaru Hoshi

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Experimental investigation is performed to study tensile properties, damage initiation and development in stitched carbon/epoxy composites subjected to tensile loading. T800SC-24kf dry preforms with tow orientation of [+45/90/-45/02/+45/902/-45/0]s are stitched using 200 denier Vectran® thread. Modified-lock stitch pattern is adopted, and stitch density is varied, viz. moderate density (stitched 6 x 6: stitch density = 2.8 cm-2) and high density (stitched 3 x 3: stitch density = 11.1 cm-2). The stitched preforms are then infiltrated by epoxy XNR/H6813 using resin transfer molding process. Tensile test is conducted to obtain in-plane mechanical properties (tensile strength, failure strain, tensile modulus and Poisson's …

Numerical Modeling And Characterization Of Vertically Aligned Carbon Nanotube Arrays, Johnson Joseph

Theses and Dissertations--Mechanical and Aerospace Engineering

Since their discoveries, carbon nanotubes have been widely studied, but mostly in the forms of 1D individual carbon nanotube (CNT). From practical application point of view, it is highly desirable to produce carbon nanotubes in large scales. This has resulted in a new class of carbon nanotube material, called the vertically aligned carbon nanotube arrays (VA-CNTs). To date, our ability to design and model this complex material is still limited. The classical molecular mechanics methods used to model individual CNTs are not applicable to the modeling of VA-CNT structures due to the significant computational efforts required. This research is to …

Elastic–Plastic Analysis And Strength Evaluation Of Adhesive Joints In Wind Turbine Blades, Yi Hua, Ananth Ram Mahanth Kasavajhala, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

The objective of this paper is to investigate the performance of adhesive joints of carbon/epoxy wind turbine blade subjected to combined bending and tension loadings through finite element method. The influence of adhesive material properties and geometrical details including fillet and imperfections was examined in terms of interlaminar stresses in the adhesive layer. The variation of stress intensity with change in adhesive shear modulus has also been investigated, while contour integral method was used for evaluating the stress intensity factors (SIF) at the imperfection tip. Furthermore, the strength of the joint was assessed through the crack initiation and propagation analysis. …

Effects Of Seawater On The Mechanical Behavior Of Composite Sandwich Panels Under Monotonic Shear Loading, Thomas Robert Woo

Master's Theses

Abstract

Salt water environments are very harsh on materials that are used within them. Many issues are caused by either corrosion and/or internal degradation to the materials themselves. Composites are better suited for this environment due to their high strength to weight ratios and their corrosion resistance, but very little is known about the fracture mechanics of composites. The goal of this study is to gain a better understanding for the behavior of a composite boat hull under a shear loading, similar to the force water applies on the hull as the boat moves through the water; then attempt to …

Manufacturing Processes In An All-Aluminum Airframe, Stewart Mcdougall

Aerospace Engineering

One often overlooked aspect to building an aircraft is the manufacturing process used to put it into production. This may be a major contributor to acquisition cost and requires a large amount of money to implement. Once all the tooling has been purchased, one of the greatest costs is labor. The experience of building an all-aluminum aircraft shows that the production process is one which may be done in many different ways. Minimizing the assembly time is important for aircraft manufacturers and one of the best ways to do that is on the assembly line itself. Specific practices in the …

Optimizing The Mechanical Characteristics Of Bamboo To Improve The Flexural Behavior For Biocomposite Structural Application, Jay Lopez

Master's Theses

Global awareness and preservation have spurred increasing interest in utilizing environmentally friendly materials for high-performance structural applications. Biocomposites pose an appealing solution to this issue and are characterized by their sustainable lifecycles, biodegradable qualities, light weight, remarkable strength, and exceptional stiffness. Many of these structural qualities are found in applications that exhibit flexural loading conditions, and this study focuses on improving the bending performance of engineered biocomposite structures. The current application of biocomposites is increasing rapidly, so this expanding research explores other natural constituent materials for biocomposite structures under flexural loading.

The renewable material investigated in this study was experimentally …

Mechanical Optimization And Buckling Analysis Of Bio-Composites, Cameron D. Chan

Master's Theses

Today’s environmental concerns have led a renewed search in industry to find new sustainable materials to replace non-renewable resources. President Barack Obama also quoted in the recent 2012 Presidential Debate “that there is a need to build the energy sources of the future and invest in solar, wind, and bio-fuels.” Bio-composites are believed to be the future and the new substitute for non-renewable resources. Bio-composites are similar to composites in that they are made up of two constituent materials; however the main difference is that bio-composites are made from natural fibers and a biopolymer matrix. This research investigates the buckling …

Structural Damage Classification Using Support Vector Machines, Xiang Li

Doctoral Dissertations and Master's Theses

In this research, a methodology to classify crack and corrosion metallic damages using a time-frequency representation method and support vector machines is investigated. Piezoelectric ceramic actuators are utilized to generate guided wave signals on a set of aluminum beam coupons with different damage features, such as types, locations, and thicknesses. The short-time Fourier transform is applied to analyze the measured signals. For damage classification, the spectrograms obtained from finite element models are employed to train a two-class support vector machine learning classifier. The classifier is able to correctly classify different types of damages based upon the measured signals collected from …

Investigation Into Suitability Of Geopolymers (Illite & Metakaolin) For The Space Environment, Brandon T. Cesul

Theses and Dissertations

Suitability of non-organic polymers for space application is studied. Materials included are illite and metakaolin. Bulk material suitability was investigated for exposure to ultraviolet radiation, atomic oxygen, and high energy charged particles. Outgassing phenomenon of the materials was studied. Curing shrinkage reduction techniques were identified as well.

Performance Effects Of Damage Arrestment Devices On Sandwich Composite Beams Under Monotonic Loading, Yvette Vanessa Wood

Aerospace Engineering

Face-core delamination has become a subject matter in the Aerospace industry, as it can lead to early failure. In this study, sandwich composite beams are tested initially with no delamination to obtain the ultimate strength. A second case of delamination in the center of the beam in initialized to verify a decrease in ultimate strength. This experiment investigates the performance effects of the addition of Damage Arrestment Devices (DADs), in composite sandwich beams. The performance criterion is measured by strength in flexural loading test. The objective of this project is to verify an increase in the strength and performance with …

Two-Stage, High-Altitude Rocket With Internal Skeleton Design Entered In Advance Category Of 7th Esra Irec, Samuel S. Bowman, Kevin J. Byrne, Allen Capatina, Aliki S. Loper-Leddy, Joshua A. Van Schoyck

Aerospace Engineering

A high-altitude, two-stage rocket was designed, built, and entered in the advanced category of the 7^th Annual Experimental Sounding Rocket Association (ESRA) Intercollegiate Rocketry Engineering Competition (IREC). The rocket, called AJAKS, featured an internal skeleton made of carbon fiber rods, and a combination of plywood, carbon, and aluminum bulkheads. Loads were driven through the internal structure, with an outer skin tube providing an aerodynamic surface. A unique separation device was developed to ensure proper stage separation. The competition required the rocket to carry a 10-lb payload, which was chosen by the team to consist of an IMU and data …

A Resistance Based Structural Health Monitoring System For Composite Structure Applications, Dennis N. Boettcher

Master's Theses

This research effort explored the possibility of using interwoven conductive and nonconductive fibers in a composite laminate for structural health monitoring (SHM). Traditional SHM systems utilize fiber optics, piezoelectrics, or detect defects by nondestructive test methods by use of sonar graphs or x-rays. However, these approaches are often expensive, time consuming and complicated.

The primary objective of this research was to apply a resistance based method of structural health monitoring to a composite structure to determine structural integrity and presence of defects.

The conductive properties of fiber such as carbon, copper, or constantan - a copper-nickel alloy - can be …

The Effect Of A Low-Velocity Impact On The Flexural Strength And Dynamic Response Of Composite Sandwiches With Damage Arrestment Devices, Kodi A. Rider

Master's Theses

Impact strength is one of the most important structural properties for a designer to consider, but is often the most difficult to quantify or measure. A constant concern in the field of composites is the effect of foreign object impact damage because it is often undetectable by visual inspection. An impact can create interlaminar damage that often results in severe reductions in strength and instability of the structure. The main objective of this study is to determine the effectiveness of a damage arrestment device (DAD) on the mechanical behavior of composite sandwiches, following a low-velocity impact. A 7.56-lb_f crosshead …

Response Surface Optimization Of Electron Beam Freeform Fabrication Depositions Using Design Of Experiments, Patricia A. Quigley

Engineering Management & Systems Engineering Theses & Dissertations

The Electron Beam Freeform Fabrication (EBF³ ) System is a material depositing, layer additive technique that produces three dimensional (3D) parts out of a wide range of metals in high vacuum, using an electron beam and wire feedstock. Screening deposition trials on a titanium alloy, Ti-6Al-4V, at the National Aeronautics Space Administration (NASA) revealed selective vaporization of the aluminum content of linear prototypes when subjected to chemical analysis. In this study, the aluminum content, bead height and bead width output responses were analyzed from a systematic study of the effects that the interactions of the EBF³ processing parameters …

Effect Of Multifunctional Material On The Mechanical Behavior Of Composite Structure Using Finite Element Analysis, Nicholas A. Romonoski

Aerospace Engineering

No abstract provided.

Development Of A Pyrotechnic Shock Simulation Apparatus For Spacecraft Applications, Joseph Binder, Matthew Mccarty, Chris Rasmussen

Aerospace Engineering

This report details the research, design, construction, and testing of a pyrotechnic shock simulation apparatus for spacecraft applications. The apparatus was developed to be used in the Space Environments Lab at California Polytechnic State University. It will be used for testing spacecraft components with dimensions up to 24”x12”x12” as well as CubeSats. Additionally, it may be used as an instructional or demonstrational tool in the Aerospace Department’s space environments course. The apparatus functions by way of mechanical impact of an approximately 20 lb stainless steel swinging hammer. Tests were performed to verify the simulator’s functionality. Suggestions for improvement and further …

Thermal Vacuum Integration For Cal Poly's Space Environments Laboratory, Chelsea Barackman, Steven Jackowski

Aerospace Engineering

The purpose of the senior project is to construct a thermal vacuum by utilizing a preexisting vacuum chamber in the Space Environments Lab, and a donated Advanced Thermal Sciences (ATS) chiller. While a thermal vacuum is already available on campus, building one for the Space Environments Lab would grant undergraduates access to the equipment, allowing a much better understanding of testing methods and procedures in use by the aerospace industry. This paper explains the design and analysis of the thermal vacuum (T-VAC) project as well as the operation and procedures required for the ATS chiller and fill/drain tank. The thermal …

A Study On Organic Epoxy And Hemp Composite Plates With An Emphasis On Mechanical And Finite Element Analysis, Alma Melendez

Aerospace Engineering

Several vibration and tensile tests were conducted for four natural fiber hemp composites in order to observe its behavior and acquire the material properties of hemp. Two plates were made on the Cal Poly press table, while the other two plates were made on the Cal Poly vacuum table. All four plates are made of 100% hemp under three different types of weave. The first plate is called CTPT-12, has a thickness of 0.053 inches, and was made on the press table. The second plate is called CTL4 with a thickness of 0.152 inches and made on the press table. …

The Study Of Natural Composite I-Beam In A Three Point Bending Test, Abdel Shabbar

Aerospace Engineering

The objective of this experiment is to conduct a series of unidirectional tensile test on several samples of natural occurring plant fibers. Among the materials tested, hemp has proven to be the most promising candidate as the base material in creating an all-natural composite I-Beam. This I-Beam will be entered into the annual SAMPE 2012 competition to compete against other schools and universities nationwide. These I-Beams will undergo a three point bending test, and must withstand the greatest load whilst remaining in the parameters set by SAMPE. This I-Beam will go on to take third place internationally. In addition, the …

Flaperon Assembly Manual For Pegastol Aftermarket Wings, Eric Alan Gray

Aerospace Engineering

No abstract provided.

Human Powered Helicopter: Rotor Structure, Joseph Ram, Juan Carlos Olvera

Mechanical Engineering

The following report encompasses the Human Powered Helicopter Rotor Team’s conceptual models and ideas based on research and modeling analysis. The following gives an overview of material researched, concept generation, analyzation, manufacturing, and testing for a rotor structure to be installed in a Human Powered Helicopter.

Development Of A Ground Based Atomic Oxygen And Vacuum Ultraviolet Radiation Simulation Apparatus, Max Jay Glicklin

Master's Theses

The space environment possesses numerous unique and unusual attributes, creating challenges that must be considered in order to accomplish a successful space mission. Two of the detrimental aspects of the space environment include Atomic Oxygen, AO, and Ultraviolet, UV, radiation. UV radiation becomes more severe in space as there is no atmosphere to attenuate incoming photons, thereby exposing spacecraft to radiation that never reaches the surface of the Earth. Overall, space vehicles are exposed to a total of 107.4 Watts/m² of light shorter than 400 nm. AO is created by the photo disassociation of molecular oxygen by UV radiation …

Design Of A Human Powered Helicopter Airframe, Sheen Kao, Daniel Layton, Philip Sobol

Mechanical Engineering

In 1989 Cal Poly’s Da Vinci III was the first human powered helicopter (HPH) to achieve flight; our goal is to research and develop a new airframe for the next generation Da Vinci. This report outlines a brief history of human powered flight and details a method of constructing for the airframe. An optimized airframe geometry was also researched and is explained in detail.

An Experimental Investigation Of Glare And Restructured Fiber Metal Laminates, Adelina Vanessa Benedict

Doctoral Dissertations and Master's Theses

Fiber Metal Laminates (FMLs) are a group of materials fabricated by bonding glass/epoxy layers within metal layers. This class of materials can provide good mechanical properties, as well as weight savings. An FML known as Glass Laminate Aluminum Reinforced Epoxy (GLARE) was studied. An experimental investigation comprising of microscopy and tensile testing was carried out using different grades of GLARE. Microscopy revealed the construction details of GLARE, while tensile testing provided means of measuring and analyzing its stress-strain responses. Next, different metal surface pretreatment methods were explored. These included sandblasting, Phosphoric Acid Anodizing (PAA), and AC-130 Sol-Gel treatment. Woven S-2 …

Feasibility Study Into The Use Of 3d Printed Materials In Cubesat Flight Missions, Daniel Fluitt

Master's Theses

The CubeSat Program has provided access to space for many universities, private companies, and government institutions primarily due to the low cost of CubeSat satellite development. While these costs are orders of magnitude lower than similarly capable nano-satellite missions, they are still outside of the budgetary constraints of many potential developers including university and high school clubs. Using 3D printed plastics in the production of CubeSat structures and mechanisms presents a large cost savings opportunity that will allow these institutions to participate in the development of these satellites, expanding the educational and scientific impact of the CubeSat Program.

Five rapid …

Modal Analysis Of Composite Structures With Damping Material, Kellie Michelle Tremaine

Master's Theses

The purpose of this study is to develop an analytical solution for modal analysis of actively damped orthotropic composite plates in bending and to verify it with experimental analysis.

The analytical modal analysis solution for composite plate dynamics is derived using Euler theory. This analysis applies to structures with orthotropic lamina of uniform material properties at any lamination angle. The bending-extensional coupling can be neglected for plates that are symmetric or approximately symmetric, which allows an exact solution for natural frequency and mode shape to be obtained. An exact solution can be found for natural vibration and in general.

The …