Aerospace Engineering Commons^™

Mechanism Of Compaction With Wrinkle Formation During Automatic Stitching Of Dry Fabrics And The Size Effect Of Compression Molded Discontinuous Fiber-Reinforced Composites, Anibal Benjamin Beltran Laredo

Mechanical & Aerospace Engineering Theses & Dissertations

With an ever-increasing demand for composites, more ways of manufacturing them are becoming popular and widely used. Stitching of dry fabrics is an efficient method for improving delamination resistance. Discontinuous fiber reinforced composites can be used as a lightweight alternative material for metals through a process of compression molding, which allows for complex shape manufacturing while offering structural grade mechanical properties.

This study demonstrates how the stitching of dry fabrics can be adapted to more complex surfaces. The consequences of stitching of curvilinear surfaces can result in defect formation. Therefore, to understand the physical formation of possible defects, experimental characterization …

Topology Optimization And Analysis Of Thermal And Mechanical Metamaterials, Lee Alacoque

Doctoral Dissertations and Master's Theses

To take advantage of multi-material additive manufacturing technology using mixtures of metal alloys, a topology optimization framework is developed to synthesize high-strength spatially periodic metamaterials possessing unique thermoelastic properties. A thermal and mechanical stress analysis formulation based on homogenization theory is developed and is used in a regional scaled aggregation stress constraint method, and a method of worst-case stress minimization is also included to efficiently address load uncertainty. It is shown that the two stress-based techniques lead to thermal expansion properties that are highly sensitive to small changes in material distribution and composition. To resolve this issue, a uniform manufacturing …

Through-Thickness Reinforcement And Repair Of Carbon Fiber Based Honeycomb Structures Under Flexure And Tension Of Adhesively Bonded Joints, Aleric Alden Sanders

Mechanical & Aerospace Engineering Theses & Dissertations

Repair and reinforcement of composite honeycomb structures is an area of concern as higher demands are being placed on high strength, lightweight structural materials, such as carbon fiber reinforced plastics and corresponding honeycomb structures. A common issue with these structures is when a delamination in the facesheet may form and spread, leading to a failure scenario. An investigation of adding a through thickness reinforcement (TTR) to these structures at the sample level that undergo four-point-bending, tension, and joining methods is conducted throughout this thesis. The embedding of pultruded carbon fiber rods is found to be an ideal addition to composite …

Peridynamic Approaches For Damage Prediction In Carbon Fiber And Carbon Nanotube Yarn Reinforced Polymer Composites, Forrest E. Baber

Theses and Dissertations

Aerospace structures are increasingly utilizing advanced composites because of their high specific modulus and specific strength. While the introduction of these material systems can dramatically decrease weight, they pose unique certification challenges, often requiring extensive experimental testing in each stage of the design cycle. The expensive and time-consuming nature of experimental testing necessitates the advancement of simulation methodologies to both aid in the certification process and assist in the exploration of the microstructure design space.

Peridynamic (PD) theory, originating from Sandia National Lab’s in the early 2000’s, is a nonlocal continuum-based method that reformulates the equation of motion into an …

Assessment Of Material State In Composites Using Global Dielectric State Variable, Vamsee Vadlamundi

Mechanical and Aerospace Engineering Dissertations - Archive

Composites are heterogeneous in nature and a fundamental understanding of the material response to applied mechanical, thermal, electrical and other multi-physical fields is required to efficiently design and synthesize the material system and demands attention to long-term behavior in particular. Unlike metals, composites are designed to develop distributed damage and initiation of a single microscopic crack does not individually affect the strength/life of these materials. Therefore, the primary interest is not in single local events but in the process of interaction of multiple events that have a collective global effect on the material behavior. The interaction of these local events …

Hybrid Structural Composites With Energy Harvesting Capabilities, Simon Furnes

Doctoral Dissertations and Master's Theses

Hybrid materials have received significant interest due to the potential enhancements they provide over traditional materials such as sensing, actuating, energy scavenging, thermal management, and vibration damping. While traditional materials can be utilized for either one of these functions or loadbearing, the hybrid materials are superior as they allow combination of a wide array of functionalities whilst being suitable for load-bearing purposes.

The goal of this thesis is to elucidate the synergistic effects of hybridization of two piezoelectric materials; zinc oxide nanowires (ZnO NWs) and thin film of lead zirconium titanate (PZT) on the mechanical and energy harvesting of beams …

Characterization Of 3d Printed Pla With The Help Of Mechanical, Di-Electric And X-Ray Diffraction Techniques, Sai Sri Nidhi Munaganuru

Mechanical and Aerospace Engineering Theses - Archive

Additive manufacturing (AM) revolutionized many industries, i.e., Automotive, Biomedical, Aerospace and Defense. As opposed to traditional manufacturing methods, a part is manufactured layer by layer from 3D CAD models in AM. Though the vision of AM is impressive, there are many challenges that are hindering the widespread use of these complex parts. One of the main challenges is its strength that varies with different manufacturing parameters. We are going to investigate the effect of build parameters on the mechanical, electrical and crystalline properties of the additively manufactured heterogeneous material system. The goal of the thesis is to find a correlation …

Fluorine-Containing Oxidizers For Metal Fuels In Energetic Formulations, Siva Kumar Valluri, Mirko Schoenitz, Edward Dreizin

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Fluorine containing oxidizers, primarily polymers, are extensively used in pyrotechnic compositions. Fluorinated oxidizers are less explored for metalized propellants and explosives despite a potential advantage of substantial heat release combined with gaseous combustion products. This review summarizes different types of fluorinated oxidizers used in energetic formulations or of potential interest for such systems, including gases, polymers, and inorganic compounds. Types of energetic formulations employing metals and fluoropolymers are discussed in more detail, including methods used to prepare composites and resulting salient features of the obtained materials. Laboratory experiments characterizing such materials, in particular, electron microscopy and thermal analysis, are discussed, …

Investigation On Effective Modulus And Stress Concentration Factor Of 3d Reinforced Composite By Finite Element Analysis Method, Chandra Bhaskar Reddy Pittu

Mechanical and Aerospace Engineering Theses - Archive

Micromechanics of Composites aims to analyze the localized stresses inside any given constituents of the composite structure. This Thesis is focused on Calculating the effective modulus and the Stress concentration factor of the 3D straight Fiber Composite using Finite Element(FE). The compressive and a Shear response of a 3D Straight fiber composite comprising three directional E Glass Fibers reinforced in an epoxy matrix is analysed. This result is the 10% of overall Composite Ductility and a 10% of overall Shear displacement load in the orthogonal directions. FE calculations are reported to analyse the response of 3d reinforcement as of with …

Finite Element Analysis Of Composite Reactor Pressure Vessel, Tejas Vasant Mhetre

Mechanical and Aerospace Engineering Theses - Archive

Reactor Pressure Vessel is the container designed to hold gases or liquids above atmospheric pressure. The focus of this study is to develop Finite Element Model to predict the performance of composite reactor pressure vessel subjected to extreme pressure and temperature and compare with pressure vessel manufactured using conventional materials. In the first part of the study, a pressure vessel system with Carbon steel material under design pressure and temperature have been analyzed for stresses, deformation and Safety Factor. Various loading cases have been discussed during the analysis of pressure vessel. Composite materials have been a suitable replacement to the …

Finite Element Analysis And Design Improvement Of Aerospace Composite Hinges, Gaurang Girish Sonpal

Mechanical and Aerospace Engineering Theses - Archive

Hinges are the most commonly used mechanical bearings to connect 2 objects for relative rotational motion. Modern day aerospace hinges are generally made using either Aluminum, Steel or bronze. The study analyzes the use of composite material as an alternative to traditional materials for manufacturing these hinges. The research is focused on the Finite element Analysis of a composite hinge as well as an aluminum hinge. The load capacity of both the types of hinges are compared. To improve the design of the composite hinge, a combination of composite material and aluminum is used to model a hybrid hinge design. …

Comparison Of Cross-Sectional Profiles For Side Impact Crash Structure In Passenger Vehicle, Nitish Sharma

Mechanical and Aerospace Engineering Theses - Archive

Car’s safety is most important structural criteria while designing an automotive chassis. To protect the occupants from a direct impact, the passenger cabin and the structure of the vehicle should have an appropriate stiffness so that the it absorbs any kind of impact and keeps the passenger safe. Design standards are set by various vehicle safety association around the world based on different crash situations i.e. front crash, side impact, roll over etc. Among these standards, side impact crash account for over all 40% crashes all around the world and is one of the most fatal crash scenarios. This research …

Fea Of Carbon Composite As A Substitute For Steel (A992) In Case Of Square Or Rectangular Hollow Cross-Sections As Beams And Columns, Pradeep Ganesh Pai

Mechanical and Aerospace Engineering Theses - Archive

Improvement to an existing design is an ongoing and never-ending process in every field. The improvement can be in a myriad of areas like an increase in strength, reduction in weight, stiffness to a loading condition and so on. The way it is achieved can range from changing the properties of the material used by incorporating various manufacturing processes or by using an alternative material which can sustain the same loading conditions or for that matter, work better than the existing material. Composite materials like Carbon Fiber, Glass Fiber or Kevlar Fiber reinforced plastics, to name few, are being used …

Human-Robot Collaborative Force-Controlled Micro-Drilling For Advanced Manufacturing And Medical Applications, Parimal Mahesh Prajapati

Mechanical & Aerospace Engineering Theses & Dissertations

Robotic drilling finds applications in diverse fields ranging from advanced manufacturing to the medical industry. Recent advances in low-cost, and human-safe, collaborative robots (e.g., Sawyer) are enabling us to rethink the possibilities in which robots can be deployed for such tedious and time-consuming tasks. This thesis presents a robotic drilling methodology with features of force-control enabled micro-drilling and human-robot collaboration to reduce programming efforts and enhance drilling performance. A Sawyer robot from Rethink Robotics, which offers safe physical interactions with a human co-worker, kinesthetic teaching, and force control, is used as the test bed. The robot’s end-effector was equipped with …

A Micromechnics Approach To Predicting The Onset Yielding Envelope Of Particulate Composite Materials, Behrooz Karimi

Mechanical and Aerospace Engineering Dissertations - Archive

Composite materials fail for various reasons and extensive research has been conducted both experimentally and theoretically. However, theoretical prediction of composite failure by yielding seems scarce. Adding reinforcing elements to matrix significantly affects the structural behavior of composite materials. The inserted particles on one hand obstruct the progress of cracks and on the other hand cause stress concentration on the interface of the particle-matrix and eventually influence the ultimate strength of the material. In this research, we study the interface stresses and strength in particulate reinforced composites under uniform mechanical and thermal loading. We theoretically obtain failure envelopes for particulate …

Investigation On Metal-Composite Hybrid Flywheels Using Finite Element Method, Ching Huai Wang

Mechanical and Aerospace Engineering Theses - Archive

This research is aimed to investigate the kinetic energy storage of a hybrid metal-composite flywheel rotating at high speeds. The upper limit of energy, which flywheel can supply, is restricted by the strength of material because both energy and stress are proportional to the density of the material and the square of the velocity. Metal flywheels operate at lower rotational speed and supply less energy than the composite flywheels. Composite flywheels have a very high density per unit mass, but lower energy density per unit of the design volume. The ultra-high speed of composite flywheels creates some engineering challenges such …

Strength And Damage Prognosis Of Adhesive Bond And Inter-Ply Hybrid Composites Based On Dielectric Properties, Priyanshu K. Banerjee

Mechanical and Aerospace Engineering Theses - Archive

Composite materials have found their applications in a wide range of industries particularly in the aerospace and automotive sectors. This is because they are comparatively light-weight and provide a much better corrosion and wear resistance as compared to other ceramics and metals. Adhesive bonding can be used to improve the stress distribution between these composite materials. Moreover, adhesive bond decreases the weight and concentration of stresses in the structure. Broadband Dielectric Spectroscopy, BbDS is a robust tool used for analyzing the dielectric properties of a polymer composite. This method can be used to monitor the curing process of the specimen. …

A Comparison Study Of Composite Laminated Plates With Holes Under Tension, Joun S. Kim

Master's Theses

A Comparison Study of Composite Laminated Plates with Holes under Tension

A study was conducted to quantify the accuracy of numerical approximations to deem sufficiency in validating structural composite design, thus minimizing, or even eliminating the need for experimental test. Error values for stress and strain were compared between Finite Element Analysis (FEA) and analytical (Classical Laminated Plate Theory), and FEA and experimental tensile test for two composite plate designs under tension: a cross-ply composite plate design of [(0/90)4]s, and a quasi-isotropic layup design of [02/+45/-45/902]s, each with a single, centered hole of 1/8” diameter, and 1/4" diameter (four sets …

Advanced Methods Of Nondestructive Inspection Of Composite Structures Based On Limited Angle X-Ray Computed Tomography, Ekaterina Bostaph

Mechanical and Aerospace Engineering Dissertations - Archive

This research aimed to study the potential for breaking through object size limitations of current X-ray computed tomography (CT) systems by implementing a limited angle scanning technique. CT stands out among other industrial nondestructive inspection (NDI) methods due to its unique ability to perform 3D volumetric inspection, unmatched micro-focus resolution, and objectivity that allows for automated result interpretation. This work attempts to advance NDI technique to enable microstructural material characterization and structural diagnostics of composite structures, where object sizes often prohibit the application of full 360o CT. Even in situations where the objects can be accommodated within existing micro-CT configuration, …

Analysis Of Composite Structures With Curvature Under Temperature Environment, Muthu Ram Prabhu Elenchezhian

Mechanical and Aerospace Engineering Theses - Archive

Composite structures are frequently exposed to environments with change in temperatures during their service life. The thermal behaviours of the laminated composite structures are more pronounced than that of the structures made of isotropic materials. For the structures under thermal environment, extensive studies have been conducted to investigate the induced thermal stresses and deformation of composite laminated plates by linear/non-linear analysis and composite structures by finite element analysis. The main focus of this study is concentrated on development of an analytical method for analyzing composite thin shells and/or moderate curved beam structures under temperature environment. This includes the derivation of …

Load Carrying Capacity Management Of Compound Anisotropic Composite Rings Under External Pressure, Salman Bakhrayba

Mechanical and Aerospace Engineering Theses - Archive

Composites have much higher strength than conventional materials such as steel. This makes it attractive to replace heavy loaded structural elements, made traditionally from steel, by elements made from composites. However, it is not a trivial task for statically indeterminate structures due to anisotropy of elastic and strength properties of composites. Present investigation is done for a ring subjected to external load. Such rings are used as bulkheads in many applications. Dependence of ultimate external pressure on thickness of the ring is nonlinear one. It is related to non-uniformity of distribution of circumferential stresses, with anisotropy of material, with set …

Finite Element Analysis Of Composite Aircraft Fuselage Frame, Aditya Milind Dandekar

Mechanical and Aerospace Engineering Theses - Archive

Composites have been introduced in aircraft industries, for their stronger, stiffer, and lighter properties than their metal-alloys counterparts. The general purpose of an aircraft is to transport commercial or military payload. Aircraft frames primarily maintains the shape of fuselage and prevent instability of the structure. Fuselage is similar as wing in construction which consist of longitudinal elements (longerons and stringers), transverse elements (frames and bulkheads) and its external skin. The fuselage is subjected to forces such as the wing reactions, landing gear reaction, empennage reaction, inertia forces subjected due to size and weight, internal pressure forces due to high altitude. …

The Effect Of Biocomposite Material In A Composite Structure Under Compression Loading, Benjamin Andrew Sweeney

Master's Theses

While composite structures exhibit exceptional strength and weight saving possibilities for engineering applications, sometimes their overall cost and/or material performance can limit their usage when compared to conventional structural materials. Meanwhile ‘biocomposites’, composite structures consisting of natural fibers (i.e. bamboo fibers), display higher cost efficiency and unique structural benefits such as ‘sustainability’. This analysis will determine if the integration of these two different types of composites are beneficial to the overall structure. Specifically, the structure will consist of a one internal bamboo veneer biocomposite ply; and two external carbon fiber weave composite plies surrounding the bamboo biocomposite. To acquire results …

Wrinkling Of Functionally Graded Sandwich Structures Subject To Biaxial And In-Plane Shear Loads, Harold Costa

Masters Theses

"Benefits of a functionally graded core increasing wrinkling stability of sandwich panels have been demonstrated in a recent paper [1] where a several-fold increase in the wrinkling stress was observed, without a significant weight penalty, using a stiffer core adjacent to the facings. In the present paper wrinkling is analyzed in case where the facings are subject to biaxial compression and/or in-plane shear loading and the core is arbitrary graded through-the-thickness. Two issues addressed are the effect of biaxial or in-plane shear loads on wrinkling stability of panels with both graded and ungraded core and the verification that functional grading …

Static And Dynamic Fea Analysis Of A Composite Leaf Spring, Himanshu Arun Raut

Mechanical and Aerospace Engineering Theses - Archive

Composite materials are widely used in aeronautical, marine and automotive industries, because of their excellent mechanical properties, low density and ease of manufacture. Due to this increasing trend to utilize composite materials, it has become necessary to investigate the pros and cons of composites. This research investigated the static and dynamic behaviors for a composite leaf spring that are used in Chevrolet Corvette Grand and light tractor-trailers. The objective of this study was to find the cause of de-lamination/ failure of the unidirectional composite layers in varying cross sections of the leaf spring. Finite element method is used to calculate …

Thermal Stress Analysis Of Unidirectional Composite Material By Fem Modeling, Gopal D. Gulwani

Mechanical and Aerospace Engineering Theses - Archive

Micromechanics of composite is study of complex mechanism of stress and strain transfer between fiber and matrix within a composite as well as distributions of physical fields inside heterogeneous medium. It was used successfully in predicting accurately physical properties like effective stiffness, effective linear thermal expansion of heterogeneous materials like composite. However, when it comes to strength characteristics of composite especially in transversal direction it failed to predict more accurate results. This thesis is focused on thermally induced stress analysis of unidirectional composite by finite element method. Thermal stresses which are dangerously ignored factor in mechanics of composite usually occur …

Effect Of Structural Variations On Thermal Deformation Of Single Curvature Composite Sandwich Panels, Brady C. Lotz

Mechanical and Aerospace Engineering Theses - Archive

Composite structures cured at a high temperature in a contoured female mold have a tendency to deform or spring-in when brought down to room temperature from cure temperature. This thesis investigates the effects of various structural parameters on the spring-in of the curved shape of a composite sandwich panel due to thermal deformation. A finite element model of a single curved composite sandwich panel is developed using 3D shell elements and validated against other published articles and classical lamination theory. Using a control structure of AS4/3501-6 carbon/epoxy with half inch Nomex honeycomb core with a layup of [0°/90°/0°/90°/Core/90°/0°/90°/0°]T, structural parameters …

Vibration Analysis Of A Composite Wing Box With Arbitrarily Shaped Spars And Ribs, Rossana R. Fernandes

Doctoral Dissertations and Master's Theses

In this research, the free vibration analysis of composite wing boxes with curvilinear spars and ribs is performed. Modern manufacturing technologies, such as Electron Beam Freeform Fabrication and Friction Stir Welding, have allowed the manufacturing of arbitrarily shaped stiffeners. Curvilinear stiffeners provide flexibility in design as they can assume an infinite number of paths. Curvilinear spars and ribs can in some instances provide a better vibration and static response than their straight counterparts while reducing the overall mass of the structure. An equivalent continuum plate model of a wing box using energy formulations is proposed at the preliminary design stage …

Effect Of Low Velocity Impact On The Vibrational Behavior Of A Composite Wing, Richard M. De Luna

Master's Theses

Impact strength is one of the most important structural properties for a designer to consider, but it is often the most difficult to quantify or measure. A major concern for composite structures in the field is the effect of foreign objects striking composites because the damage is often undetectable by visual inspection. The objective for this study was to determine the effectiveness of using dynamic testing to identify the existence of damage in a small scale composite wing design. Four different impact locations were tested with three specimens per location for a total of 12 wings manufactured. The different impact …

Dynamic Transverse Debondong Of A Single S-2 Fiber, Stephen E. Levine

Open Access Theses

Fiber reinforced composites are becoming increasingly common due to their high strength to weight ratios as compared to more conventional materials. Along with this increased used comes the need to have a higher level of understanding of the material characteristics. Specifically, the interface between the fiber and matrix is of particular interest. Loss of adhesion at this interface, known as debonding, can greatly decrease material strength. There has been significant research into debdonding phenomena at low strain rates. However, there is still a need for further insight at higher strain rates. In addition, given the opacity of many epoxy resins, …