Mechanical Engineering Commons^™

Low-Cost Strider For Guatemala, Nicole Catherine Cooper, Gonzalo Hernandez, Jared W. Tower

Mechanical Engineering

The purpose of this project was to create a strider, a type of standing rehabilitation device, for children in developing countries who have trouble walking and supporting their full body weight. The project was initially brought to us by Cal Poly professor Brian Self, who had visited a clinic in San Marcos and determined that there were children there who had difficulties with walking and were a need for a rehabilitation device. The team discussed the problem with Dr. Self, Matt Robinson (a local San Luis Obispo prosthetist), and Cal Poly physics professor Pete Schwartz, all of whom had visited …

Development Of A Finite Element Model For Predicting The Impact Energy Absorbing Performance Of A Composite Structure, Matthew Lowell Roberts

Master's Theses

Because of their high strength-to-weight ratio, Fiber Reinforced Composite (FRC) materials are well suited for use in high performance racing applications where weight must be kept to a minimum. Formula SAE (FSAE) race cars are designed and built by college students, roughly following the model of a scaled down Formula One car. Strict regulations are placed on specific components of the car in the interest of equalizing competition and ensuring the safety of the drivers. Students are required to construct a survival cell (the chassis), which can resist large amounts of energy in the event of a crash, with an …

Design Optimization Of A Composite Wing Box For High-Altitude Long-Endurance Aircraft, Philip T. Arévalo

Doctoral Dissertations and Master's Theses

A design optimization process is developed to define the wing box structure for High-Altitude Long-Endurance Aircraft (HALE). The goal of this study is to determine the best tradeoff between mass and rigidity of a HALE aircraft wing structure. A preliminary composite laminate structural design procedure is described which uses a NASTRAN-based Finite Element Analysis (FEA), and the Hierarchical Evolutionary Engineering Design System (HEEDS) MDO software to define a locus of acceptable, optimized wing box design definitions.

Comparison Of Manufacturing Techniques For Composites Subjected To High Speed Impact, Kenneth Gollins

Dissertations and Theses

No abstract provided.

Fabrication Of Out-Of-Autoclave Bismaleimide Based Composite Laminates With Embedded Fiber Optic Sensors, Sudharshan Anandan

Masters Theses

"Composites are becoming the material of choice in applications where weight savings are critical, like aerospace structures. The common composites used are- Carbon/Epoxy and Carbon/Bismaleimide (BMI). BMI based systems are preferred in applications which involve operating temperatures higher than conventional epoxies. Carbon/BMI laminates are traditionally fabricated in an autoclave, which is associated with high operating costs. In this work, a low cost out of autoclave (OOA) process is evaluated. It is desirable to have BMI OOA prepreg systems cure at reasonably low temperatures with sufficient degree of cure and green strength to maintain rigidity for subsequent freestanding post cure Carbon/BMI …

Performance Evaluation Of Polyurethane Composites Using Vacuum Infusion Process, Mohaned M. Mohamed

Doctoral Dissertations

"Glass fiber-reinforced polymer composites have promising applications in infrastructures due to their low cost, high specific stiffness/strength, and corrosion resistance. The pultrusion process is often used to manufacture glass fiber-reinforced polyurethane (PU) composite. The objective of this study is to use thermoset PU resin to manufacture high quality composites for infrastructure applications using vacuum assisted resin transfer molding (VARTM) process. Using VARTM to fabricate PU resins presents unique challenges. Several modifications however have helped with overcoming these problems. In part I of the research, the mechanical performance of two different PU resin not only evaluated but also compared to one …

Surface Treatment Of Fly Ash For Improving The Tensile Strength Of Fly Ash/Unsaturated Polyester Composites, Sugiman Sugiman, Paryanto Dwi Setyawan

Makara Journal of Technology

The paper presents the surface treatment of fly ashes using acid and alkali solution on the tensile strength of the fly ash/unsaturated polyester (UP) composites. Sulfuric acid (H2SO4), hydrofluoric acid (HF) and sodium hydroxide (NaOH) solution with concentration of 0%, 5%, 10%, 15%, and 20% (by weight) were used for surface treatment of fly ashes. Generally, the tensile strength of the treated fly-ash/UP composites shows a significant increase compared to the untreated fly ash. Of all surface treatments studied, the optimum tensile strength was obtained at a concentration of 10%. At this concentration, at a fly ash content of 30% …

Thermal Analysis Of Carbon Nanofiber Reinforced Isotactic Polypropylene, Anna Alicia Hernandez

Theses and Dissertations - UTB/UTPA

Isotactic Polypropylene (IPP) is a commonly known thermoplastic that has unique properties include being light weight, high performance, impact strength, tensile strength, elongation, and high temperature properties. The use of vapor grown carbon nanofiber (VGCNF) reinforcements on polypropylene has shown to produce high specific modulus, strength, electrical and thermal properties on specimens. Thermogravimetric (TGA) investigations on the thermal degradation of isotactic polypropylene – vapor grown carbon nanofibers composites in nitrogen were reported. The mass evolution as a function of temperature is a single sigmoid for both polypropylene and polypropylene loaded with VGCNF. The inflection temperature of these sigmoids increases as …

Experimental And Finite Element Studies Of Shock Transmission, Eldon Jerry Goddard

UNLV Theses, Dissertations, Professional Papers, and Capstones

Composite materials are more widely used today in engineering products than ever before. Shock transmission in jointed composite sections needs to be investigated to understand the affect of composite materials on the dynamic response of the system. There exists limited published work on transient shock propagation through composite sections. The aim of this study is to analyze the transient behavior of joints in composite materials subjected to low impact loads and to develop a computational model that provides an improved physics based shock model. The jointed connection will be investigated experimentally and using Finite Element Analysis (FEA). The bolted joint …

Drape Forming Machine, Adam Johnson, Will Schlosser, Brian Miller

Mechanical Engineering

The goal of this project was to build a prototype machine that formed multiple sheets of debulked pre-preg OOA carbon fiber into a 2-foot long trapezoidal shape. The machine was required to do this process semi-automatically.

Low Strain Rate Studies Of Alumina Epoxy Composites Using Piezospectroscopy, Ashley Jones

Electronic Theses and Dissertations

Particulate composites are widely used in many aerospace and military applications as energetic materials, armor materials or coatings and their behavior under dynamic loads have gained increasing significance. The addition of modifiers such as alumina nanoparticles generally facilitates the improvement of the mechanical strength to density ratio due to high specific area and particle rigidity. This allows for sufficient particlematrix bonding and therefore improved stiffness and load transfer in the composite. Photo-luminescent α-alumina nanoparticles when embedded in an epoxy matrix allow for the added benefit of in situ measurements at low strain rates to provide stress-sensitive information using the particle …

Nano-Particles In Multi-Scale Composites And Ballistic Applications, Jason Gibson

Electronic Theses and Dissertations

Carbon nanotubes, graphene and nano sized core shell rubber particles have all been extensively researched for their capability to improve mechanical properties of thermoset resins. However, there has been a lack of research on their evaluation for energy absorption in high velocity impact scenarios, and the fundamental mechanics of their failure mechanisms during highly dynamic stress transfer through the matrix. This fundamental research is essential for laying the foundation for improvement in ballistic performance in composite armor. In hard armor applications, energy absorption is largely accomplished through delamination between plies of the composite laminate. This energy absorption is accomplished through …

Wolfpack Gear Inc. Composite Frame Firefighter Backpack, Gabriel Mountjoy, Blair Ridings, Carl Drummond Buchenroth

Mechanical Engineering

No abstract provided.

Finite Element Modeling Of Ballistic Impact On A Glass Fiber Composite Armor, Dan M. Davis

Master's Theses

Finite Element Modeling of Ballistic Impact on a Glass Fiber Composite Armor

Dan Davis

Experiments measuring the ballistic performance of a commercially available fiberglass armor plate were used to guide the development of constitutive laws for a finite element model of the impact. The test samples are commercially available armor panels, made from E-glass fiber reinforced polyester rated to NIJ level III. Quasi-static tensile tests were used to establish material properties of the test panels. These properties were then used to create models in the explicit finite element code LSDYNA.

Ballistic impact testing of the panels was conducted using a …

Method For The Simulated Layup Of Composite Fabrics, David M. Christensen

Theses and Dissertations

Due to the complexity of designing advanced composite parts, many software tools have been developed to aid the designer and reduce design cycle time. Draping is one of those tools and is used to predict the fiber angles throughout the part. This application of draping is to simulate the actual hand layup process that a technician would go through while creating a multi-layered laminate composite part. This method is the first to use plies as an underlying surface for draping instead of just using an offset mold surface. This method can visualize full 3D ply geometry taking into account the …

Feasibility Analysis For Electrically-Powered Hoverboard, Cameron Chan, Jason Cortez, Jay Lopez

Aerospace Engineering

Composite materials are engineered by combining two or more constituent materials with significantly different physical or chemical properties in such a way that the constituents are still distinguishable, and not fully blended. Due to today’s high rising prices of gasoline and aviation fuel costs, many manufacturers have turned to the use of lightweight composites in their designs due to the advantages of the composite material, which include outstanding strength, excellent durability, high heat resistance, and significant weight reduction that the composite material properties hold. The purpose of this project is to design and construct a composite structure for an electrically-powered …

Advanced Ceramics And Composites Based On Rice Hulls, Peigen Zhang

LSU Doctoral Dissertations

As a by-product of the agricultural industry, rice hulls are available at large volume across the world. The disposal of the rice hulls itself is a big problem for the rice millers where the rice paddies are peeled off and rice hulls are produced. There have been many disposal methods developed, but the true value of the rice hulls would be more appreciated when they are employed to produce high value-added advanced ceramics. In this dissertation, advanced ceramics, such as AlN nanowires, SiC whiskers, mullite and SiC/Al2O3 nano-sized composites, were developed and studied based on the rice hulls. The SiC …

Embedded Piezoelectric Fiber Composite Sensors For Applications In Composite Structures, Hari Prasad Konka

LSU Doctoral Dissertations

Health monitoring of the composite structures is an important issue that must be addressed. Embedded sensors could be an effective way to monitor the health of composite structures continuously and which could also avoid the catastrophic failures of composite structures. Piezoelectric-fiber-composite sensors (PFCS) made from micro-sized Lead Zirconate Titanate (PZT) fibers have great advantages over the traditional bulk PZT sensors for embedded sensor applications. PFCS as an embedded sensor will be an ideal choice to continuously monitor the stress/strain levels and health conditions of composites. This work presents a critical study on using PFCS as an effective embedded sensor within …

Axisymmetric Finite Element Modeling For The Design And Analysis Of Cylindrical Adhesive Joints Based On Dimensional Stability, Paul E. Lyon

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The use and implementation of adhesive joints for space structures is necessary for incorporating fiber-reinforced composite materials. Correct modeling and design of cylindrical adhesive joints can increase the dimensional stability of space structures. The few analytical models for cylindrical adhesive joints do not fully describe the displacement or stress field of the joint.

A two-dimensional axisymmetric finite element model for the design and analysis of adhesive joints was developed. The model was developed solely for the analysis of cylindrical adhesive joints, but the energy techniques used to develop the model can be applied to other types of joints as well. …

Fabrication Of Multi-Material Structures Using Ultrasonic Consolidation And Laser-Engineered Net Shaping, John Olorunshola Obielodan

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This research explores the use of two additive manufacturing processes for the fabrication of multi-material structures. Ultrasonic consolidation (UC) and laser- engineered net shaping (LENS) processes were used for parallel systematic investigations of the process parameters and methodologies for the development of multi-material structures.

The UC process uses ultrasonic energy at low temperature to bond metallic foils. A wide range of metallic materials including nickel; titanium; copper; molybdenum; tantalum; MetPreg®; silver; stainless steel; and aluminum alloys 1100, 3003, and 6061 were bonded in different combinations. Material domains are inherently discrete in ultrasonically consolidated structures. The mechanical properties of some of …

Modeling And Simulation For Shape Memory Polymer Based Self-Healing Syntactic Foam, Wei Xu

LSU Doctoral Dissertations

Syntactic foams, renowned for their low density and high mechanical properties, are enjoying continuing growth in various civilian and military sectors. However, like laminated composites, foam cored structures are vulnerable to impact damages and suffering from inabilities in repairing macro-scale cracks. A self-healing mechanism for structural damage is genuinely desired. A recent development in self-healing structural damage is a two-step close then heal (CTH) scheme proposed by Li and Nettles [1] and elucidated by Li and Uppu [2], by mimicking the self-healing process of human skin. This concept has been further demonstrated in Nji and Li’s work [3] that a …

Carbon Fiber Leaf Springs For Adaptive Cross Country Skiing, William Drew Atkinson

Master's Theses

This work describes the development of a custom sit ski for US Ski Team paralympian Greg Mallory from concept through prototype fabrication. The ski consists of a custom seat molded specifically for the athlete, carbon fiber leaf springs, and a custom binding attachment system compatible with NNN style cross country bindings. The sit ski is designed to maximize poling power through the use of an upright rather than reclined seating position, allowing for increased utilization of core muscle strength. The springs were designed based on information gathered by a custom National Instruments data acquisition system, and stiffness analysis was conducted …

Manufacture, Characterization, And Application Of Multiwall Carbon Nanotube Composite Crylonitrile-Butadiene-Styrene, Daniel Ray Bortz

University of Kentucky Master's Theses

Carbon nanotubes have been studied for nearly two decades and their amazing properties continue to spur intense investigation in the area of polymer composites. In terms of potential commercialization, mutiwall carbon nanotubes (MWCNTs) are currently the most prevalent and economically viable form of nanotubes. Uncovering innovative means to take full advantage of their properties remains a fundamental issue. In this thesis, viability of their use to reinforce polymeric systems is reported. Acrylonitrilebutadiene- styrene (ABS) was used as the host matrix. MWCNTs were introduced to the ABS matrix via melt compounding. The resulting composite was thoroughly rheologically, thermally, and mechanically characterized. …

A Method For Winding Advanced Composites Of Unconventional Shapes Using Continuous And Aligned Fibers, Abraham K. Allen

Theses and Dissertations

Advanced composites are extremely strong, rigid, and light, even when compared with advanced metals. Advanced composites are replacing high-tech metals as the material of choice for aerospace engineering. However, the processes used to manufacture advanced composites generally lose some of the properties of the materials by their process limitations.

One process that keeps the theoretically awesome qualities of the composite materials in tact is filament winding. Filament wound parts are used as rocket shells, bicycle frame tubes, drive shafts, pressure vessels, etc. Filament winding is an automated process and makes reliable parts to close tolerances. If a straight tube were …

Analysis Of Microdamage Evolution Histories In Composites, Yuris A. Dzenis, Jie Qian

Department of Engineering Mechanics: Faculty Publications

Evolution of microdamage in advanced composites was experimentally studied in this paper. A new method of acoustic emission (AE) analysis of histories of different damage mechanisms was formulated based on a combination of transient AE classification and multiparameter filtering. The capabilities of the method were illustrated on examples of damage evolution in several graphite/epoxy composites. Three characteristic AE waveforms with different frequency spectra were identified based on the transient analysis. Regions occupied by these waveforms in the amplitude–rise time parametric space were identified for the [0]₈ and [90]₁₆ unidirectional composites. Multiparameter filtering was applied to extract evolution histories …

Development Of Strength Theories For Random Fiber Composites, Victor Giurgiutiu

Faculty Publications

A ressessment of existing theories for calculating the strength of random and quasi-random fiber composites is presented. Fundamental aspects regarding the physical model, macromechanics analysis, fiber distribution functions, generalized failure criterion, and progressive versus sudden failure models are covered first. Progressive ductile failure, progressive brittle failure, and sudden brittle failure are treated in detail. In each case, the original theory is briefly reviewed, and then its extensions accompanied by numerical examples are presented. Several limitations originally imposed by Hahn, such as the monotonically nonincreasing requirement on the failure strain curve, are lifted and the mathematical formulations are generalized. Some common …

Machining Of Composite Materials. Part Ii: Non-Traditional Methods, Serge Abrate, D. Walton

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Machining of composite materials is difficult due to the heterogeneity and heat sensitivity of the material and the high abrasiveness of the reinforcing fibers. This results in damage being introduced into the workpiece and very high tool wear. The use of traditional machining methods was reviewed in Part I of this paper. Here new methods are considered: laser, waterjet, electro-discharge, electro-chemical spark, and ultrasonic machining. These various techniques have been applied to organic matrix composites with aramid, glass, graphite fiber reinforcement but also to metal matrix and ceramic matrix composites. © 1992.

Machining Of Composite Materials. Part I: Traditional Methods, Serge Abrate, D. A. Walton

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Composite materials are more difficult to machine than metals mainly because they are anisotropic, non-homogeneous and their reinforcing fibers are very abrasive. During machining, defects are introduced into the workpiece, and tools wear rapidly. Traditional machining techniques such as drilling or sawing can be used with proper tool design and operating conditions. A review of traditional machining methods applied to organic and metal matrix composites is presented in this article. The use of non-traditional machining methods such as waterjet, laser and ultrasonic machining will be discussed in the second part. © 1992.

Effect Of Temperature On The Ultimate Strength And Modulus Of Whisker‐Reinforced Ceramics, Douglas R. Carroll, Lokeswarappa R. Dharani

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Whiskers are a very attractive means of reinforcing a ceramic material. It has been shown that the whiskers dramatically improve the ultimate strength and modulus of the materials at room temperature. However, recent studies indicate that at high temperatures the improvement is less pronounced, or there is no improvement at all. In this paper a model is developed to explain why the properties are degraded at high temperature. The parameters which seem most important for high‐temperature performance are the coefficients of thermal expansion and Poisson's ratios for the constituents, the heat treatment temperature, and the coefficient of friction between the …

An Analytical And Experimental Study Of Clearance And Bearing-Bypass Load Effects In Composite Bolted Joints, Rajiv Vikas Arun Naik

Mechanical & Aerospace Engineering Theses & Dissertations

A combined analytical and experimental study is conducted to determine the effects of clearance and bearing-bypass loading for mechanically fastened joints in composites. A simple method of analysis is developed to account for the nonlinear effects of bolt-hole clearance. The nonlinear load-contact variations for clearance-fit fasteners are also measured using specially instrumented fasteners. For a quasi-isotropic graphite/epoxy laminate, results show that the contact arc as well as the peak stresses around the hole and their locations are strongly influenced by the clearance. After a slight initial nonlinearity, the peak stresses vary linearly with applied load. The typical clearance levels are …