Mechanical Engineering Commons^™

Characterization Of Carbon-Fiber Reinforced Polyetherimide Thermoplastic Composites Using Mechanical And Ultrasonic Methods, Mohannad A. Alhaidri

Theses and Dissertations

Continuous fiber-reinforced thermoplastics (CFRT) have the potential for being a mass-produced material for high-performance applications. The primary challenge of using CFRT is achieving fiber wet-out due to the high viscosity of thermoplastics. This results in higher temperatures and pressures required for processing the composites. Co-mingling thermoplastic fibers with a reinforcing fiber, potentially, can enable better wetting by reducing the distance the matrix needs to flow. This could result in shorter cycle times and better consolidation at lower temperatures and pressures. In this study, a polyetherimide (PEI) fiber was comingled with carbon fibers (CF). The resultant fibers were woven into fabrics …

Microstructural Factors Of Strain Delocalization In Model Metallic Glass Matrix Composites, Thomas James Hardin

Theses and Dissertations

Metallic glass matrix composites have enormous potential stemming from the interplay between crystalline and amorphous phases. This work models such a composite using shear transformation zone dynamics (a modified kinetic Monte Carlo method) for the amorphous phase, and a local Taylor dislocation model for the crystalline phase. An N-factorial experiment using the model is presented examining the effects of crystalline volume fraction, microstructure length scale, and yield stress of the crystalline phase. Each replicate is analyzed for maximum stress, maximum strain, strain energy dissipation, strain localization, and strain partitioning between phases. Regression analysis is used to identify statistically-significant trends in …

Formula Sae Hybrid Carbon Fiber Monocoque / Steel Tube Frame Chassis, Matthew Hagan, John Rappolt, John Waldrop

Mechanical Engineering

The Cal Poly Formula SAE Team created this project in order to design and fabricate a high-performance chassis which would be competitive at 2013 FSAE Lincoln, and to document the process so that future teams could more easily create a chassis. One of the main goals was to reduce weight from the 143- lb 2012 chassis subsystem. A weight of 95 lb was achieved, with 82 lb in the chassis structure itself and a predicted torsional stiffness of 1700 lb*ft/deg. Composite materials design and manufacturing techniques were developed during the project. Design, testing, and manufacturing processes are detailed, and results …

Stress Corrosion Cracking In Polymer Matrix Glass Fiber Composites, Jonathan Kosak

Electronic Theses and Dissertations

With the use of Polymer Matrix Glass Fiber Composites ever expanding, understanding conditions that lead to failure before expected service life is of increasing importance. Stress Corrosion Cracking (SCC) has proven to be one such example of conditions found in use in high voltage transmission line applications that leads to brittle fracture of polymer matrix composites.

SCC has been proven to be the result of acid buildup on the lines due to corona discharges and water buildup. This acid leaches minerals from the fibers, leading to fracture at low loads and service life. In order to combat this problem, efforts …

16th Annual Sampe Student Bridge Contest: Design Of A Wood Core Flax Fiber-Reinforced Composite I-Beam, Robert J. Wagner

Honors Theses

The goal of this project was to demonstrate the applicability of natural composites in structural applications for objects with shorter intended life spans such as sports equipment. This was done by competing in the 16th Annual SAMPE Student Bridge Contest with a natural fiber, natural core composite I-beam in Long Beach, California on May 8th, 2013. The beam was to withstand 3,000 lbs under three-point-bending while maintaining a low weight. In order to compete, natural reinforcement fibers, natural core materials and a bonding matrix had to be identified; a beam within allowable contest dimensions had to be designed; and a …

Variational Asymptotic Method For Unit Cell Homogenization Of Thermomechanical Behavior Of Composite Materials, Chong Teng

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

To seek better material behaviors, the research of material properties has been massively carried out in both industrial and academic fields throughout the twentieth century. Composite materials are known for their abilities of combining constituent materials in or- der to fulfill the desirable overall material performance. One of the advantages of composite materials is the adjustment between stiffness and lightness of materials in order to meet the needs of various engineering designs. Even though the finite element analysis is mature, composites are heterogeneous in nature and can present difficulties at the structural level with the acceptable computational time. A way …

Effects Of Partial Confinement And Local Heating On Healing Efficiencies Of Self-Healing Particulate Composites, Jonah Champagne

LSU Master's Theses

Shape memory polymers are smart materials that can be trained to hold a temporary shape through programming and regain their original shape upon heating. Since there discovery in the 1960s, much research has been devoted to the study of these polymers. Of particular interest in recent years is the study of self-healing shape memory polymers. In a previous study, it has been shown that in order for efficient healing to take place in self-healing shape memory polymers, confinement during healing is essential. Moreover, a two-step close-then-heal (CTH) approach to healing was suggested. It was shown that use of this CTH …

Biaxial & Twist Testing Of Composite Carbon-Fiber Sandwich Panels For Automotive Racing Vehicles, Erik Eckberg

Materials Engineering

Composite sandwich panels were constructed with 4-ply plain weave carbon-fiber/epoxy face sheets in the 0^o/45^o/0^o/45^o orientation and 1/8^th inch Nomex honeycomb core. The panels were cut into 5-inch square test plates for mechanical testing. All testing was done on a fixture designed and fabricated by Pratt & Miller Engineering and installed on an Instron testing system at Cal Poly. The twist test was performed by supporting diagonal corners of the plate while simultaneously loading the opposite two corners at a crosshead rate of .06 in/min (ASTM 3044-94R11). Out of 10 panels tested, …

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.

An Investigation Of Damage Arrestment Devices On Carbon Fiber Sandwich Specimens Under Dynamic Loading, Gabriel Sabino Sanchez

Master's Theses

This research studies the effects of a damage arrestment device embedded between a carbon fiber facesheet and foam core to find whether there is an increase in the structural integrity of the sandwich composites. Experimental and theoretical finite element analyses are implemented for two different composite sandwich geometries; plates and beams. Each structure consisted of the same loading criteria and was restricted to the same vibration fixture during the experiment. An accelerometer was placed on the composite plate to record the amplitude and the natural frequencies of the composite structure. Each composite specimen is then fixed to the surface of …

Advanced Design Optimization For Composite Structure: Stress Reduction, Weight Decrease And Manufacturing Cost Savings, Shayan Ahmadian

Master's Theses

An injection moldable chopped fiber composite actuator with detailed drawing and tolerances was designed within one year. A vendor was selected and a quote for injection molding tooling cost for production was obtained and the first prototype was built in addition of six months. The risks are identified and material characterization tests are proposed.

The objective of this project was redesigning an aluminum made actuator with a continuous fiber composite for weight saving purposes. After searching the literature and consulting with experts in the field it was concluded that manufacturing costs associated with continuous fiber composite are 3 times as …

Compressive Strength Of Continuous Fiber Unidirectional Composites, Ronald Thompson

All Dissertations

Dow and Rosen's work in 1965 formed an intellectual framework for compressive strength of unidirectional composites. Compressive strength was explained in terms of micro-buckling, in which filaments are beams on an elastic foundation. They made simplifying assumptions, with a two dimensional idealization and linearized material properties. This study builds on their model, recognizing that the shear mode of instability drives unidirectional compressive strength. As a necessary corollary, the predictive methods developed in this study emphasize correct representation of composite shear stiffness. Non-linear effects related to matrix material properties, fiber misalignment, three dimensional representation, and thermal prestrains are taken into account. …

Peridynamic Models For Dynamic Brittle Fracture, Wenke Hu

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Damage and failure in composite materials under dynamic loading has been extensively studied in experiments for several decades. Composite materials exhibit various damage and failure patterns under different loading rates, such as splitting and branching. Classical models cannot directly be applied to problems with discontinuous fields. A new nonlocal continuum model, peridynamics, has been proposed with the goal of solving dynamic fracture problems.

The J-integral has the physical significance of energy flow into the crack tip region. We present a rigorous derivation for the formulation of the J-integral in peridynamics using the crack infinitesimal virtual extension approach. We …

Constrained Layer Damping Of Honeycomb Composite Structures, Rohit Telukunta

All Theses

Composite sandwich structures have replaced homogenous dense solids in many applications due to their advantages of high stiffness to weight ratio, and higher damping characteristics. Higher damping in engineering applications is desirable to reduce structural vibrations. The application of a viscoelastic layer between two thin face sheets gives rise to the concept of constrained layer damping which is an effective technique to achieve increased damping in engineering applications.
Honeycomb cellular structures are often used for the core in sandwich construction because of their low density and high stiffness properties. Regular honeycombs are defined by conventional hexagonal geometry, which gives rise …

Thermodynamic Approach To Fatigue Failure Analysis In Metals And Composite Materials, Mehdi Naderi Abadi

LSU Doctoral Dissertations

Fatigue is a dissipative process and must obey the laws of thermodynamics. In general, it can be hypothesized that the degradation of machinery components is a consequence of irreversible thermodynamic processes that disorder a component, and that degradation is a time dependent phenomenon with increasing disorder. This suggests that entropy —a fundamental parameter in thermodynamics that characterizes disorder— offers a natural measure of component degradation. The majority of the existing methods for prediction of fatigue are limited to the study of a single fatigue mode, i.e., bending or torsion or tension-compression. Further, the variability in the duty cycle in a …

An Investigation Of Initially Delaminated Composite Sandwich With Delamination Arrest Mechanism Under Buckling Loading, Tony D. Tran

Master's Theses

This thesis involves the development of a fiberglass-foam composite sandwich structure with the introduction of delamination arrestment keys; therefore, a study of an initially delaminated composite sandwich structure was the experimental analysis on multiple configurations in how the arrestment keys are placed.

The first part of this thesis research was to the experimental design and manufacturing of the composite sandwich plates. These plates were later cut down to the specific test dimensions and manufacturing processes for the composite sandwich plates and test specimens were created. The composite sandwich plates were manufactured using a vacuum resin infusion process. The dimensions of …

Natural Fibers And Fiberglass: A Technical And Economic Comparison, Justin Andrew Zsiros

Theses and Dissertations

Natural fibers have received attention in recent years because of their minimal environmental impact, reasonably good properties, and low cost. There is a wide variety of natural fibers suitable for composite applications, the most common of which is flax. Flax has advantages in tensile strength, light weight, and low cost over other natural fibers. As with other natural and synthetic fibers, flax is used to reinforce both thermoset and thermoplastic matrices. When flax is used in thermoplastic matrices, polypropylene and polyethylene are the main resins used. Although at first glance flax may seem to be a cheaper alternative to fiberglass, …

Human Powered Helicopter, Brenton Haven, Daniel Hudson, Eli Knight

Mechanical Engineering

Fall of 2009, The Cal Poly Aircraft Construction club restarted Cal Poly's quest for the Sikorsky prize. The Sikorsky prize rewards the first a human powered helicopter to sustain controlled hover for one minute without stored energy. Throughout the 1980’s, Cal Poly made three attempts; the most successful being the DaVinci III. Also, the DaVinci III was the first ever publically recognized successful human powered helicopter to leave the ground. This scope of this project is to improve the DaVinci III fuselage and drivetrain for the DaVinci IV. The DaVinci IV adopts the DaVinci III system layout and improves both …

Composite Suspension For Formula Sae Vehicle, Reid Olsen, Andrew Bookholt, Eric Melchiori

Mechanical Engineering

This senior project report describes how a redesign of the 2008 Cal Poly Formula SAE vehicle's suspension components was conducted using carbon fiber components.

Characterization Of Composite Piezoelectric Materials For Smart Joint Applications, Hari Prasad Konka

LSU Master's Theses

Piezoelectric materials have the ability to provide desired transformation from mechanical to electrical energy and vice versa. When a mechanical force is applied to the piezoelectric material an electrical voltage is generated and when an electrical voltage is applied to the piezoelectric material it gets strained or deformed. Owing to these characteristics piezoelectric materials can be used as a sensor, an actuator, as well as a power generation unit. The high brittleness property of the original piezoelectric material is one of the major constraints in using them in the engineering applications. In order to overcome this disadvantage the composite piezoelectric …

The Cryogenic Bonding Evaluation At The Metallic-Composite Interface Of A Composite Overwrapped Pressure Vessel With Additional Impact Investigation, Eric A. Clark

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A bonding evaluation that investigated the cryogenic tensile strength of several different adhesives / resins was performed. The test materials consisted of 6061 aluminum test pieces adhered to a wet-wound graphite laminate in order to simulate the bond created at the liner-composite interface of an aluminum lined composite overwrapped pressure vessel. It was found that for cryogenic applications, a flexible, low modulus resin system must be used. Additionally, the samples prepared with a thin layer of cured resin – or prebond – performed significantly better than those without. It was found that it is critical that the prebond surface must …

Composite Manufacturing Of Small Wind Turbine Blades- Utility Scale Methods Applied To Small Wind, Bryan Kyle Edwards

Master's Theses

Cal Poly, San Luis Obispo’s first wind turbine explores the methods and processes that are employed to manufacture utility scale wind turbines, and applies them to small scale wind turbines. The primary objective is to promote the development of small scale wind turbine blades in ways that resemble, as closely as possible, the construction and methods of utility scale turbine blade manufacturing. Vacuum infusion is employed to create a hollow, multi piece, lightweight design using carbon fiber and fiberglass with an epoxy based resin. A “rapid prototyping” method is developed using high density foam molds that allows short cycle time …

Performance Analysis And Life Prediction For Small Wind Turbine Blades: A Wood Laminate Case Study, Christopher James Nosti

Master's Theses

A detailed study of the fatigue life of wooden wind turbine blades for a new 10 kilowatt system was undertaken. A numerical model of the blades was created using the technical software package MATLAB in order to estimate the maximum stress occurring within the blade in response to changes in wind velocities based on a wind profile approximating the location where these turbines are expected to operate. The material properties of the wooden laminate were measured using an Instron tensile test machine and were found to be in line with published values. In parallel with this effort, a three dimensional …

Tribo-Surface Characteristics Of Al-B4c And Al-Sic Composites Worn Under Different Contact Pressures

A.S. Md Abdul Haseeb

Tribo-surface characteristics of two aluminium metal matrix composites (Al-MMC) of compositions Al-13 vol%B4C and Al-13 vol%SiC sliding against a commercial phenolic brake pad have been investigated under dry conditions. The wear tests were carried out using a pin-on-disc type apparatus at a linear speed of 1.62 m s-1 under contact pressures ranging from 0.75 to 3.00 MPa. The coefficient of friction was recorded on line. Wear rates were calculated from mass loss measurements. Scanning electron microscope equipped with energy dispersive X-ray spectroscopy was used to examine the tribo-surface. It is found that wear rate of both composites increases with increasing …

Velocity Effects On The Wear, Friction And Tribochemistry Of Aluminum Mmc Sliding Against Phenolic Brake Pad

A.S. Md Abdul Haseeb

Two aluminum metal matrix composites (MMC) reinforced with 13 vol.% of SiC or B4C particles were made by stir casting followed by hot extrusion. Effects of sliding velocity on the wear, friction and tribochemistry of the worn surfaces of both composites sliding against a commercial phenolic brake pad have been investigated under dry condition. The wear tests were carried out using a pin-on-disc type apparatus at two linear sliding speeds: 1.62 and 4.17 m s-1 under a constant contact pressure of 0.75 MPa for a sliding distance of 5832 m. The coefficient of friction was recorded and wear rate of …

Velocity Effects On The Wear, Friction And Tribochemistry Of Aluminum Mmc Sliding Against Phenolic Brake Pad

A.S. Md Abdul Haseeb

Two aluminum metal matrix composites (MMC) reinforced with 13 vol.% of SiC or B4C particles were made by stir casting followed by hot extrusion. Effects of sliding velocity on the wear, friction and tribochemistry of the worn surfaces of both composites sliding against a commercial phenolic brake pad have been investigated under dry condition. The wear tests were carried out using a pin-on-disc type apparatus at two linear sliding speeds: 1.62 and 4.17 m s-1 under a constant contact pressure of 0.75 MPa for a sliding distance of 5832 m. The coefficient of friction was recorded and wear rate of …

Buckling Analysis Of Grid Stiffened Composite Structures, Samuel Kidane

LSU Master's Theses

Buckling of a stiffened composite cylinder is a very complex phenomenon that involves complex interactions between the skin and the stiffeners. Depending on different configurations of the skin and stiffener, different buckling failure modes and failure loads are observed in stiffened cylinders. In this work failure modes and buckling loads of stiffened composite cylinders under uniaxial loading condition is investigated by using analytical and experimental approaches. In the first Chapter an improved smeared method is developed to model the buckling problem of an isogird stiffened composite cylinder. In this model the stiffness contributions of the stiffeners is computed by analyzing …

Thin-Layer Prestressed Composite Ferroelectric Driver And Sensor Characterization With Application To Separation Flow Control, Karla M. Mossi

Mechanical & Aerospace Engineering Theses & Dissertations

Experiments were conducted in two different stages--general piezoelectric actuator characterization and flow separation control applications. The characterization of the piezoelectric devices was performed in several stages, due to the many variables that affect performance. The first stage of the characterization consisted of tests conducted on 13 different THUNDER^TM (thin-layer composite unimorph ferroelectric driver and sensor) configurations. These configurations consisted of a combination of 1, 3, 5, 7, and 9 layers of 25μ thick aluminum as backing material, with and without a top layer of 25μ aluminum. All of these configurations used the same piezoelectric ceramic wafer (PZT-5A) with dimensions …

Impression Creep Behavior In Weldments, S.H. Wang

Journal of Marine Science and Technology

At high temperature application, the failures of dissimilar metal weldments associated with the relevant degradation processes, which include chemical diffusion, oxide notching, precipitation, softening of the heat affected zone (HAZ), and creep type voids leading to cracking. This reveals that a creep in a gradient related to the microstructural degradation exists. The impression creep test was applied to monitor the effects of microstructural gradients on the localized high temperature creep properties in an autogeneous GTA aluminum weldment, and an austenitic stainless steel to ferritic steel dissimilar metal weldment respectively. To simplify the complexity of microstructural gradients, multipass weldments in A36 …

Fiber Enhanced Viscoelastic Damping Polymers And Their Application To Passive Vibration Control, Houchun Xia

Mechanical & Aerospace Engineering Theses & Dissertations

A new composite damping material is investigated, which consists of a viscoelastic matrix and high elastic modulus fiber inclusions. This fiber enhanced viscoelastic damping polymer is intended to be applied to light-weight flexible structures as surface treatment for passive vibration control. A desirable packing geometry for the composite material is proposed, which is expected to produce maximum shear strain in the viscoelastic damping matrix. Subsequently, a micromechanical model is established in which the effect of fiber segment length and relative motion between neighboring fibers are taken into account. Based on this model, closed form expressions for the effective storage and …