Mechanical Engineering Commons^™

Towards Modeling Of Induction Welding Of Thermoplastic Laminates With A Mixed Finite Element Boundary Element Approach, Florentius Johannes Van Zanten

Theses and Dissertations

There is an increased interest in induction welding of carbon fiber reinforced thermoplastic composite laminates within the aerospace industry. Currently, optimal manufacturing process parameters (e.g., current, power, and frequency settings, coil movement speed, etc.) are determined through an experimental trial-and-error approach. To reduce the need for an experimental approach that can determine the manufacturing process parameters, which would be expensive in both time and money, accurate and computationally efficient numerical tools are desired. This research is focused on improving the existing numerical tool, WelDone, in regard to its speed and accuracy.

WelDone utilizes a hybrid element formulation that combines traditional …

Development Of An Origami Inspired Composite Deployable Structure Utilizing Compliant Joints As Surrogate Folds, Samuel Porter Smith

Theses and Dissertations

This work presents the design and construction of a self-deployable, self-stiffening,and retractable (SDSR) space array from carbon fiber reinforced polymers (CFRP’s) and a working prototype is demonstrated. The effort required developing principles for the design of high-strain composite flexural joints and their integration into angled composite panels. Designing LET arrays in angled panels is explored. Analysis of simple composite LET joints is presented for two degrees of freedom. Validation of the composite LET modeling is sought through numerical methods and empirical testing. Testing of several composite LET joint specimens is conducted and the results are reported. Results indicate that (while …

Lamb Wave Nondestructive Evaluation And Imaging On Plate-Like Structures, Zhaoyun Ma

Theses and Dissertations

Structure components are designed with a certain service life and damage may occur, or they may come with manufacture defects. Such damage and defects may lead to structural failure if not detected in time. To ensure the structural safety and prevent catastrophic failure, effective inspection is critical for in-time maintenance. Nondestructive evaluation (NDE) and structural health monitoring (SHM) have been widely applied for damage inspection and evaluation in various industries due to their noninvasive nature. Lamb wave based NDE/SHM has become the most popular ultrasonic methods that has been proved effective in different engineering applications that can be used to …

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 …

Non-Destructive Evaluation Of Composites: Predictive Ultrasonic Guided-Waves Modeling, Non-Destructive Material Characterization, And The Application To Aerospace Structures, Darun Barazanchy

Theses and Dissertations

To predict guided wave dispersion curves, it is common to use different solution approaches depending on the material type (isotropic or anisotropic) of the medium in which the wave propagates. The two different solution methods are defined in different domains, frequency-phase velocity domain for isotropic materials and wavenumber-phase velocity domain for anisotropic materials. This may lead to difficulties and unsatisfying results when predicting the dispersion curves for hybrid laminates which contain both isotropic and anisotropic materials. Therefore, a unified formulation defined in the wavenumber-phase velocity domain to accomodate both isotropic and anisotropic materials, as well as hybrid combinations, is desired. …

Wetting, Superhydrophobicity, And Icephobicity In Biomimetic Composite Materials, Vahid Hejazi

Theses and Dissertations

Recent developments in nano- and bio-technology require new materials. Among these new classes of materials which have emerged in the recent years are biomimetic materials, which mimic structure and properties of materials found in living nature. There are a large number of biological objects including bacteria, animals and plants with properties of interest for engineers. Among these properties is the ability of the lotus leaf and other natural materials to repel water, which has inspired researchers to prepare similar surfaces. The Lotus effect involving roughness-induced superhydrophobicity is a way to design nonwetting, self-cleaning, omniphobic, icephobic, and antifouling surfaces. The range …

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 …

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 …