Date of Award
2026
Degree Type
Dissertation
Degree Name
Doctor of Philosophy in Mechanical Engineering and Applied Mechanics
Department
Mechanical, Industrial and Systems Engineering
First Advisor
Helio Matos
Abstract
The field of engineering has made momentous progress in the past 400 years, evolving from simple experiments to systematically analyze how materials break under stress, to full-field and point-wise measurements being simultaneously leveraged to study multiple phenomena during a single experiment. This experimental approach, coupled with carefully formulated analytical frameworks and well-constructed computational models, enables expansion of what can be accomplished with materials and structures. Nevertheless, these investigative approaches can become repetitive and devolve into academic exercises unless focused upon novel challenges that have practical use and require creativity of approach. In past decades, there has been no lack of literature devoted to analytical frameworks and computational models that study unique combinations of material properties and structural geometry. However, complimentary experimental investigations can be more difficult to locate, due to manufacturing limitations or lack of suitable materials at the time. Recently, the additive manufacturing method of 3D printing has been accelerating to fill this gap and open new horizons Even though it is still a highly experimental field, 3D printing is an established manufacturing method. It is highly versatile and is widely used in a vast range of applications from medical prosthetics to motorcycle shock absorbers. 3D printing is accomplished via both direct and indirect methods. Direct AM methods fall under seven main categories as outlined by the American Society for Testing and Materials. These categories are vat polymerization, material jetting, binder jetting, material extrusion, powder bed fusion, sheet lamination, and directed energy deposition. The techniques that are to be utilized for this work are powder bed fusion and material extrusion. Powder bed fusion is a method where thermal energy is used to combine areas of a powder bed according to the desired printing pattern. Of the various powder bed fusion techniques, selective laser sintering is commonly used. Material extrusion involves precisely distributing material through a nozzle. The primary mode of material extrusion is fused-deposition modeling (FDM), also known as fused-filament fabrication (FFF). This method allows for rapid manufacturing of unique structures that would be extremely difficult to produce via traditional methods.
The structures of interest in this work pertain to aerospace, defense, or structural applications in extreme environments. The structures of interest could include air or space vehicles, underwater submersibles, or superstructures-all of which may be expected to be exposed to extreme environments. Extreme environments are typically characterized by conditions involving one or more combinations of weathering, extreme levels of temperature, or high intensity or rates of loading. Extreme loading is especially of interest when considering that 3D printed or even flexible structures do not behave like traditional structures of similar geometry under such loading conditions. These structures can be made of polymers, carbon fiber materials, various metals and even neoprene rubbers, depending on the specific application. In the context of 3D printing, certain combinations of these materials can create 3D printing filaments which have some degree of electrical conductivity and could be utilized in the manufacturing of electro-mechanical systems.
The broad goal of this work is to effectively utilize experimental methods and also 3D printing to study how unique structures made of various materials behave under extreme loading. The extreme loading conditions were high levels of displacement, pressure, and velocity. The insights from the work performed are intended to inform expectations on how 3D printed or flexible structures behave under extreme loading. For 3D-printed structures, the insights can inform how to improve manufacturing.
Chapter 1 contains a study devoted to understanding how conductive 3D printing materials behave while undergoing extreme displacements. Electro-mechanical measurements were taken to understand the dependency of the electrical behavior on the mechanical performance. The study shows that adding conductive particles to the material, along with the Poisson effect can have a positive or negative impact on the electro-mechanical behavior depending on the level of strain that a material undergoes.
Chapter 2 focuses on the implosion behavior of 3D printed metallic cylinders that were produced by Selective Laser Melting (SLM). A computational model was developed to reduce iterations during the design process. High speed photography and dynamic pressure measurements were utilized to characterize the deformation behavior and effect on surrounding environment of the collapsing cylinders. This study showed that material properties, 3D printer, and printing parameters need to be thoroughly understood in order to obtain structures which behave as designed. Additionally, it was found that the 3D printed cylinders experienced localized failure, global buckling, or a combination of both mechanisms.
Chapter 3 presents an initial investigation into the structural response of 3D printed Carbon Fiber Reinforced Polymer (CFRP) plates that had an Archimedean Spiral Configuration (ASC) geometry. Using high-speed photography and dynamic sensors, the modal behavior and response to impact loading were investigated for clamped boundary conditions. The impact response of the plates was also compared to a twill-woven carbon fiber plate of comparable mass. The study found that the ASC geometry had good damage absorption and recovery for the velocity level that was investigated.
Chapter 4 is a novel investigation into the response of a submerged flexible membrane when subjected to underwater explosive (UNDEX) loading. The membrane served as an analog for an eardrum, lung, or similar system that a mammal underwater may possess. Explosives, high speed imaging, and dynamic pressure measurements were harnessed to determine the response of various curvatures of the membrane. The study found that the volume change of the membrane and explosion bubble were in phase, and that increasing curvature caused diametric deflection shapes.
Chapter 5 outlines the major conclusions of the previous chapters and the future directions that arise out of this work.
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Recommended Citation
Winnard, Thomas, "PERFORMANCE OF ADDITIVELY MANUFACTURED AND FLEXIBLE STRUCTURES IN EXTREME ENVIRONMENTS" (2026). Open Access Dissertations. Paper 4550.
https://digitalcommons.uri.edu/oa_diss/4550