Engineering Commons^™

Development Of A High-Pressure Infiltration Process For Phenol–Formaldehyde Matrix Composites, Samuel Weiler, Patrick Schwartzkopf, Henry Haffner, K. Chandrashekhara

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Phenol–formaldehyde (phenolic) thermosets are known for excellent heat and chemical resistance, high flame retardance, and good mechanical performance. However, phenolics are also known for their high brittleness, and tendency to form voids, due to a condensation reaction forming water during curing. These voids can decrease the mechanical performance of the resultant phenolic composite and introduce undesirable performance characteristics. This work aims to develop a technique that uses high-pressure infiltration to obtain dense phenolic matrix composites, with commercially available resin and fiber reinforcement. The high-pressure system developed in this work is compared to a conventional low-pressure resin infusion technique, and the …

Autonomous Navigation Of The Surface Autonomous Vehicle For Emergency Rescue (Saver), Andrew Skow

ENGS 88 Honors Thesis (AB Students)

Once dropped into the ocean, SAVER will autonomously navigate towards the Advanced Next-Generation Emergency Locator beacon, worn by every NASA astronaut, that emits a 121.5 MHz distress signal. Using a rotating directional loop antenna SAVER is able to detect and identify the direction of the distress beacon and navigate itself towards the signal source. The autonomous navigation system is dependent on several electrical, and mechanical systems to function properly and presents a novel systems engineering problem. Given testing limitations, NASA requires that SAVER is designed to operate indoors and with an umbilical power supply. The radio direction finding (RDF) system …

Double-Sided Corrugated Composite Tube And Axle Protective Mechanism For Railway Vehicles, Hozhabr Mozafari

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Structural elements in transportation vehicles are exposed to different types of dynamic loadings and impact scenarios. Protecting passengers against injury and providing mechanisms to avoid impact induced damages to the critical components are the two hot topics in crashworthiness engineering. The presented research work includes two parts. The first part is about designing a novel double-sided composite corrugated tube that can be implemented in front chassis rail of ground vehicles to improve their crashworthiness against collision and car accidents. To maximize the controllable energy absorption of corrugation troughs as observed in the single sided corrugated (SSC) tube, we proposed and …

Synthesis Of Multiwall Α-Fe2o3 Hollow Fibers Via A Centrifugal Spinning Technique, Mandana Akia, K. A. Mkhoyan, Karen Lozano

Mechanical Engineering Faculty Publications and Presentations

Highlights

• Hollow hematite (α-Fe2O3) fine fibers were fabricated via a simple, flexible, and scalable technique.

• An aqueous solution with iron precursor/polymer was used in the centrifugal spinning process

• Developed fibers show average wall thickness of 55 ± 15 nm and outer fiber diameter of 852 ± 86 nm

Abstract

Hollow hematite (α-Fe2O3) fine fibers with multiwall structure were synthesized by utilizing a centrifugal spinning technique. Aqueous solutions of polyvinyl pyrrolidone and iron (III) nitrate nonahydrate were prepared and spun into fibers. The precursor fibers were heat treated at 650 °C to form iron oxide fibers. Scanning electron micrographs revealed the …

Resistance To Helium Bubble Formation In Amorphous Sioc/Crystalline Fe Nanocomposite, Qing Su, Tianyao Wang, Jonathan Gigax, Lin Shao, Michael Nastasi

Department of Mechanical and Materials Engineering: Faculty Publications

The management of radiation defects and insoluble He atoms represent key challenges for structural materials in existing fission reactors and advanced reactor systems. To examine how crystalline/amorphous interface, together with the amorphous constituents affects radiation tolerance and He management, we studied helium bubble formation in helium ion implanted amorphous silicon oxycarbide (SiOC) and crystalline Fe composites by transmission electron microscopy (TEM). The SiOC/Fe composites were grown via magnetron sputtering with controlled length scale on a surface oxidized Si (100) substrate. These composites were subjected to 50 keV He+ implantation with ion doses chosen to produce a 5 at% peak He …

Novel Structural Health Monitoring And Damage Detection Approaches For Composite And Metallic Structures, Shervin Tashakori

FIU Electronic Theses and Dissertations

Mechanical durability of the structures should be continuously monitored during their operation. Structural health monitoring (SHM) techniques are typically used for gathering the information which can be used for evaluating the current condition of a structure regarding the existence, location, and severity of the damage. Damage can occur in a structure after long-term operating under service loads or due to incidents. By detection of these defects at the early stages of their growth and nucleation, it would be possible to not only improve the safety of the structure but also reduce the operating costs. The main goal of this dissertation …

Material State Awareness For Composites Part Ii: Precursor Damage Analysis And Quantification Of Degraded Material Properties Using Quantitative Ultrasonic Image Correlation (Quic), Subir Patra, Sourav Banerjee

Faculty Publications

Material state awareness of composites using conventional Nondestructive Evaluation (NDE) method is limited by finding the size and the locations of the cracks and the delamination in a composite structure. To aid the progressive failure models using the slow growth criteria, the awareness of the precursor damage state and quantification of the degraded material properties is necessary, which is challenging using the current NDE methods. To quantify the material state, a new offline NDE method is reported herein. The new method named Quantitative Ultrasonic Image Correlation (QUIC) is devised, where the concept of microcontinuum mechanics is hybrid with the experimentally …

Material State Awareness For Composites Part I: Precursor Damage Analysis Using Ultrasonic Guided Coda Wave Interferometry (Cwi), Subir Patra, Sourav Banerjee

Faculty Publications

Detection of precursor damage followed by the quantification of the degraded material properties could lead to more accurate progressive failure models for composite materials. However, such information is not readily available. In composite materials, the precursor damages—for example matrix cracking, microcracks, voids, interlaminar pre-delamination crack joining matrix cracks, fiber micro-buckling, local fiber breakage, local debonding, etc.—are insensitive to the low-frequency ultrasonic guided-wave-based online nondestructive evaluation (NDE) or Structural Health Monitoring (SHM) (~100–~500 kHz) systems. Overcoming this barrier, in this article, an online ultrasonic technique is proposed using the coda part of the guided wave signal, which is often neglected. Although …

Effect Of Ultrasonic Treatment On The Microstructure And Mechanical Properties Of Al6061 And Composite, Ana S. Exime

FIU Electronic Theses and Dissertations

In this study, the effect of ultrasonic treatment (UST) parameters such as amplitude, sonication time, and melt temperature on microstructure and microhardness of Al 6061 alloy is evaluated. The effect of UST on the dispersion of tungsten disulfide (WS₂) and carbon nanotubes (CNT) as reinforcement particles in Al 6061 during casting is also studied. The cast Al 6061 with UST demonstrated 32% grain size reduction and 8% increase in the microhardness for optimum processing conditions. The cavitation process induced by UST is responsible for the refinement in microstructure and increase of hardness by enhancing the degassing and nucleation …

Aluminum Matrix Syntactic Foam Fabricated With Additive Manufacturing, M. Spratt, Joseph William Newkirk, K. Chandrashekhara

Materials Science and Engineering Faculty Research & Creative Works

Syntactic foams are lightweight structural composites with hollow reinforcing particles embedded in a soft matrix. These materials have applications in transportation, packaging, and armor due to properties such as relatively high specific stiffness, acoustic dampening, and impact absorption. Aluminum matrices are the most widely studied of metal matrix syntactic foams, but there is little to no research in regards to processing the foams with additive manufacturing. It is theorized that the fast cooling rates and limited kinetic energy input of additive could reduce two issues commonly associated with processing syntactic foams: microsphere flotation in the melt and microsphere fracture during …

Open Source Multi-Head 3d Printer For Polymer-Metal Composite Component Manufacturing, J. Laureto, Joshua M. Pearce

Department of Materials Science and Engineering Publications

As low-cost desktop 3D printing is now dominated by free and open source self-replicating rapid prototype (RepRap) derivatives, there is an intense interest in extending the scope of potential applications to manufacturing. This study describes a manufacturing technology that enables a constrained set of polymer-metal composite components. This paper provides (1) free and open source hardware and (2) software for printing systems that achieves metal wire embedment into a polymer matrix 3D-printed part via a novel weaving and wrapping method using (3) OpenSCAD and parametric coding for customized g-code commands. Composite parts are evaluated from the technical viability of manufacturing …

Effect Of Airfoil And Composite Layer Thicknesses On An Aerostructural Blade Optimization For Wind Turbines, Ryan Barrett, Ian Freeman, Andrew Ning

Faculty Publications

The purpose of this research is to enhance the performance of wind turbine blades by exploring the effect of adding airfoil and material layer thicknesses to the optimization design process. This is accomplished by performing an aerostructural blade optimization to minimize mass over annual energy production and thereby reduce the cost of energy. Changing airfoil thickness allows the airfoil shape to evolve as part of the optimization. The airfoil thicknesses are allowed to vary within two airfoil families, the TU-Delft and NACA 64-series, that are used in the NREL 5-MW reference turbine. Both experimental wind tunnel and computational data are …

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 …