Summer 2014 Research and Participants

Intumescing Trilayer Forms Nanobrick Wall to Create Flame Retardant for Polyurethane Foam

REU Student: Catherine E. Holmes, Christian Brothers University

Faculty Mentor: Dr. Jaime Grunlan

Grad Student Mentor: Amanda A. Cain, Craig R. Nolan

Upon ignition, polyurethane foam burns rapidly and spreads due to its propensity to melt drip, which causes a dangerous liquid fire.  In an effort to eliminate melt drip and inhibit the growth and further spread of the fire, a trilayer (TL) coating consisting of sodium montmorillonite (MMT), poly(allylamine hydrochloride) (PAH), and sodium hexametaphosphate (PSP) was developed using the layer-by-layer (LbL) method.  The flame retardant properties of the thin film were tested using a micro hand held butane torch and cone calorimetry.  Due to the intumescing behavior of the PAH and PSP, along with the thermal insulation from the MMT, it was found that the trilayer coating stopped the melt drip, slowed the progress of the flame, and reduced the peak heat release rate, as determined by cone calorimetry.  Film growth was characterized by ellipsometry and quartz crystal microbalance (QCM) in order to determine the thickness of the coating and the mass of each component deposited, respectively.  Further data was gathered using scanning electron microscopy (SEM) to better analyze the pre and post burn foam.  This study is another step towards better, more environmentally benign flame retardants

Data Acquisition of the Manually Operated Shock Tube Facility

REU Student: Eugene Kim, Rutgers University

Faculty Mentor: Dr. Rodney D.W. Bowersox

Post-doctoral Mentor: Dr. Jerrod W. Hofferth

Undergraduate Summer Research Grant Peer Researcher (USRG by TAMU College of Engineering): Corey L. Nelson, Clayton Brown

REU Student (from Mechanical Engineering) Peer Researcher: Leslie Prat

International Undergraduate Summer Research Student Peer Researcher: Indian Institute of Technology at Kanpur (IIT Kanpur/TAMU Exchange Program): Raghav Goyal

Five undergraduates collaborate to design and manufacture a manually piston-driven shock tube facility, which is currently capable of producing up to Mach 1.6 shock waves. The goal is to prepare an inexpensive, efficient, and educational shock tube for the scientific community. STUD, Shock Tube Undergraduate Design, is uniquely set apart from other shock tube designs because the operation requires a person to spin the handle, allowing the piston to drive forward, until the diaphragm bursts.

Data acquisition (DAQ), simple gathering of information about a system, plays a powerful role in all mechanical systems. To improve data acquisition of a mechanical system, the project focuses on efficiency, productivity, and cost. Following a modern PC-based DAQ system, the heart of this projects lies within National Instruments’ virtual measurement tool, LabVIEW. LabVIEW, a design virtual software, is used to build any measurement or control system in dramatically less time providing a more powerful, flexible, cost-effective measurement solution. In Texas A&M’s National Aerothermochemistry Laboratory, the STUD requires a data acquisition system for obtaining desired Mach number and rupture pressure. The instrumentation solely relies on the NI “PCI-6122”, which is a multifunctional DAQ hardware with four available channels. “PCI-6122” will connect to a Kulite pressure transducer, two PCB dynamic pressure sensors, and a K-type thermocouple. For more information about the instrumentation design of the STUD refer to Clayton Brown’s paper in the first reference. As for the mechanical design of the shock tube, go to the third reference written by Leslie Prat. Finally, for capturing an image of the shock wave through the test section will require a time triggering process requiring a pulse generator to input the delay.

Effect of Nanofibers on Composite Panels

REU Student: Kai Morikawa, Texas A&M University

Faculty Mentors: Dr. Mohammad Naraghi

In this project, the effect of polyacrolyonitrile (PAN) nanofibers on unidirectional carbon fiber reinforced composite panels was studied. Two types of composite panels were fabricated, bare and hybrid panels. For bare carbon fiber composite panels, the fabrication method used was vacuum assisted resin transfer molding (VARTM).  On hybrid carbon fiber composite panels, PAN nanofibers were electrospun on each carbon fiber layer, then composite panels were prepared via VARTM. The VARTM fabrication method utilizes a vacuum in order to prepare a composite panel. The vacuum assists in the distribution of epoxy resin throughout the carbon fiber layers. Afterwards, a tensile test was performed on each type of composite panel. The material properties recorded in this work were elastic modulus, toughness, and tensile strength. The nanofibers that were in the hybrid carbon fiber composite panels effectively changed the material properties of the composite.

Characterization of Notch Sensitivity on the Mechanical Behavior and Fracture of Nanocomposites

REU Student: William Ochoa, Texas A&M University

Faculty Mentors: Dr. Amine BenzergaDr. Mohammad Naraghi

Grad Student Mentor: Frank Gardea

The purpose of this research is to study the effect of stress triaxiality, plastic deformation, and fracture strength on notched tensile nanocomposite specimens. The methods used to fabricate the nanocomposite specimens along with initial tensile test results will be presented in this report. The material constituents of the nanocomposite specimens are: EPON 862 epoxy resin, EPIKURE W curing agent, and Pyrograf-III Carbon Nanofibers. The carbon nanofibers (CNFs) are embedded into a thermoset epoxy matrix with the orientation of the CNFs controlled via an externally applied electric field. Tensile tests were performed on notched aligned CNF composites as initial experiments in a set of larger tests.

The Effect of Polishing on the Thermo Mechanical Fatigue Response of Nickel-Titanium-Hafnium Shape Alloy Actuators

REU Student:  Chad H. Reinart, Embry-riddle University

Faculty Mentor: Dr. Dimitris Lagoudas

Post-doctoral Mentor: Theocharis Baxevanis

Grad Student Mentor: Robert W. Wheeler

Shape Memory Alloys (SMAs) have a promising future for use in many different fields of engineering ranging from biomedical to aerospace. This can be accredited to their ability to sustain and recover from large deformations as well as their high actuation energy density. With these additional functions, SMAs have been shown to significantly reduce the weight, emissions, and complexity of commercial aircraft systems. For SMAs to be utilized in critical components, the active material community must have a better understanding of actuation fatigue. The purpose of this study was to analyze the effects of different material surface treatments on the actuation fatigue response of Nickel Titanium Hafnium (NiTiHf) and use the characterization data collected to calibrate a previously developed constitutive damage model for multiple stress levels. Dogbone actuators were cut from extruded NiTiHf rods using Electro Discharge Machining (EDM) and then a portion of the actuators were chemically, mechanically, and electro-polished. The actuators were subjected to actuation fatigue via mechanical loading, joule heating, and convective cooling. A constant load was applied to the actuators using suspended weights before being thermally cycled to full actuation with a feedback (displacement and temperature) control scheme developed in LabView. Actuation fatigue life results of a test matrix consisting of both polished and unpolished specimens are presented. General trends within actuation strain and cycles to failure were observed in both polished and unpolished specimens. Post mortem microscopic analysis of failed specimens showed that the surface defects in the EDM recast layer resulted in large, non-critical crack formation. The beneficial effects of the compressive recast layer overshadowed the adverse effects of the recast layer on the overall fatigue response.