Structural Materials Commons^™

Stress Singularity Study Of Functionally Graded Material Based On Coherent Gradient Sensing Method, Jinjun Zhang

Kevin Lee

Numerical Studies For Improving Fracture Toughness Resistance Curve Testing Using Single-Edge (Notched) Tension Specimens, Yifan Huang

Electronic Thesis and Dissertation Repository

The fracture toughness resistance curve, i.e. the J-integral resistance curve (J-R curve) or the crack tip opening displacement resistance (CTOD-R) curves, is widely used in the integrity assessment and strain-based design of energy pipelines with respect to planar defects (i.e. cracks). This thesis deals with issues related to the experimental determination of the J(CTOD)-R curves using the newly-developed single-edge (notched) tension (SE(T)) specimens. In the first study, the plastic geometry factor, i.e. the η_pl factor, used to evaluate J in a J-R curve test based on the SE(T ...

Thermal Damage Approach Of Concrete: Application To Specimens Subjected To Combined Compressive And High Temperature Loads, Abdellah Menou, Ghassan Mounajed, Hocine Boussa, Christian La Borderie, Khalid Lafdi

Khalid Lafdi

Within the framework of study of concrete structures subjected to fire, .a theoretical and experimental work was conducted. The aim of this study was to investigate and to model the damage mechanisms of concrete after their exposure to high temperatures. The multiphase Digital Concrete Model as well as the damage model, MOD EV, which were both implemented on the finiteelem~ rit software package, SYMPHONIE, were used simμltaneously to assess the thermal damage of the concrete. In order to validate the thermal damage model, an experimental investigation was performed. The mechanical characteristics of 5 cementitious materials, which included cement paste, mortar ...

Koh Etching Of (100) Si Wafer, No 2, Inayat Bajwa

Protocols and Reports

This report describes KOH etching of (100) Si wafer through a hard mask of silicon oxide, and reveals that the scattered etch rate is ascribed to the etch rates of the different crystal planes exposed during the etching.

Evaluation Of Strain Distortion Correction Protocol Using Scanning Electron Microscopy And Digital Image Correlation, Alexandra Mallory, Alberto Mello, Michael Sangid

The Summer Undergraduate Research Fellowship (SURF) Symposium

Scanning electron microscopy in combination with digital image correlation (SEM-DIC) is a useful technique for measuring strain in materials at the micro-scale. In particular, it can be used to identify micro-scale strain localizations that are the precursor to material failure. While SEM produces high resolution images of the microstructure, the images also contain a large amount of distortion that, during DIC, will result in distorted strain values that require correction. In this project, a nickel-based alloy underwent cyclic mechanical fatigue at three different high temperatures to a targeted maximum strain. Scanning electron microscopy imaging was done on a 200x150μm area ...

Metamodels Of Residual Stress Buildup For Machining Process Modeling, Stuart B. Mccrorie, Michael Sangid

The Summer Undergraduate Research Fellowship (SURF) Symposium

In the process of machining materials, stresses, called residual stresses, accumulate in the workpiece being machined that remain after the process is completed. These residual stresses can affect the properties of the material or cause part distortion, and it is important that they be calculated to prevent complications from arising due to the residual stresses. However, these calculations can be incredibly computationally intensive, and thus other methods are needed to predict the residual stresses in materials for quick decision-making during machining. By using metamodels - a method of representing data where few data points exist - we can achieve an accurate prediction ...

Mechanical Investigation Of Phase-Transforming Cellular And Origami Materials, John M. Cleveland, David Restrepo, Yunlan Zhang, Pablo Zavattieri, Nilesh Mankame

The Summer Undergraduate Research Fellowship (SURF) Symposium

Cellular materials, such as honeycombs and metallic foams, have attracted much attention due to their exceptional ability to absorb and diffuse mechanical energy. These materials have a wide range of applications, such as improving vehicle crash safety and helmet impact resistance. However, many of these materials are rendered unusable after one application. Phase-transforming cellular materials (PXCMs) utilize a reversible bistable mechanism to facilitate energy absorption from one-dimensional impacts and loads. These mechanisms have the added benefit over other cell structures of reusability. In this study, various PXCM designs are discussed and examined to determine their energy absorption capabilities.

Three different ...

Characterization Of Suspension Polymerized Polyacrylamide And Poly(Sodium Acrylate-Acrylamide) Copolymer And Their Size Influence On The Properties Of Concrete, Cole R. Davis, Kendra A. Erk, Stacey L. Kelly

The Summer Undergraduate Research Fellowship (SURF) Symposium

Shrinkage leading to cracking and mechanical instability is a major problem for concrete due to the loss of water during the curing process. However, through the addition of Superabsorbent Polymer (SAP) hydrogels, shrinkage can be prevented, increasing the strength of concrete. Characterization of suspension polymerized polyacrylamide (PAM) poly(sodium acrylate-polyacrylamide) (PANa-PAM) copolymer microsphere sizes, morphology and swelling behavior was conducted before adding them to concrete. Size was determined using microscopy paired with ImageJ analysis. Coulter Counter size characterization was also used to determine the particle size distribution. Swelling behavior was determined using the tea bag method as well as size ...

Progress Of Carbonation In Chloride Contaminated Concretes, Yaocheng Wang, P. A.M. Basheer, S. Nanukuttan, Y. Bai

International Conference on Durability of Concrete Structures

Concretes used in marine environment are generally under the cyclic effect of CO₂ and chloride ions (Cl^-). To date, the influence of carbonation on ingress of chloride ions in concretes has been widely studied; in comparison, study on the influence of Cl^- on the progress of carbonation is limited. During the study, concretes were exposed to independent and combined mechanisms of carbonation and chloride ingress regimes. Profiles of apparent pH and chloride concentration were used to indicate the progress of carbonation and ingress of Cl^- in concretes. From the apparent pH profile, a carbonation front and a carbonation boundary ...

Corrosion Of Steel In Concrete And Its Prevention In Aggressive Chloride-Bearing Environments, Luca Bertolini, Maddalena Carsana, Matteo Gastaldi, Federica Lollini, Elena Redaelli

International Conference on Durability of Concrete Structures

This keynote paper deals with the durability of reinforced concrete (RC) structures exposed to aggressive environments characterized by high concentration of chloride ions, namely, marine environments or the use of de-icing salts. The mechanism of chloride-induced corrosion of steel in concrete is introduced, and its influence on the service life of RC structures is analyzed. Factors affecting the time to corrosion initiation are described with regard to both concrete properties and environmental exposure conditions. Design approaches available for achieving durability targets associated with the design service life are analyzed, focusing on studies carried out by the authors in recent years ...

Solution Casting And Mechanical Testing Of Arabinan-Cellulose Nanocomposites, Kevin Su, Alina Lusebrink

Materials Engineering

The purpose of this work was to investigate methods to produce consistent, reliable, and testable thin films of arabinan-cellulose nanocomposites. Mechanical properties and composition of the Opuntia ficus-indica cactus spines served as motivation for this research. The high specific strength and stiffness, biodegradability, and sustainability of these spines inspired the creation of composites fabricated from the same materials found in cactus spines: arabinan and nanocrystalline cellulose (NCC). Arabinan serves as the matrix material and NCC as the reinforcement. To explore the feasibility of using a non-toxic solvent, different solution casting techniques with water as a solvent were investigated. Ultrasonication was ...

Predicting Flexural Strength Of Composite Honeycomb Core Sandwich Panels Using Mechanical Models Of Face Sheet Compressive Strength, Nicholas Bruffey, William Shiu

Materials Engineering

The design process at Zodiac Aerospace requires the ability to accurately predict the strength of a composite honeycomb core sandwich panel to adhere to strict FAA regulations. The most common failure mode in long beam composites is in compression. Following ASTM D7249 for a four-point bend test of a long beam flexural test, a mechanical model has been developed that relates the compressive strength of glass fiber face sheets to the flexural strength of the sandwich panel. Zodiac does not currently have data on the compressive strength of the face sheets, so testing was performed to find this property. Asymmetric ...

Buckling Strength In Carbon Fiber Polymer Matrix Composites Produced By Filament Winding For Structural Use In Rockets, Kyle Rosenow

Materials Engineering

High-powered rockets use thin walled carbon-fiber reinforced polymer (CFRP) tubes as the primary structure and the tubes experience compressive stress during flight, which is estimated at 18MPa. Cal Poly Space Systems (CPSS) recently acquired the capability to use filament winding for manufacturing CFRP structures. Filament winding wraps carbon-fiber tow coated in epoxy around an axisymmetric object, and in this case, an aluminum cylinder. The tube laminate is an angle-ply orientation testing the winding angles 35°, 50°, 65°, and 80° and winding patterns 1/1 and 8/1 in combination using an unsupported parallel compression test. Coupons are one-inch in height ...

Finite Element Modeling Of Delamination Damage In Carbon Fiber Laminates Subject To Low-Velocity Impact And Comparison With Experimental Impact Tests Using Nondestructive Vibrothermography Evaluation, George Rodriguez Iv

Master's Theses and Project Reports

Carbon fiber reinforced composites are utilized in many design applications where high strength, low weight, and/or high stiffness are required. While composite materials can provide high strength and stiffness-to-weight ratios, they are also more complicated to analyze due to their inhomogeneous nature. One important failure mode of composite structures is delamination. This failure mode is common when composite laminates are subject to impact loading.

Various finite element methods for analyzing delamination exist. In this research, a modeling strategy based on contact tiebreak definitions in LS-DYNA^®was used. A finite element model of a low-velocity impact event was created to ...

Stress Singularity Study Of Functionally Graded Material Based On Coherent Gradient Sensing Method, Jinjun Zhang

Kevin Lee

Modeling And Experimental Investigation On The Influence Of Radiation Defects On Helium Behavior In Bcc Iron, Zuya Huang

Masters Theses

Fe-based alloys are important structural materials for both fission and fusion energy. For fusion applications, the challenges of radiation-induced changes in microstructure, properties and performance is further challenged by the concomitant production of helium from (n, alpha) nuclear reactions and fusion reactions. Due to the lack of a volumetric, high flux 14-MeV neutron source, studying these phenomena require the use of computational materials modeling and novel experimental methods. In this thesis, molecular dynamics (MD) simulations was used to investigate the synergistic interactions of helium with prismatic dislocation loops characteristic of those observed in neutron irradiated iron to determine how the ...

Measuring Relative Humidity In Concrete Pavements As A Method To Assess Asr Mitigation Measures, Remington G. Reed

Civil Engineering Undergraduate Honors Theses

Alkali-silica reaction (ASR) in concrete is partly facilitated by available moisture within the concrete. In order to better understand this facilitation and to develop processes for ASR mitigation methods, it is necessary to establish a means of monitoring internal relative humidity (RH) within the concrete. Current procedures for measuring RH are time consuming; requiring several hours of equilibration time and specific external conditions to yield accurate results. In order to better understand RH monitoring, laboratory tests were conducted using commercially available RH probes and different controlled environments. Probes were carefully monitored and calibrated in controlled environments, and laboratory tests on ...

Creation And Implementation Of An Underwater-Capable Vr Headset Through The Use Of Additive Manufacturing, Matthew D. Meyers, Nathan Sonnenfeld

Human Factors and Applied Psychology Student Conference

No abstract provided.

Optimizing Chemical & Rheological Properties Of Rejuvenated Bitumen, Dominic Nguyen, Hamzeh Haghshenas Fatmehsari, Santosh Kommidi, Yong-Rak Kim

Civil Engineering Theses, Dissertations, and Student Research

Bitumen has long been a material used in the construction of roadways, yet new pavement only consists of low fractions of recycled materials due to poor compatibility of aged bitumen and new materials. Thus, rejuvenators, chemical additives, have been used in an attempt to re-balance the chemical composition and restore the physical properties of aged bitumen back to its virgin state. A fundamental understanding of how one particular rejuvenator, soybean oil, revitalizes bitumen was investigated using a multi-scale approach.

Fourier-transform infrared spectroscopy (FTIR) was used to determine the changes in chemical properties of pure and rejuvenated virgin and aged samples ...

Koh Etching Of (100) Si Wafer, No 1, Inayat Bajwa

Protocols and Reports

No abstract provided.