Structures and Materials Commons^™

Thermomechanical Properties And Stress Analysis Of 3-D Textile Composites By Asymptotic Expansion Homogenization Method, Muhammad Ridlo Erdata Nasution, Naoyuki Watanabe, Atsushi Kondo, Arief Yudhanto

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper formulates asymptotic expansion homogenization method for the analysis of 3-D composites whereby thermomechanical effects are considered. The equivalent thermomechanical properties, viz. elastic constants and coefficient of thermal expansion, of 3-D orthogonal interlock composites are obtained based on a unit-cell derived from the optical microscopy observation. The Young's modulus and Poisson's ratio obtained from the analysis are compared with those obtained by experiments. The results show a good agreement especially for the Young's modulus. Localization analysis based on the present formulation is also presented to assess the stresses within the constituents of 3-D composites (fiber tows and resin region) …

Precipitation, Orientation And Composition Effects On The Shape Memory Properties Of High Strength Nitihfpd Alloys, Emre Acar

Theses and Dissertations--Mechanical and Aerospace Engineering

NiTiHf high temperature shape memory alloys are attractive due to their high operating temperatures (>100 ^oC) and acceptable transformation strain compared to NiTi. However, NiTiHf has limitations due to their lack of ductility and low strength, resulting in poor shape memory properties. In this study, Pd has been added to NiTiHf alloys in an attempt to improve their shape memory behavior. A combined approach of quaternary alloying and precipitation strengthening was used.

The characterization of a Ni_45.3Ti_29.7Hf₂₀Pd₅ (at. %) polycrystalline alloy was performed in compression after selected aging treatments. Transmission electron …

A Design Pathfinder With Material Correlation Points For Inflatable Systems, Jared T. Fulcher

Theses and Dissertations--Mechanical and Aerospace Engineering

The incorporation of inflatable structures into aerospace systems can produce significant advantages in stowed volume to mechanical effectiveness and overall weight. Many applications of these ultra-lightweight systems are designed to precisely control internal or external surfaces, or both, to achieve desired performance. The modeling of these structures becomes complex due to the material nonlinearities inherent to the majority of construction materials used in inflatable structures. Furthermore, accurately modeling the response and behavior of the interfacing boundaries that are common to many inflatable systems will lead to better understanding of the entire class of structures. The research presented involved using nonlinear …

Multidimensional Modeling Of Pyrolysis Gas Transport Inside Orthotropic Charring Ablators, Haoyue Weng

Theses and Dissertations--Mechanical and Aerospace Engineering

During hypersonic atmospheric entry, spacecraft are exposed to enormous aerodynamic heat. To prevent the payload from overheating, charring ablative materials are favored to be applied as the heat shield at the exposing surface of the vehicle. Accurate modeling not only prevents mission failures, but also helps reduce cost. Existing models were mostly limited to one-dimensional and discrepancies were shown against measured experiments and flight-data. To help improve the models and analyze the charring ablation problems, a multidimensional material response module is developed, based on a finite volume method framework. The developed computer program is verified through a series of test-cases, …

Buckling, Postbuckling And Imperfection Sensitivity Analysis Of Different Type Of Cylindrical Shells By Hui's Postbuckling Method, Hailan Xu

LSU New Orleans Theses and Dissertations

Hui and Chen (1986) were the first to show that the well-known Koiter’s General Theory of Elastic Stability of 1945 can be significantly improved by evaluating the postbuckling b coefficient at the actual applied load, rather than at the classical buckling load. Such improvement method was demonstrated to be (1) very simple to apply with no tedious algebra, (2) significant reduction in imperfection sensitivity and (3) although it is still asymptotically valid, there exists a significant extension of the range of validity involving larger imperfection amplitudes. Strictly speaking, Koiter’s theory of 1945 is valid only for vanishingly small imperfection amplitudes. …

Molecular Dynamics Model Of Carbon Nanotubes In Epon 862/Detda Polymer, Guttormur Arnar Ingvason

Doctoral Dissertations and Master's Theses

The aerospace industry is interested in increasing the strength while reducing the weight of carbon fiber composite materials. Adding single walled carbon nanotubes (SWCNT) to a polymer matrix can achieve that goal by improving delamination properties of the composite. Due to the complexity of polymer molecules and the curing process, few 3-D Molecular Dynamics simulations of a polymer-SWCNT composite have been run. Our model runs on the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS), with a COMPASS (Condensed phase Optimized Molecular Potential for Atomistic Simulations Studies) potential to represent the interactions between the atoms of the polymer and the SWCNT. This …

Mode I Fracture Toughness Of Eight-Harness-Satin Carbon Cloth Weaves For Co-Cured And Post-Bonded Laminates, Josh E. Smith

Master's Theses

Mode I interlaminar fracture of 3k 8-Harness-Satin Carbon cloth, with identical fill and weft yarns, pre-impregnated with Newport 307 resin was investigated through the DCB test (ASTM D5528). Crack propagations along both the fill and weft yarns were considered for both post-bonded (co-bonded) and co-cured laminates. A patent-pending delamination insertion method was compared to the standard Teflon film option to assess its applicability to mode I fracture testing. The Modified Beam Theory, Compliance Calibration method, and Modified Compliance Calibration method were used for comparative purposes for these investigations and to evaluate the validity of the proposed Equivalent Stiffness (EQS) method. …

Set-Up Of Digital Image Correlation Apparatus, German A. Parada, Michael Sangid

The Summer Undergraduate Research Fellowship (SURF) Symposium

Digital Image Correlation (DIC) is a valuable and customizable experimental technique employed to analyze localized strain regions on materials by tracking the displacement of points on the surface of the studied material under applied stress. To investigate materials behavior, it is vital to correctly set-up the DIC apparatus so work has been done to ready the equipment to start measurements on two distinct projects. On the first project, the fatigue crack behavior of a high-strength aluminum alloy will be studied by cyclic loading, testing necessary for the safe design of aircraft parts utilizing this novel alloy. DIC will be carried …

Validation Of Long-Fiber Thermoplastic Composite Models, Christian A. Vuong, Megan Kinney, Michael Sangid

The Summer Undergraduate Research Fellowship (SURF) Symposium

With increased pressure to reduce energy consumption, long-fiber reinforced thermoplastic composites (LFTs) are of interest to aerospace and automotive industries due to their light weight in combination with other desirable mechanical properties and ease of manufacturing to replace common materials such as aluminum and magnesium. However, the performance of LFTs is highly dependent on microstructural variables such as fiber length and orientation, which are heavily influenced by the manufacturing process. Accurately predicting these factors would allow for more rapid advances in LFTs by reducing the experiments needed for certification and decreasing expenses. While models that serve this purpose exist, the …

Traditional Boat Building: An Intersection Of Zanzibar’S Culture And Environment, Eric Levenson

Independent Study Project (ISP) Collection

This study examined traditional boat building on Uzi Island as a manifestation of Zanzibar’s relationship of environment and culture. Information was gathered about traditional boat building practices, the resource use and management pertaining to boats, the cultural reliance on boats, and local views on environment and conservation. This information showed that the people of Uzi Island were dependent on the use of traditional boats to maintain their livelihood, however the tree types used for boat building are being over-harvested. This tension of culture and environment exposed the need for conservation of Zanzibar’s natural resources in a manner that does not …

Compression Properties And Damage Mechanisms Of Stitched Carbon/Epoxy Composites, Arief Yudhanto, Naoyuki Watanabe, Yutaka Iwahori, Hikaru Hoshi

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The effect of stitching on compression properties and damage mechanisms of carbon/epoxy composites is experimentally investigated. The waviness angle of load-bearing tows is also measured in both in-plane and out-of-plane directions, and a correlation is made between compression strength and the waviness angle. It is found that stitching generally reduces the compression strength of carbon/epoxy composites of up to 16%. The average compression strength has a stronger correlation with the in-plane waviness angle rather than the out-of-plane one. A comparative damage assessment, which studies the initiation, progression and final failure in stitched and unstitched composites under axial compression, reveals that …

The Effects Of Fabrication Methods And Cure Cycle On The Mechanical Properties Of Carbon Fiber Laminate In Tensile And 3-Point Bend Testing, Adriano Agostino

Aerospace Engineering

This project was completed at the California Polytechnic State University, San Luis Obispo Aerospace Engineering Structures and Composites Lab during Spring Quarter 2013. The purpose of this project was to research and to gain insight into the effects of fabrication methods and of modifying cure cycles for Newport NB-301 12l 2x2 Twill Weave Carbon Fiber material properties. The two fabrication methods used were autoclave and heat press (compression molding) methods. Each fabrication method used two cure cycles, a recommended cure cycle of 275°F for 1 hour and a modified cure cycle of 250°F for 1.5 hours. The exact product data …

Study Of Natural Composite Materials Square Beam Under Three Point Bending Test, Casey Wu

Aerospace Engineering

The purpose of this report is to summarize the findings on three point bending tests to try to find the optimum geometrical shape and layup configuration of a square beam composed of natural composites. The final project was entered into the SAMPE 2013 bridge building competition to compete internationally against other universities in the natural square beam category. The main focus of the bridge project is to compose it entirely of natural occurring fibers and other natural materials to create a “green” beam. The beams in the competition are tested under 3 point bending tests and will be scored based …

Global Skin Friction Diagnostics: The Glof Technique And Measurements Of Complex Separated Flows, Sudesh A. Woodiga

Dissertations

This work describes the application of the global luminescent oil film skin friction meter to quantitative global skin friction diagnostics of complex separated flows. The development of this technique is based on the relationship between the oil film thickness and luminescent intensity of a luminescent oil film. The projected thin oil film equation is given to relate the normalized luminescent intensity with skin friction. The variational formulation with a smoothness constraint on skin friction is proposed to obtain a snap shot solution from two consecutive images for a relative skin friction field. A complete skin friction field is reconstructed through …

Design, Fabrication, And Testing Of An Emr Based Orbital Debris Impact Testing Platform, Jeffrey J. Maniglia Jr.

Master's Theses

This paper describes the changes made from Cal Poly’s initial railgun system, the Mk. 1 railgun, to the Mk. 1.1 system, as well as the design, fabrication, and testing of a newer and larger Mk. 2 railgun system. The Mk. 1.1 system is developed as a more efficient alteration of the original Mk. 1 system, but is found to be defective due to hardware deficiencies and failure, as well as unforeseen efficiency losses. A Mk. 2 system is developed and built around donated hardware from the Naval Postgraduate School. The Mk. 2 system strove to implement an efficient, augmented, electromagnetic …

Fatigue Testing And Data Analysis Of Welded Steel Cruciform Joints, Alina Shrestha

LSU New Orleans Theses and Dissertations

In this study, ABS Publication 115, “Guidance on Fatigue Assessment of Offshore Structures” is briefly reviewed. Emphasis is on the S-N curves based fatigue assessment approach of non-tubular joints, and both size and environment effects are also considered. Further, fatigue tests are performed to study the fatigue strength of load-carrying and non-load-carrying steel cruciform joints that represent typical joint types in marine structures. The experimental results are then compared against ABS fatigue assessment methods, based on nominal stress approach, which demonstrates a need for better fatigue evaluation parameter. A good fatigue parameter by definition should be consistent and should correlate …

Analysis And Mitigation Of The Cubesat Dynamic Environment, Steve M. Furger

Master's Theses

A vibration model was developed for CubeSats inside the Poly-Picosatellite Orbital Deployer (P-POD). CubeSats are fixed in the Z axis of deployers, and therefore resonate with deployer peaks. CubeSats generally start fixed in the X and Y axes, and then settle into an isolated position. CubeSats do not resonate with deployers after settling into an isolated position. Experimental data shows that the P-POD amplifies vibration loads when CubeSats are fixed in the deployer, and vibration loads are reduced when the CubeSats settle into an isolated position. A concept for a future deployer was proposed that isolates CubeSats from the deployer …

The Application Of Advanced Composites For The Construction Of Commercial Transport Aircraft, Mark D. Severson

Graduate Student Works

This individual Capstone project examined and evaluated current industry methods of testing, certification, and maintenance of advanced composite materials for the construction of commercial transport aircraft and the FAA regulations governing their use. The project critically compared and contrasted existing FAA standards and regulations governing the testing, certification, and maintenance of advanced composites for commercial transport aircraft structural applications with current industry practices to determine whether there were any areas of conflict between the two in order to accept or reject that current testing, certification, and maintenance procedures for advanced composites used in primary and secondary commercial transport aircraft structures …

Design Of A Specimen Fixture For Impact Resistance Testing In An Instron Dynatup 8250 Drop Weight Impact Tester, Daniel Alejandro Barath

Aerospace Engineering

The purpose of this report is to outline the path and methods used to design a specimen fixture for the testing and analysis of fiber reinforced composites subjected to impact loading. This design is done in support of the California Polytechnic State University in San Luis Obispo Structures and Composites Laboratory. The design request was made at the request of Dr. Eltahry Elghandour to support the graduate students Kodi A. Rider and Y. Vanessa Wood in their master’s degree thesis projects.

The design request involved the design of a specimen fixture compatible with the existing impact apparatus located in the …

Validation Of Proposed Metrics For Two-Body Abrasion Scratch Test Analysis Standards: In Principle, Any Scratch Can Be Analyzed By This Method, Kenneth W. Street, Ryan L. Kobrick, David M. Klaus

Publications

Abrasion of mechanical components and fabrics by soil on Earth is typically minimized by the effects of atmosphere and water. Potentially abrasive particles lose sharp and pointed geometrical features through erosion. In environments where such erosion does not exist, such as the vacuum of the Moon, particles retain sharp geometries associated with fracturing of their parent particles by micrometeorite impacts. The relationship between hardness of the abrasive and that of the material being abraded is well understood, such that the abrasive ability of a material can be estimated as a function of the ratio of the hardness of the two …