SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS
A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 44, ISSUE 12 - JUNE 20, 2006
24 COMPOSITE MATERIALS
Includes physical, chemical, and mechanical properties of laminates and other composite materials.
20060014005 NASA Langley Research Center, Hampton, VA, USA
Micromechanics Modeling of Functionally Graded Interphase Regions in Carbon Nanotube-Polymer Composites
Seidel, Gary D.; Lagoudas, Dimitris C.; Frankland, Sarah Jane V.; Gates, Thomas S.; January 2006; 15 pp.; In English; 47th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 1-4 May 2006, Newport, RI, USA; Original contains color and black and white illustrations Contract(s)/Grant(s): DE-AC04-94AL-85000; NCC1-02038; 759-07-11 Report No.(s): AIAA Paper 2006-1678; Copyright; Avail.: CASI: A03, Hardcopy
The effective elastic properties of a unidirectional carbon fiber/epoxy lamina in which the carbon fibers are coated with single-walled carbon nanotubes are modeled herein through the use of a multi-scale method involving the molecular dynamics/equivalent continuum and micromechanics methods. The specific lamina representative volume element studied consists of a carbon fiber surrounded by a region of epoxy containing a radially varying concentration of carbon nanotubes which is then embedded in the pure epoxy matrix. The variable concentration of carbon nanotubes surrounding the carbon fiber results in a functionally graded interphase region as the properties of the interphase region vary according to the carbon nanotube volume fraction. Molecular dynamics and equivalent continuum methods are used to assess the local effective properties of the carbon nanotube/epoxy comprising the interphase region. Micromechanics in the form of the Mori-Tanaka method are then applied to obtain the global effective properties of the graded interphase region wherein the carbon nanotubes are randomly oriented. Finally, the multi-layer composite cylinders micromechanics approach is used to obtain the effective lamina properties from the lamina representative volume element. It was found that even very small quantities of carbon nanotubes (0.36% of lamina by volume) coating the surface of the carbon fibers in the lamina can have a significant effect (8% increase) on the transverse properties of the lamina (E22, k23, G23 and G12) with almost no affect on the lamina properties in the fiber direction (E11 and v12). Author
Carbon Fibers; Epoxy Matrix Composites; Laminates; Carbon Nanotubes; Fiber Composites; Epoxy Resins; Elastic Properties
20060014151 Maine Univ., Orono, ME USA
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Development of a Cavitation Erosion Resistant Advanced Material System
Kendrick, Light H; Caccese, Vincent; Nov 2005; 76 pp.; In English; Original contains color illustrations Contract(s)/Grant(s): N00014-01-1-0916 Report No.(s): AD-A441468; UM-MACH-RPT-01-05; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA441468; Avail.: CASI: A05, Hardcopy
Advancements in both the design and construction of high-speed naval vessels have necessitated the evaluation of the building materials in a cavitating environment. Given their weight advantages, construction materials are often either aluminum or glass reinforced polymer (GRP) composites. Historically, neither of these materials has performed well in a cavitating environment. The objective of this effort was to evaluate cavitation erosion protection alternatives for a GRP composite structure used in a cavitating environment. Screening of the various design alternatives was done using the ASTM 032 vibratory induced cavitation test method and a relative ranking of each protection system was generated. Results from the testing show that a GRP composite system can be designed to greatly increase the cavitation erosion resistance of the material, but this resistance remains below common metallic materials. A solution identified during this study involves the use of durable elastomer materials as the protection mechanism. DTIC
Cavitation Corrosion; Cavitation Flow; Composite Materials; Corrosion Resistance; Erosion; Reinforcing Materials; Ship Hulls
20060015457 Air Force Research Lab., Edwards AFB, CA USA
Multi-Scale Approach to Investigate the Tensile and Fracture Behavior of Nano Composite Materials
Liu, Chi T; Sep 2005; 15 pp.; In English Contract(s)/Grant(s): Proj-2302 Report No.(s): AD-A443333; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA443333; Avail.: CASI: A03, Hardcopy
This report covers results addressing multi-scale measurements of deformation, strain, and failure behavior in particulate composites containing nano size particles. In addition, techniques are developed, based on multi-scale modeling approaches, to model particles interaction, damage initiation and evolution processes, and constitutive and crack growth behavior in particulate composites. The program's basic approach involves a blend of numerical and experimental studies. The results of these studies are evaluated and discussed. DTIC
Composite Materials; Fracture Mechanics; Tensile Properties
20060015726 Air Force Research Lab., Wright-Patterson AFB, OH USA
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Improving the D2512 Lox Compatibility of Composites by Using Thermally Conductive Graphite Fibers
Gerzeski, Roger; Sep 2005; 302 pp.; In English; Original contains color illustrations Report No.(s): AD-A443342; No Copyright; Avail.: Defense Technical Information Center (DTIC)
This effort demonstrated that using a thermally conductive fiber substantially enhances a composite's ASTM D2512 mechanical impact liquid oxygen compatibility. It repeatedly achieved 90% of the goal of passing D2512 with a 1700% improvement over baseline. This effort also documented the types of fracture surfaces routinely found in the residuals of the materials investigated. These fracture surfaces indicate that hertzian fracture is the mechanism by which a specimen fractured and failed. The fracture surfaces routinely indicated that kinetic friction associated with signs of intense heating occurred. Kinetic friction's mechanical-to-thermal transformation mechanism provided the only phenomenological explanation for the extremely rapid and large temperature rises required for conditions recognizable as ignition to occur in the time frame of a D2512 test. The effort crystallized the sequence from fracture to heating to ignition. First, a series of hertzian fractures develop. These allow kinetic friction of the hertzian fractured material to occur. Kinetic friction transforms mechanical energy into temperature rising thermal energy. This thermal energy causes the material to degrade by radical chain scission and oxidize by radical addition peroside chemistry to a degree detectable as ignition. DTIC
Compatibility; Composite Materials; Fracturing; Graphite; Liquid Oxygen; Residual Stress; Thermal Conductivity
20060015771 Delaware Univ., Newark, DE USA
Numerical and Experimental Studies of Damage Generation in Multi-Layer Composite Materials at High Strain Rates
Hall, I W; Jan 5, 2006; 50 pp.; In English; Original contains color illustrations Report No.(s): AD-A443456; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA443456; Avail.: CASI: A03, Hardcopy
This report concerns the results of a S.T.I.R. Program carried out between March and November 2005. The general objectives of the program were to demonstrate the feasibility and utility of a novel use of the Split Hopkinson Pressure Bar (SHPB) as a tool for the investigation and development of multi-layered materials for high strain rate applications. Here, the SHPB is not used as a device for generating mechanical property data but is, instead, used as a probe to generate input and output signals which are then used to validate numerical models. The principle of the method is to perform an experiment on the SHPB and collect the usual data which accurately define the input wave and the exit waves. Strain gages on the sample itself can provide extra data at specific locations on the sample surface. The numerical model is then developed, based on properties from tests conducted on simple single layer samples. The model comprises the incident and transmitter bars of the SHPB set-up plus the sample: the known incident wave is the model input. Then, when the numerically calculated exit waves exactly match the experimentally determined exit waves the model must be accurately capturing the details of wave propagation, transmission and reflection within the sample itself. This provides the basic validation of the model. DTIC
Composite Materials; Damage; Damage Assessment; Mathematical Models; Strain Rate
20060016033 Washington Univ., Seattle, WA USA
Spark Plasma Sintering (SPS) for Nanostructured Smart Materials
Taya, Minoru; Feb 5, 2006; 35 pp.; In English Contract(s)/Grant(s): FA9550-04-1-0343 Report No.(s): AD-A443838; CIMS-02-2006; No Copyright; Avail.: CASI: A03, Hardcopy
This DURIP project is aimed at establishing a new Spark Plasma Sintering(SPS) equipment by which we will be able to process a new set of nano-structured smart materials and composites; shape memory alloy(SMA) composites, ferromagnetic SMA composites, piezo-composites with and without functionally graded microstructure(FGM), a new active materials such as piezo-SMA composites. These composites will be used for higher performance airborne actuators and smart window materials and energy harvesting and cooling materials for airborne antennas. DTIC
Composite Materials; Ferromagnetic Materials; Nanostructures (Devices); Plasmas (Physics); Shape Memory Alloys; Sintering; Smart Materials; Sparks
20060016042 Illinois Univ. at Urbana-Champaign, Urbana, IL USA
Multiscale Modeling and Experiments for Design of Self-Healing Structural Composite Materials
White, Scott R; Geubelle, Philippe H; Sottos, Nancy R; Aug 2005; 15 pp.; In English Contract(s)/Grant(s): F49620-02-1-0080 Report No.(s): AD-A443864; No Copyright; Avail.: CASI: A03, Hardcopy
A set of multi-scale materials systems design tools focused on issues relevant to self-healing structural composites have been developed by a research team from the University of Illinois and the University of Michigan. Our vision was to create a computational framework for materials systems design spanning from atomistic to macroscopic (structural) length scales, supported and validated by a set of experiments conducted at various scales. Although special emphasis in the present project ha been placed on the modeling of the fatigue response of a self-healing composite, the approach adopted in this project yielded tool that have broad applicability for generic fracture and fatigue problems in modem engineering materials. This paper summarizes our accomplishments of the past three years primarily on the macroscale numerical and experimental aspects of the program. 0 the numerical side, we have focused on the development, implementation and validation of a cohesive failure model able to capture at the structural level the fatigue retardation effect of the healing agent on the cyclic response of the self-healing composite. DTIC
Composite Materials; Healing
20060016325 Army Research Lab., Aberdeen Proving Ground, MD USA
Large-Scale Integrated Process Modeling Simulations Enabling Composite Materiel Development Applications
Henz, Brian J; Shires, Dale R; Dec 2005; 32 pp.; In English; Original contains color illustrations Report No.(s): AD-A443647; ARL-TR-3680; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA443647; Avail.: CASI: A03, Hardcopy
A virtual manufacturing environment that provides modules for predicting the process-inducted residual stresses in polymeric composite materials has recently gone through extensive testing by the authors. The use of polymeric composite materials in Department of Defense materiel developments has made it increasingly important to predict the service life and the mechanical responses of such structures. Process-induced behavior plays a critical role in the accurate modeling of mechanical responses. Predicting process-induced residual stresses of composite material structures requires the coupling of resin infusion, heat transfer, and multiscale thermal residual stress models. The complexity of modeling the process-induced effects requires the use of modern software engineering techniques with multiphysics coupled models. The model and software developmental efforts are described in this report. DTIC
Composite Materials; Composite Structures; Models; Polymers; Residual Stress; Simulation; Virtual Reality
20060016356 NASA Langley Research Center, Hampton, VA, USA
Preparation and Properties of Nanocomposites Prepared From Shortened, Functionalized Single-Walled Carbon Nanotubes
Smith, J. G., Jr.; Delozier, D. M.; Watson, K. A.; Connell, J. W.; Yu, Aiping; Haddon, R. C.; Bekyarova, E.; [2006]; 13 pp.; In English; SAMPE 2006 Symposium and Exhibition (51st ISSE), 30 Apr. - 4 May 2006, Long Beach, CA, USA; Original contains black and white illustrations Contract(s)/Grant(s): 612-20-07-12; No Copyright; Avail.: CASI: A03, Hardcopy
As part of a continuing materials development activity, low color space environmentally stable polymeric materials that possess sufficient electrical conductivity for electrostatic charge dissipation (ESD) have been investigated. One method of incorporating sufficient electrical conductivity for ESD without detrimental effects on other polymer properties of interest (i.e., optical and thermo-optical) is through the incorporation of single-walled carbon nanotubes (SWNTs). However, SWNTs are difficult to fully disperse in the polymer matrix. One means of improving dispersion is by shortening and functionalizing SWNTs. While this improves dispersion, other properties (i.e., electrical) of the SWNTs can be affected which can in turn alter the final nanocomposite properties. Additionally, functionalization of the polymer matrix can also influence nanocomposite properties obtained from shortened, functionalized SWNTs. The preparation and characterization of nanocomposites fabricated from a polyimide, both functionalized and unfunctionalized, and shortened, functionalized SWNTs will be presented. Author
Nanocomposites; Carbon Nanotubes; Spacecraft Construction Materials; Polyimides; Electrical Resistivity; Electrostatic Charge
Source: NASA
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