SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS
A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 44, ISSUE 13 - JULY 5, 2006
24 COMPOSITE MATERIALS
Includes physical, chemical, and mechanical properties of laminates and other composite materials.
20060016465 Purdue Univ., West Lafayette, IN USA
Composites Reinforced with Short Wavy Fibers
Sun, C T; Cho, J; Deo, A; Mar 1, 2006; 30 pp.; In English Contract(s)/Grant(s): F49620-02-1-0018 Report No.(s): AD-A443834; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA443834; Avail.: CASI: A03, Hardcopy
In short fiber composites including nanocomposites, the load transfer efficiency among fibers is crucial in effecting superior composite properties. It is conceivable that this load transfer efficiency depends on the shape, aspect ratio, and surface area of the fiber. The effect of surface area of the reinforcing element is of particular importance because of the increasing use of nanoparticles in nanocomposites. It is well known that for the some volume, a material at nanoscale possesses much greater surface areas than at larger scales. It is evident that more surface areas mean more load transfer paths and, thus, lower interfacial stresses between the reinforcement and the matrix. The lowering of interfacial stresses is expected to lead to higher composite strengths.
In this research project we used model composites to reach the following conclusions: 1) Wavy fibers lower the interfacial stresses and thus increase the composite strength significantly; 2) for the same fiber volume fraction, the composite with thinner fibers has higher strength than the composite with thicker fibers, 3) result of fiber (platelet) pull-out tests indicates that thinner fibers gave a higher pull out strength than thicker fibers. The increase was about 30% for each 50% reduction in the thickness of the fiber, 4) the Young's modulus of a particulate composite is not influenced by the size of the particle if it is of micron or larger sizes. However, the composite Young's modulus is enhanced with decreasing particle sizes at nano scale. This behavior was explained by using molecular dynamics simulations which revealed that this enhancement of modulus by anoparticles may be attributed to a stiffer polymer layer formed around nanoparticles. DTIC
Composite Materials; Fiber Composites; Molecular Dynamics
20060016580 Collier Research and Development Corp., Hampton, VA USA
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Consistent Structural Integrity and Efficient Certification with Analysis. Volume 3: Appendices of Verification and Validation Examples, Correlation Factors, and Failure Criteria
Collier, Craig; May 2005; 300 pp.; In English Contract(s)/Grant(s): F33615-02-C-3216; Proj-A01V Report No.(s): AD-A444085; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA444085; Avail.: CASI: A13, Hardcopy
This SBIR report maintains that reliable pretest predictions and efficient certification are suffering from inconsistent structural integrity that is prevalent throughout a project's design maturity. Eight primary inconsistencies practiced in aerospace structural analysis are identified.
This SBIR proposes solutions for these inconsistencies and documents software implementation and real-world examples.
Volume 3 provides a collection of verification and validation examples, mostly for composite laminate strength and bonded joints. DTIC
Certification; Composite Materials; Failure; Structural Failure
20060016592 Blue Road Research, Gresham, OR USA
Failure Mechanisms of Fiber Optic Sensors Placed in Composite Materials
Udd, Eric; Winz, Mike; Kreger, Stephen; Heider, Dirk; Jan 2005; 9 pp.; In English; Original contains color illustrations Contract(s)/Grant(s): F49620-03-C-0005 Report No.(s): AD-A444111; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA444111; Avail.: CASI: A02, Hardcopy
This paper provides an overview of considerations associated with placement and operation of fiber optic sensors placed in composite materials. Issues that are discussed include coatings placed on optical fibers and their relationship to the composite structure orientation of optical fibers in the composite parts, methods of providing strain relief, and terminations.Examples are given associated with a series of examples from aerospace and civil structure applications. DTIC
Composite Materials; Failure; Fiber Optics; Optical Measuring Instruments
20060016683 Army Research Lab., Aberdeen Proving Ground, MD USA
Processing and Ballistic Performance of Al2O3/TiB2 Composites
Gilde, Gary A; Adams, Jane W; Sep 2005; 20 pp.; In English; Original contains color illustrations Report No.(s): AD-A444281; ARL-TR-3658; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA444281; Avail.: CASI: A03, Hardcopy
Early research on Al2O3/TiB2 composites focused on exploiting their potential as a low-cost armor ceramic. Limited ballistic data indicated that the microstructure had a dramatic effect on ballistic performance. In some cases, the penetration resistance of Al2O3/TiB2 approached that of monolithic TiB2 ceramics. However, challenges were encountered both in quantifying the microstructural details and fabricating the desired microstructure. The large spread in depth of penetration results for these ceramics, coupled with an insufficient number of samples tested, led to some confusion in accessing the effect microstructure had on the ballistic performance. Our research focused on microstructure control during fabrication and a more thorough ballistic evaluation to correlate microstructure with penetration resistance. Composites were made from mixed Al2O3 and TiB2 powders. The composites, prepared with dramatically different microstructures, had similar ballistic performance. Results show that the penetration resistance of Al2O3/TiB2 composites is not as good as a hot-pressed silicon carbide. DTIC
Aluminum Oxides; Ballistics; Ceramics; Composite Materials; Titanium Borides
20060016732 Naval Surface Warfare Center, Bethesda, MD USA
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Structural Irregularity and Damage Evaluation Routine (SIDER) for Testing of the 1/2-Scale Corvette Hull Section Subjected to UNDEX Testing
Ratcliffe, Colin P; Crane, Roger M; Oct 2005; 33 pp.; In English; Original contains color illustrations Contract(s)/Grant(s): Proj-RTP-US-GE-N-95-002 Report No.(s): AD-A444357; NSWCCD-65-TR-2005/24; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA444357; Avail.: CASI: A03, Hardcopy
This effort entailed performing Structural Irregularity and Damage Evaluation Routine (SIDER) inspection of the entire GRP Hull of a 1/2-scale corvette mid-ship section after each of three underwater explosion (UNDEX) loadings. The SIDERtesting was being used to rapidly interrogate the entire hull structure to identify the areas that had experienced structural degradation that manifested itself in a structural stiffness change. These SIDER results were then compared with the results from a conventional ultrasonic inspection. SIDER is currently being evaluated as a precursor to a rapid conventional non-destructive evaluation (NDE) of large composite structures. The corvette hull provided a platform to determine where conventional NDE inspectors should concentrate their inspections. SIDER was able to identify changes for the entire structure in approximately five hours from beginning (setting up equipment) to end (having plots of where the changes occurred on a planform of the hull). By comparison, conventional ultrasonic inspection of about 1/4 of the starboard side of the hull required approximately 2 days. The coordination of a preinspection using SIDER to guide where conventional techniques should concentrate their effort would reduce overall inspection time and cost. DTIC
Composite Structures; Damage Assessment; Hulls (Structures); Underwater Explosions
20060017017 NASA Langley Research Center, Hampton, VA, USA
Comparison of Damage Path Predictions for Composite Laminates by Explicit and Standard Finite Element Analysis Tools
Bogert, Philip B.; Satyanarayana, Arunkumar; Chunchu, Prasad B.; 2006; 28 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 illustrations Contract(s)/Grant(s): 759-07-11; Copyright; Avail.: CASI: A03, Hardcopy
Splitting, ultimate failure load and the damage path in center notched composite specimens subjected to in-plane tension loading are predicted using progressive failure analysis methodology. A 2-D Hashin-Rotem failure criterion is used in determining intra-laminar fiber and matrix failures. This progressive failure methodology has been implemented in the Abaqus/Explicit and Abaqus/Standard finite element codes through user written subroutines 'VUMAT' and 'USDFLD' respectively. A 2-D finite element model is used for predicting the intra-laminar damages. Analysis results obtained from the Abaqus/Explicit and Abaqus/Standard code show good agreement with experimental results. The importance of modeling delamination in progressive failure analysis methodology is recognized for future studies. The use of an explicit integrationdynamics code for simple specimen geometry and static loading establishes a foundation for future analyses where complex loading and nonlinear dynamic interactions of damage and structure will necessitate it. Author
Laminates; Failure Analysis; Damage; Two Dimensional Models; Mathematical Models; Finite Element Method; Loads (Forces); Predictions
20060017034 NASA Glenn Research Center, Cleveland, OH, USA
Solvent Free Low-Melt Viscosity Imide Oligomers And Thermosetting Polyimide Composites
Chuang, CHun-Hua, Inventor; March 21, 2006; 7 pp.; In English; Original contains black and white illustrations Patent Info.: Filed 23 Jul. 2004; US-Patent-7,015,304; US-Patent-Appl-SN-897279; NASA-Case-LEW-17618-1; No Copyright; Avail.: CASI: A02, Hardcopy
This invention relates to the composition and a solvent-free process for preparing novel imide oligomers and polymers specifically formulated with effective amounts of a dianhydride such as 2,3,3',4-biphenyltetra carboxylic dianydride (a-BPDA), at least one aromatic diamine' and an endcapped of 4-phenylethynylphthalic anhydride (PEPA) or nadic anhydride to produce imide oligomers that possess a low-melt viscosity of 1-60 poise at 260-280' C. When the imide oligomer melt is cured at about 371 C. in a press or autoclave under 100-500 psi, the melt resulted in a thermoset polyimide having a glass transition temperature (T(sub g)) equal to and above 310 C. A novel feature of this process is that the monomers; namely the dianhydrides, diamines and the endcaps, are melt processable to form imide oligomers at temperatures ranging between 232-280 C. (450-535 F) without any solvent. These low-melt imide oligomers can be easily processed by resin transfer molding (RTM), vacuum-assisted resin transfer molding (VARTM) or the resin infusion process with fiber preforms e.g. carbon, glass or quartz preforms to produce polyimide matrix composites with 288-343C (550-650 F) high temperature performance capability. Official Gazette of the U.S. Patent and Trademark Office
Glass Transition Temperature; Anhydrides; Carboxylic Acids; Viscosity; Resin Transfer Molding; Polyimides; Oligomers; High Temperature
20060017063 NASA Johnson Space Center, Houston, TX, USA
Thermal Performance Of Space Suit Elements With Aerogel Insulation For Moon And Mars Exploration
Tang, Henry H.; Orndoff, Evelyne S.; Trevino, Luis A.; January 2006; 8 pp.; In English; 2006 ICES, 17-20 Jul. 2006, Norfolk, VA, USA; Original contains color illustrations Report No.(s): SAE-06ICES-236; Copyright; Avail.: Other Sources
Flexible fiber-reinforced aerogel composites were studied for use as insulation materials of a future space suit for Moon and Mars exploration. High flexibility and good thermal insulation properties of fiber-reinforced silica aerogel composites at both high and low vacuum conditions make it a promising insulation candidate for the space suit application. This paper first presents the results of a durability (mechanical cycling) study of these aerogels composites in the context of retaining their thermal performance. The study shows that some of these Aerogels materials retained most of their insulation performance after up to 250,000 cycles of mechanical flex cycling. This paper also examines the problem of integrating these flexible aerogel composites into the current space suit elements. Thermal conductivity evaluations are proposed for different types of aerogels space suit elements to identify the lay-up concept that may have the best overall thermal performance for both Moon and Mars environments. Potential solutions in mitigating the silica dusting issue related to the application of these aerogels materials for the space suit elements are also discussed. Author
Aerogels; Mars Exploration; Moon; Space Suits; Thermal Conductivity; Thermal Insulation
20060017506 Kanazawa Inst. of Tech., Ishikawa, Japan
Long-Term Durability and Damage Tolerance of Innovative Marine Composites. Part 1. Accelerated Testing for Long-Term Durability of Innovative CFRP Laminates for Marine Use
Miyano, Yasushi; Kimpara, Isao; Feb 14, 2006; 23 pp.; In English; Original contains color illustrations Contract(s)/Grant(s): N00014-01-1-0949 Report No.(s): AD-A444900; KIT-MSRL-06-01; No Copyright; Avail.: CASI: A03, Hardcopy
The prediction of long-term fatigue life of innovative CFRP laminates for marine use under temperature and water environments were performed by our developed * accelerated testing methodology based on the time-temperature superposition principle. Furthermore, Mode I and Mode II interlaminar fracture toughness and the crack growth property underfatigue, thermal and water environments of innovative CFRP laminates were investigated. DTIC
Accelerated Life Tests; Composite Materials; Damage; Durability; Fiber Composites; Laminates; Polymer Matrix Composites; Service Life; Tolerances (Mechanics)
20060018370 Michigan State Univ., MI, USA
Graphite Nanoreinforcements for Aerospace Nanocomposites
Drzal, Lawrence T.; October 25, 2005; 60 pp.; In English; Original contains color illustrations Contract(s)/Grant(s): NAG1-01004; 259-02-07-07; No Copyright; Avail.: CASI: A04, Hardcopy
New advances in the reinforcement of polymer matrix composite materials are critical for advancement of the aerospace industry. Reinforcements are required to have good mechanical and thermal properties, large aspect ratio, excellent adhesion to the matrix, and cost effectiveness. To fulfill the requirements, nanocomposites in which the matrix is filled with nanoscopic reinforcing phases having dimensions typically in the range of 1nm to 100 nm show considerably higher strength and modulus with far lower reinforcement content than their conventional counterparts. Graphite is a layered material whose layers have dimensions in the nanometer range and are held together by weak Van der Waals forces. Once these layers are exfoliated and dispersed in a polymer matrix as nano platelets, they have large aspect ratios. Graphite has an elastic modulus that is equal to the stiffest carbon fiber and 10-15 times that of other inorganic reinforcements, and it is also electrically and thermally conductive. If the appropriate surface treatment can be found for graphite, its exfoliation and dispersion in a polymer matrix will result in a composite with excellent mechanical properties, superior thermal stability, and very good electrical and thermal properties at very low reinforcement loadings. Author
Graphite; Carbon Fibers; Mechanical Properties; Nanocomposites; Polymer Matrix Composites; Thermodynamic Properties; Thermal Stability; Adhesion; Electrical Properties
20060018483 Cambridge Univ., Cambridge, UK
Dynamic Deformation Properties of Energetic Composite Materials
Field, J E; Proud, W G; Siviour, C R; Walley, S M; Grantham, S G; Williamson, D M; Czerski, H; Apr 2005; 164 pp.; In English; Original contains color illustrations Contract(s)/Grant(s): FA8655-03-1-3063 Report No.(s): AD-A445305; SP 1154; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA445305; Avail.: CASI: A08, Hardcopy
This final report consists of six chapters: (1) An introduction to the PCS Fracture and Shock Physics Group (PCS FSP) and some preliminary experiments on PBXs (pp. 3-46); (2) The effect of particle size and temperature on the high strain rate properties of an AP/HTPB PBX (pp. 47-55); (3) Developments in Hopkinson bar instrumentation (pp. 56-74); (4) Visits of Clive R. Siviour to Eglin Airforce Base and studies of impact-induced solid-state phase change in HMX (pp. 75-77); (5) High rate mechanical properties of PBXs (pp. 78-102); (6) Optical techniques (pp. 103-160). Also in Appendix 2 there is a list of the papers published by the PCS FSP Group (and one report from Eglin AFB) during the duration of this contract (2003-2005). Most of these documents are available in PDF format. DTIC
Composite Materials; Deformation; Dynamic Characteristics; Explosives
20060018760 North Carolina State Univ., Raleigh, NC USA
Estimation and Control Related Issues in Smart Material Structures and Fluids
Banks, H T; Pinter, Gabriella A; Potter, Laura K; Munoz, B C; Yanyo, L C; Jul 1998; 18 pp.; In English Contract(s)/Grant(s): F49620-95-1-0236; F49620-95-1-0375 Report No.(s): AD-A445558; No Copyright; Avail.: CASI: A03, Hardcopy
We discuss issues related to modeling of nonlinearities and hysteresis arising in a class of magnetorheological-based smart elastomers. The dynamic models intended for use in parameter estimation and control problems are presented in the context of simple elongation of a filled rubber-line rod. Theoretical computational and experimental results are given. DTIC
Composite Materials; Elastomers; Fluids; Smart Materials
20060018822 North Carolina State Univ., Raleigh, NC USA
On the Radio-Frequency Inputs in Dipolar Heating of Adhesives
Banks, H T; Durso, S R; Goodhart, M A; Joyner, M L; Mar 19, 1999; 24 pp.; In English Contract(s)/Grant(s): F49620-95-1-0236; F49620-95-1-0375 Report No.(s): AD-A445752; No Copyright; Avail.: Defense Technical Information Center (DTIC)
We consider the form of the radio-frequency (RF) or dielectric input expression in the heat equation which arises in the modeling of the curing of epoxy adhesives in bonding of composites.We review two standard derivations of a commonly used expression for the RF heating source term. In this context we discuss difficulties involving the associated inherent polarization assumption and asymptotic behavior of dielectric parameters as a function of the frequency of the RF signal. These difficulties cast doubt on the validity of the standard RF expression. We the use two standard polarization models (Debye and Lorentz) to demonstrate how one can systematically derive general RF heating expressions which do not suffer the inconsistencies that arise in the standard RF expression. DTIC
Adhesives; Composite Materials; Dielectrics; Heating; Radio Frequencies
20060018856 Delaware Univ., Newark, DE USA
Advanced Materials Intelligent Processing Center (AMIPC): Manufacturing for Multi-Functionality
Gillespie, Jr , John W; Advani, Suresh G; Dec 31, 2005; 58 pp.; In English; Original contains color illustrations Contract(s)/Grant(s): N00014-04-1-0574 Report No.(s): AD-A445819; No Copyright; Avail.: CASI: A04, Hardcopy
The work performed by the University of Delaware Center for Composite Materials builds on previous ONR-funded phases of the Advanced Materials Intelligent Processing Center (AMIPC). This work continues the establishment of 21st Century manufacturing practices using intelligent processing to accelerate the insertion of composites into ship applications. Quality, repeatability, tolerances, and affordability can be improved through computer simulations and process design tools as well as automation, combining advanced sensors and process control. The overall goal is to develop and use sensors, science-based simulations, and process control to advance composite manufacturing with Liquid Composite Molding Processes. Advanced sensors have been developed and validated in a manufacturing environment. Simulations incorporate resin ipregnation and cure physics occurring at micro, meso, and macro levels during manufacturing. Passive and active feedback control strategies have been formulated to improve process control. Automation of the process to reduce labor and improve yield has been attempted. Technology transfer has been accelerated by creating user-friendly software and hardware interfaces to implement the methodology on the manufacturing platform. DTIC
Composite Materials; Manufacturing; Resin Transfer Molding; Vacuum
20060019049 Multidisciplinary Center for Earthquake Engineering Research, Buffalo, NY, USA, Cornell Univ., Ithaca, NY, USA
Development of Seismic Strengthening and Retrofit Strategies for Critical Facilities Using Engineered Cementitious Composite Materials
Kesner, K.; Billington, S. L.; Aug. 29, 2005; 232 pp.; In English Contract(s)/Grant(s): NSF-EEC-9701471 Report No.(s): PB2006-111701; MCEER-05-0007; Copyright; Avail.: National Technical Information Service (NTIS)
The research presented herein describes the development of a seismic retrofit system for critical facilities that uses engineered cementitious composite (ECC) materials in lieu of traditional materials. Specifically an infill panel system was developed that utilizes the pseudo-strain hardening properties of the ECC materials. The research consisted of a combinationof laboratory and numerical studies. The infill panel system, which consists of precast ECC panels with bolted connections, was developed for use as a retrofit strategy in critical facilities. Based upon finite-element simulations, a beam-type infill system was found to be effective in increasing the strength, stiffness and energy dissipation of a steel frame without yielding of the bare frame at drift levels up to 0.75%. Structural-scale laboratory tests were used to test the strength of the proposed bolted connections between panel members, and to evaluate the response of ECC infill panels made with various ECC materials, reinforcements and panel geometries. The connection tests results showed the viability of the pretensioned bolted connections. The panel test results indicated the different levels of panel strength, stiffness and energy dissipation that can be achieved. These results serve as benchmark studies for further development of the infill system. To examine the infill panelconcept further, additional simulations were performed using a material model for the ECC developed from reversed cyclic tests. The simulations demonstrated the ability of the proposed ECC infill system to strengthen, stiffen and increase the energy dissipation of steel frames, without causing damage in the frames. NTIS
Cements; Composite Materials
Source: NASA
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