SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS
A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 44, ISSUE 11 - MAY 30, 2006
24 COMPOSITE MATERIALS
Includes physical, chemical, and mechanical properties of laminates and other composite materials.
20060013319 Kentucky Univ., Lexington, KY USA
Inspection and Evaluation of a Bridge Deck Reinforced with Carbon Fiber Reinforced Polymer (CFRP) Bars
Chiaw, C. C.; Harik, I.; Mar. 2006; 24 pp.; In English Report No.(s): PB2006-110314; KTC-06-06/FRT102-00-1F; No Copyright; Avail.: CASI: A03, Hardcopy
Cracking in reinforced concrete decks is inevitable. It leads to the corrosion and eventual deterioration of the deck system. The use of non-corrosive reinforcement is one alternative to steel in reinforced concrete construction. This report deals with the field evaluation and performance of a concrete bridge deck reinforced with carbon fiber reinforced polymer (CFRP) bars. The bridge is identified as the Elkin Station Road Bridge on route CR1210 over the Two-Mile Creek in Clark County, KY. The CFRP bars were placed in the top and bottom mats of the bridge deck in both the transverse and longitudinal directions. The results of the laboratory tensile tests of the CFRP bars used in the deck are presented in this report. The bridge was opened to traffic in May 2002. Monitoring of crack formation and location, and maximum crack width and length in the deck initiated in June 2002 and continued until September 2005. The cracks in the deck were not measurable since the maximum observed crack width was less than the smallest unit (1/100 inch) on the crack comparator. This indicates that the cracks are well below the maximum allowed crack width of 0.013 inch per AASHTO Standard Specification for exterior exposure. NTIS
Carbon Fiber Reinforced Plastics; Carbon Fibers; Fiber Composites; Crack Propagation; Crack Initiation; Cracks
20060013345 NASA Glenn Research Center, Cleveland, OH, USA
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NASALife-Component Fatigue and Creep Life Prediction Program and Illustrative Examples
Murthy, Pappu L. N.; Mital, Subodh K.; Gyekenyesi, John Z.; [2005]; 6 pp.; In English; International Conference on Computational and Experimental Engineering and Sciences, 1-6 Dec. 2005, Madras, India; Original contains color and black and white illustrations Contract(s)/Grant(s): WBS 22-714-30-20; Copyright; Avail.: CASI: A02, Hardcopy
NASALife is a life prediction program for propulsion system components made of ceramic matrix composites (CMC) under cyclic thermo-mechanical loading and creep rupture conditions. Although, the primary focus was for CMC components the underlying methodologies are equally applicable to other material systems as well. The program references data for low cycle fatigue (LCF), creep rupture, and static material properties as part of the life prediction process. Multiaxial stresses are accommodated by Von Mises based methods and a Walker model is used to address mean stress effects. Varying loads are reduced by the Rainflow counting method. Lastly, damage due to cyclic loading (Miner s rule) and creep are combined to determine the total damage per mission and the number of missions the component can survive before failure are calculated. Illustration of code usage is provided through example problem of a CMC turbine stator vane made of melt-infiltrated, silicon carbide fiber-reinforced, silicon carbide matrix composite (MI SiC/SiC) Derived from text
Prediction Analysis Techniques; Creep Properties; Ceramic Matrix Composites; Propulsion System Configurations; Fatigue Life; Life (Durability); Cyclic Loads
20060013348 NASA Glenn Research Center, Cleveland, OH, USA
Modified Single-Wall Carbon Nanotubes for Reinforce Thermoplastic Polyimide
Lebron-COlon, Marisabel; Meador, Michael A.; [2006]; 8 pp.; In English; SAMPE 2006, 30 Apr. - 4 May 2006, Long Beach, CA, USA; Original contains color and black and white illustrations; No Copyright; Avail.: CASI: A02, Hardcopy
A significant improvement in the mechanical properties of the thermoplastic polyimide film was obtained by the addition of noncovalently functionalized single-wall carbon nanotubes (SWNTs). Polyimide films were reinforced using pristine SWNTs and functionalized SWNTs (F-SWNTs). The tensile strengths of the polyimide films containing F-SWNTs were found to be approximately 1.4 times higher than those prepared from pristine SWNTs. Author
Carbon Nanotubes; Polyimides; Thermoplasticity; Nanocomposites; Reinforcing Materials
20060013414 Ohio Aerospace Inst., Cleveland, OH, USA
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Modeling the Stress Strain Behavior of Woven Ceramic Matrix Composites
Morscher, Gregory N.; January 2006; 31 pp.; In English; 107th Annual American Ceramic Society Conference Richard M. Fulrath Symposium, 10-13 Apr. 2005, Baltimore, MD, USA; Original contains color illustrations Contract(s)/Grant(s): NNC05AA16A; 953033.01.03.33 Report No.(s): E-15518; No Copyright; Avail.: CASI: A03, Hardcopy
Woven SiC fiber reinforced SiC matrix composites represent one of the most mature composite systems to date. Future components fabricated out of these woven ceramic matrix composites are expected to vary in shape, curvature, architecture, and thickness. The design of future components using woven ceramic matrix composites necessitates a modeling approach that can account for these variations which are physically controlled by local constituent contents and architecture. Research over the years supported primarily by NASA Glenn Research Center has led to the development of simple mechanistic-based models that can describe the entire stress-strain curve for composite systems fabricated with chemical vapor infiltrated matrices and melt-infiltrated matrices for a wide range of constituent content and architecture. Several examples will be presented that demonstrate the approach to modeling which incorporates a thorough understanding of the stress-dependent matrix cracking properties of the composite system. Author
Ceramic Matrix Composites; Fiber Composites; Woven Composites; Silicon Carbides; Matrix Materials; Fabrication; Cracking (Fracturing)
20060013416 NASA Glenn Research Center, Cleveland, OH, USA
Compressive Failure of Fiber Composites Under Multi-axial Loading
Basu, Shiladitya; Waas, Anthony M.; Ambur, Damodar R.; Elsevier, Journal of Mechanics and Physics of Solids; January 2006; Vol. 54, 3, pp. 611-634; In English; Original contains black and white illustrations Contract(s)/Grant(s): NCC1-01050; Copyright; Avail.: Other Sources
This paper examines the compressive strength of a fiber reinforced lamina under multi-axial stress states. An equilibrium analysis is carried out in which a kinked band of rotated fibers, described by two angles, is sandwiched between two regions in which the fibers are nominally straight. Proportional multi-axial stress states are examined. The analysis includes the possibility of bifurcation from the current equilibrium state. The compressive strength of the lamina is contingent upon either attaining a load maximum in the equilibrium response or satisfaction of a bifurcation condition, whichever occurs first. The results show that for uniaxial loading a non-zero kink band angle beta produces the minimum limit load. For multi-axial loading, different proportional loading paths show regimes of bifurcation dominated and limit load dominated behavior. The present results are able to capture the beneficial effect of transverse compression in raising the composite compressive strength as observed in experiments. Author
Axial Stress; Compressive Strength; Fiber Composites; Failure Analysis; Loads (Forces); Laminates
20060013424 Ohio Aerospace Inst., Brook Park, OH, USA
Modeling the Elastic Modulus of 2D Woven CVI SiC Composites
Morscher, Gregory N.; [2006]; 28 pp.; In English; Original contains color and black and white illustrations Contract(s)/Grant(s): NNC05AA16A; WBS 033.01.03.33; No Copyright; Avail.: CASI: A03, Hardcopy
The use of fiber, interphase, CVI SiC minicomposites as structural elements for 2D-woven SiC fiber reinforced chemically vapor infiltrated (CVI) SiC matrix composites is demonstrated to be a viable approach to model the elastic modulus of these composite systems when tensile loaded in an orthogonal direction. The 0deg (loading direction) and 90deg (perpendicular to loading direction) oriented minicomposites as well as the open porosity and excess SiC associated with CVI SiC composites were all modeled as parallel elements using simple Rule of Mixtures techniques. Excellent agreement for a variety of 2D woven Hi-Nicalon(TradeMark) fiber-reinforced and Sylramic-iBN reinforced CVI SiC matrix composites that differed in numbers of plies, constituent content, thickness, density, and number of woven tows in either direction (i.e, balanced weaves versus unbalanced weaves) was achieved. It was found that elastic modulus was not only dependent on constituent content, but also the degree to which 90deg minicomposites carried load. This depended on the degree of interaction between 90deg and 0deg minicomposites which was quantified to some extent by composite density. The relationships developed here for elastic modulus only necessitated the knowledge of the fractional contents of fiber, interphase and CVI SiC as well as the tow size and shape. It was concluded that such relationships are fairly robust for orthogonally loaded 2D woven CVI SiC composite system and can be implemented by ceramic matrix composite component modelers and designers for modeling the local stiffness in simple or complex parts fabricated with variable constituent contents. Author
Ceramic Matrix Composites; Woven Composites; Composite Materials; Modulus of Elasticity; Porosity; Loads (Forces); Fabrication
20060013437 NASA Langley Research Center, Hampton, VA, USA
Mechanical Properties of T650-35/AFR-PE-4 at Elevated Temperatures for Lightweight Aeroshell Designs
Whitley, Karen S.; Collins, TImothy J.; [2006]; 13 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): 759-07-11 Report No.(s): AIAA Paper 2006-2202; No Copyright; Avail.: CASI: A03, Hardcopy
Considerable efforts have been underway to develop multidisciplinary technologies for aeroshell structures that will significantly increase the allowable working temperature for the aeroshell components, and enable the system to operate at higher temperatures while sustaining performance and durability. As part of these efforts, high temperature polymer matrix composites and fabrication technologies are being developed for the primary load bearing structure (heat shield) of the spacecraft. New high-temperature resins and composite material manufacturing techniques are available that have the potential to significantly improve current aeroshell design. In order to qualify a polymer matrix composite (PMC) material as a candidate aeroshell structural material, its performance must be evaluated under realistic environments. Thus, verification testing of lightweight PMC's at aeroshell entry temperatures is needed to ensure that they will perform successfully in high-temperature environments. Towards this end, a test program was developed to characterize the mechanical properties of two candidate material systems, T650-35/AFR-PE-4 and T650-35/RP46. The two candidate high-temperature polyimide resins, AFR-PE-4 and RP46, were developed at the Air Force Research Laboratory and NASA Langley Research Center, respectively. This paper presents experimental methods, strength, and stiffness data of the T650-35/AFR-PE-4 material as a function of elevated temperatures. The properties determined during the research test program herein, included tensile strength, tensile stiffness, Poisson s ratio, compressive strength, compressive stiffness, shear modulus, and shear strength. Unidirectional laminates, a cross-ply laminate and two eight-harness satin (8HS)-weave laminates (4-ply and 10-ply) were tested according to ASTM standard methods at room and elevated temperatures (23, 316, and 343 C). All of the relevant test methods and data reduction schemes are outlined along with mechanical data. These data contribute to a database of material properties for high-temperature polyimide composites that will be used to identify the material characteristics of potential candidate materials for aeroshell structure applications. Author
Aeroshells; Mechanical Properties; Aircraft Design; High Temperature; Fabrication; Composite Materials
20060013456 NASA Langley Research Center, Hampton, VA, USA
Variable Stiffness Panel Structural Analyses With Material Nonlinearity and Correlation With Tests
Wu, K. Chauncey; Gurdal, Zafer; [2006]; 20 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): 23-064-30-34 Report No.(s): AIAA Paper 2006-2165; Copyright; Avail.: CASI: A03, Hardcopy
Results from structural analyses of three tow-placed AS4/977-3 composite panels with both geometric and material nonlinearities are presented. Two of the panels have variable stiffness layups where the fiber orientation angle varies as a continuous function of location on the panel planform. One variable stiffness panel has overlapping tow bands of varying thickness, while the other has a theoretically uniform thickness. The third panel has a conventional uniform-thickness [plus or minus 45](sub 5s) layup with straight fibers, providing a baseline for comparing the performance of the variable stiffness panels. Parametric finite element analyses including nonlinear material shear are first compared with material characterization test results for two orthotropic layups. This nonlinear material model is incorporated into structural analysis models of the variable stiffness and baseline panels with applied end shortenings. Measured geometric imperfections and mechanical prestresses, generated by forcing the variable stiffness panels from their cured anticlastic shapes into their flatter test configurations, are also modeled. Results of these structural analyses are then compared to the measured panel structural response. Good correlation is observed between the analysis results and displacement test data throughout deep postbuckling up to global failure, suggesting that nonlinear material behavior is an important component of the actual panel structural response. Author
Nonlinearity; Panels; Stiffness; Structural Analysis; Composite Materials; Mechanical Properties
20060013467 NASA Langley Research Center, Hampton, VA, USA
Thermal Conductivity of Polyimide/Nanofiller Blends
Ghose, S.; Watson, K. A.; Delozier, D. M.; Working, D. c.; Connell, J. W.; Smith, J. G.; Sun, Y. P.; Lin, Y.; [2006]; 15 pp.; In English; SAMPE 2006 Symposium and Exhibition (51st ISSE), 30 Apr. - 4 May 2006, Long Beach, CA, USA; Original contains color and black and white illustrations Contract(s)/Grant(s): 23-612-20-07-12; Copyright; Avail.: CASI: A03, Hardcopy
In efforts to improve the thermal conductivity of Ultem(TM) 1000, it was compounded with three carbon based nano-fillers. Multiwalled carbon nanotubes (MWCNT), vapor grown carbon nanofibers (CNF) and expanded graphite (EG) were investigated. Ribbons were extruded to form samples in which the nano-fillers were aligned. Samples were also fabricated by compression molding in which the nano-fillers were randomly oriented. The thermal properties were evaluated by DSC and TGA, and the mechanical properties of the aligned samples were determined by tensile testing. The degree of dispersion and alignment of the nanoparticles were investigated with high-resolution scanning electron microscopy. The thermal conductivity of the samples was measured in both the direction of alignment as well as perpendicular to that direction using the Nanoflash technique. The results of this study will be presented. Author
Fabrication; Mechanical Properties; Mixtures; Nanoparticles; Polyimides; Thermal Conductivity
Source: NASA
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