SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 44, ISSUE 9 - MAY 5, 2006

24 COMPOSITE MATERIALS
Includes physical, chemical, and mechanical properties of laminates and other composite materials.

20060011232 NASA Glenn Research Center, Cleveland, OH, USA

Development of Design Analysis Methods for C/SiC Composite Structures

Sullivan, Roy M.; Mital, Subodh K.; Murthy, Pappu L. N.; Palko, Joseph L.; Cueno, Jacques C.; Koenig, John R.; March 2006; 26 pp.; In English; Original contains color illustrations Report No.(s): NASA/TP-2006-214005; E-15327; Copyright; Avail.: CASI: A03, Hardcopy

The stress-strain behavior at room temperature and at 1100 C (2000 F) was measured for two carbon-fiber-reinforced silicon carbide (C/SiC) composite materials: a two-dimensional plain-weave quasi-isotropic laminate and a three-dimensional angle-interlock woven composite. Micromechanics-based material models were developed for predicting the response properties of these two materials. The micromechanics based material models were calibrated by correlating the predicted material property values with the measured values. Four-point beam bending sub-element specimens were fabricated with these two fiber architectures and four-point bending tests were performed at room temperature and at 1100 C. Displacements and strains were measured at various locations along the beam and recorded as a function of load magnitude. The calibrated material models were used in concert with a nonlinear finite element solution to simulate the structural response of these two materials in the four-point beam bending tests. The structural response predicted by the nonlinear analysis method compares favorably with the measured response for both materials and for both test temperatures. Results show that the material models scale up fairly well from coupon to subcomponent level. Author

Composite Structures; Micromechanics; Stress-Strain Relationships; Carbon Fibers; Woven Composites; Finite Element Method; Fiber Composites; Design Analysis

20060011267 NASA Langley Research Center, Hampton, VA, USA, National Inst. of Aerospace, Hampton, VA, USA

Analysis of Composite Panel-Stiffener Debonding Using a Shell/3D Modeling Technique

Krueger, Ronald; Minguet, Pierre J.; April 2006; 30 pp.; In English; Original contains color and black and white illustrations Contract(s)/Grant(s): NAS1-02117; DAAH10-02-2-0001; WBS 23-063-30-22 Report No.(s): NASA/CR-2006-214299; NIA-Rept-2006-02; Copyright; Avail.: CASI: A03, Hardcopy

Interlaminar fracture mechanics has proven useful for characterizing the onset of delaminations in composites and has been used with limited success primarily to investigate onset in fracture toughness specimens and laboratory size coupon type specimens. Future acceptance of the methodology by industry and certification authorities however, requires the successful demonstration of the methodology on structural level. For this purpose a panel was selected that was reinforced with stringers. Shear loading cases the panel to buckle and the resulting out-of-plane deformations initiate skin/stringer separation at the location of an embedded defect. For finite element analysis, the panel and surrounding load fixture were modeled with shell element. A small section of the stringer foot and the panel in the vicinity of the embedded defect were modeled with a local 3D solid model. A failure index was calculated by correlating computed mixed-mode failure criterion of the graphite/epoxy material. Author

Finite Element Method; Debonding (Materials); Composite Structures; Fracture Mechanics; Fracture Strength; Graphite- Epoxy Composites; Delaminating

20060011316 Wisconsin Univ., Madison, WI, USA

Nanostructured Shape Memory Alloys. Final Technical Report

Bakke, P.; Crone, W.; Drugan, W.; Ellis, A.; Perepezko, J.; January 2006; 14 pp.; In English Report No.(s): DE2006-841686; No Copyright; Avail.: Department of Energy Information Bridge

With this grant we explored the properties that result from combining the effects of nanostructuring and shape memory using both experimental and theoretical approaches. We developed new methods to make nanostructured NiTi by melt-spinning and cold rolling fabrication strategies, which elicited significantly different behavior. A template synthesis method was also used to created nanoparticles. In order to characterize the particles we created, we developed a new magnetically-assisted particle manipulation technique to manipulate and position nanoscale samples for testing. Beyond characterization, this technique has broader implications for assembly of nanoscale devices and we demonstrated promising applications for optical switching through magnetically-controlled scattering and polarization capabilities. Nanoparticles of nickeltitanium (NiTi) shape memory alloy were also produced using thin film deposition technology and nanosphere lithography. Our work revealed the first direct evidence that the thermally-induced martensitic transformation of these films allows for partial indent recovery on the nanoscale. In addition to thoroughly characterizing and modeling the nanoindention behavior in NiTi thin films, we demonstrated the feasibility of using nanoindention on an SMA film for write-read-erase schemes for data storage. This research has resulted in six journal publications, seven conference proceedings, two masters degrees, and two Ph.D. degrees. NTIS

Nanostructures (Devices); Shape Memory Alloys

Source: NASA