SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 44, ISSUE 14 - JULY 18, 2006

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

20060019463 Alabama Univ., Birmingham, AL USA

Development of Computational Models and Input Sensitivity Study of Polymer Reinforced Concrete Masonry Walls Subjected to Blast

Davidson, James S; Sudame, Sushant; Dinan, Robert J; Dec 2004; 170 pp.; In English; Original contains color illustrations Contract(s)/Grant(s): F08637-02-C-7027; Proj-4918 Report No.(s): AD-A446367; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446367; Avail.: CASI: A08, Hardcopy

Computational models were developed and used to simulate polymer reinforced masonry walls subjected to blast loading and the models were used to understand the response of the structure. LS-DYNA, a nonlinear finite element solver, was used. Model development challenges were considered, and appropriate input parameters were determined. With these pedestal values, a baseline model of one unit width of concrete masonry block was developed, and the response under two load conditions was studied. Dimensional and mechanical variants involved in the system were varied to study their effect on wall behavior. The effects of door and window openings on the performance of the polymer reinforcement were evaluated. This report also presents an analysis of strain rate that occurs in the polymer coating and results were compared to theory-based closed form solutions. Finally, the static nonlinear capabilities of LS-DYNA were used to describe the static resistance of the system, and a theoretical description of a simply supported membrane subjected to pressure load is provided and compared with nonlinear finite element results. DTIC

Blast Loads; Composite Materials; Concretes; Masonry; Mathematical Models; Models; Sensitivity; Structural Analysis; Walls

20060020264 NASA Glenn Research Center, Cleveland, OH, USA

Material Issues in Space Shuttle Composite Overwrapped Pressure Vessels

Sutter, James K.; Jensen, Brian J.; Gates, Thomas S.; Morgan, Roger J.; Thesken, John C.; Phoenix, S. Leigh; [2006]; 13 pp.; In English; 9th Conference on Aging Aircraft, 6-9 Mar. 2006, Atlanta, GA, USA; Original contains color and black and white illustrations Contract(s)/Grant(s): 515-02-01-03-03-01-07; No Copyright; Avail.: CASI: A03, Hardcopy

Composite Overwrapped Pressure Vessels (COPV) store gases used in four subsystems for NASA's Space Shuttle Fleet. While there are 24 COPV on each Orbiter ranging in size from 19-40', stress rupture failure of a pressurized Orbiter COPV on the ground or in flight is a catastrophic hazard and would likely lead to significant damage/loss of vehicle and/or life and is categorized as a Crit 1 failure. These vessels were manufactured during the late 1970's and into the early 1980's using Titanium liners, Kevlar 49 fiber, epoxy matrix resin, and polyurethane coating. The COPVs are pressurized periodically to 3-5ksi and therefore experience significant strain in the composite overwrap. Similar composite vessels were developed in a variety of DOE Programs (primarily at Lawrence Livermore National Laboratories or LLNL), as well as for NASA Space Shuttle Fleet Leader COPV program.

The NASA Engineering Safety Center (NESC) formed an Independent Technical Assessment (ITA) team whose primary focus was to investigate whether or not enough composite life remained in the Shuttle COPV in order to provide a strategic rationale for continued COPV use aboard the Space Shuttle Fleet with the existing 25-year-old vessels. Several material science issues were examined and will be discussed in this presentation including morphological changes to Kevlar 49 fiber under stress, manufacturing changes in Kevlar 49 and their effect on morphology and tensile strength, epoxy resin strain, composite creep, degradation of polyurethane coatings, and Titanium yield characteristics. Derived from text

Pressure Vessels; Composite Wrapping; Space Shuttles; Kevlar (Trademark); Fiber Composites; Epoxy Matrix Composites; Polyurethane Resins; Resin Matrix Composites; Damage

20060020911 Rockwell Scientific Co., LLC, Thousand Oaks, CA USA

Materials Design Principles for the Dynamic Fracture of Larminar Composite Structures

Cox, Brian N; Feb 28, 2006; 84 pp.; In English; Original contains color illustrations Contract(s)/Grant(s): W911NF-05-C-0073 Report No.(s): AD-A447105; PR71267-01; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA447105; Avail.: CASI: A05, Hardcopy

The goal of this program of basic research is to develop engineering principles for dealing with dynamic, multiple cracking damage in laminated structures, including large scale crack bridging, due to through-thickness reinforcement, and friction. Bridging and friction are treated by materials models at the smallest scales relevant to the mechanisms. By reference to the fundamentals of the dynamic growth of single cracks, which is already largely understood, simple approaches are being formulated to calculate the development of distributed delamination cracks in laminated structures with non-trivial geometry and general loading conditions. To treat large scale bridging effects, structural sub-component models must support dimensions of tilde100 mm or more. The approach bridges scales ranging from this characteristic structural size down to that of micromechanisms (friction, fiber bridging) within the process zone of a single crack. By doing this, a direct link is being established between structural performance and materials design. DTIC

Composite Materials; Composite Structures; Design Analysis; Fracturing; Laminates

20060020963 Virginia Polytechnic Inst. and State Univ., Blacksburg, VA USA

Structural Piezoelectric Single Crystal Array Networks (Structural P-SCAN)

Kampe, S L; Mar 2006; 7 pp.; In English Contract(s)/Grant(s): DAAD19-01-1-0714 Report No.(s): AD-A447243; No Copyright; Avail.: CASI: A02, Hardcopy

Experimental verification of enhanced passive mechanical damping as derived from ferroelectric-embedded particulates within a metal matrix composite has been demonstrated. Specifically, experimental results indicate relatively high damping is exhibited by composites containing a discontinuous dispersion of ferroelectric (tetragonal) BaTiO(sub 3) particulate; damping capability is reduced as temperature increases and a transformation to a cubic form occurs. Experiments performed at the Los Alamos Neutron Science Center (LANSCe) indicate that the mechanism of damping is associated with ferroelectric domain rotation that occurs in response to external stress. Early results additionally indicated that the stability of tetragonal form of BaTiO(sub 3) is very sensitive to a variety of processing-related factors serve to limit the processing options available to synthesize the composite.

Processing studies that examined the influence of ferroelectric particle size, interfacial strength, and composite processing methodology were performed. Overall, results indicate a potential for effective multifunctional (strengthening plus damping) behavior by ferroelectric reinforcement strategies provided that the tetragonal form of the particulate can be maintained through processing. Further, the mechanisms of enhanced damping and strengthening should be directly extendable to reinforcement by shape memory alloys (SMA), since both involve energy absorption by the activation of certain crystallographic translations. DTIC

Damping; Metal Matrix Composites; Piezoelectric Crystals; Single Crystals

20060020964 State Univ. of New York, Stony Brook, NY USA

Robust Multivariate Evaluation and Failure Prediction of Inhomogeneous Solids Based on Inverse Analysis

Nakamura, Toshio; Dec 31, 2005; 13 pp.; In English; Original contains color illustrations Contract(s)/Grant(s): DAAD19-02-1-0333 Report No.(s): AD-A447244; No Copyright; Avail.: CASI: A03, Hardcopy

During last three years, successful developments and implementations of inverse analyses techniques for advanced materials have been carried out. Furthermore, novel computational approaches were developed to ascertain failure characteristics of inhomogeneous structural systems. These outcomes are described in the published and submitted journal papers. For the identification and evaluations, experimental procedures were developed for nano-, micro-indentations of elastic-plastic graded materials and anisotropic materials. For composites, two separate techniques were developed to identify the embedded delamination and surface damage. Furthermore, hygro-thermal properties of fiber-reinforced materials were determined with an inverse analysis technique. Most of these procedures were conducted with real experiments using instrumented indenters, accelerated weather chambers, loading machines, etc. In terms of developing a new computational toolto understand the mechanics of complex material/structural systems, dynamic crack propagation in functionally graded materials was simulated. Subsequently the method was extended to simulate so-call foreign object damage (FOD). FOD is a main concern in aerospace and power generation industries. In this analysis, an impact of single particle onto heterogeneous material was considered. In addition, 3D modeling of fibrous materials has been initiated to study the deformation and failure of fibrous materials. DTIC

Crack Propagation; Delaminating; Failure Analysis; Multivariate Statistical Analysis; Predictions; Solids

20060021027 Massachusetts Inst. of Tech., Cambridge, MA USA

Ultrasonic Wave Propagation in Thick, Layered Composites Containing Degraded Interfaces

Small, Peter D; Jun 2005; 94 pp.; In English Report No.(s): AD-A447401; No Copyright; Avail.: CASI: A05, Hardcopy

The ultrasonic wave propagation of thick, layered composites containing degraded bonds is investigated. A theoretical one-dimensional model of three attenuative viscoelastic layers containing two imperfect interfaces is introduced. Elastic material properties and measured values of ultrasonic phase velocity and attenuation are used to represent E-glass and vinyl ester resin fiber-reinforced plastic (FRP) laminate, syntactic foam, and resin putty materials in the model. The ultrasonic phase velocity in all three materials is shown to be essentially constant in the range of 1.0 to 5.0 megahertz (MHz). The attenuation in all three materials is constant or slightly increasing in the range 1.0 to 3.0 MHz. Numerical simulation of the model via the mass-spring-dashpot lattice model reveals the importance of the input signal shape, wave speed, and layer thickness on obtaining non-overlapping, distinct return signals in pulse-echo ultrasonic nondestructive evaluation. The effect of the interface contact quality on the reflection and transmission coefficients of degraded interfaces is observed in both the simulated and theoretical results. DTIC

Composite Materials; Elastic Properties; Ultrasonic Radiation; Ultrasonics; Wave Propagation

Source: NASA