NASA Scientific and Technical Aerospace Reports

The National Aeronautics and Space Administration’s (NASA) Marshall Space Flight Center (MSFC) continues research
into the utilization of photonic materials for spacecraft propulsion. Spacecraft propulsion, using photonic materials, will be
achieved using a solar sail. A solar sail operates on the principle that photons, originating from the sun, impart pressure to the
sail and therefore provide a source for spacecraft propulsion. The pressure imparted to a solar sail can be increased, up to a
factor of two if the sun-facing surface is perfectly reflective. Therefore, these solar sails are generally composed of a highly
reflective metallic sun-facing layer, a thin polymeric substrate and occasionally a highly emissive back surface. Near term solar
sail propelled science missions are targeting the Lagrange point 1 (L1) as well as locations sunward of L1 as destinations.
These near term missions include the Solar Polar Imager’ and the L1 Diamond ‘. The Environmental Effects Group at NASA’s
Marshall Space Fliglit Center (MSFC) continues to actively characterize solar sail material in preparation for these near term
solar sail missions. Previous investigations indicated that space environmental effects on sail material thermo-optical
properties were minimal and would not significantly affect the propulsion efficiency of the sail3-’. These investigations also
indicated that the sail material mechanical stability degrades with increasing radiation exposure. This paper will further
quantify the effect of space environmental exposure on the mechanical properties of candidate sail materials. Candidate sail
materials for these missions include Aluminum coated Mylar TM, Teonexm, and CP1 (Colorless Polyimide). These materials
were subjected to uniform radiation doses of electrons and protons in individual exposures sequences. Dose values ranged
from 100 Mrads to over 5 Grads. The engineering performance property responses of thermo-optical and mechanical
properties were characterized. The contribution of Near Ultraviolet (NUV) radiation combined with electron and proton
radiation was also investigated. Conclusions will be presented providing a gauge of measure for engineering performance
stability for sails operating in the L1 space environment.
Author
Solar Sails; Polyimides; Mylar (Trademark); Radiation Effects
20040111504 Delaware Univ., Newark, DE
Yarn Pull-Out as a Mechanism for Dissipation of Ballistic Impact Energy in Kevlar KM-2 Fabric, Part 1: Quasi- Static
Characterization of Yarn Pull-Out
Kirkwood, Keith M.; Kirkwood, John E.; Lee, Young S.; Egres, Ronald G., Jr.; Wetzel, Eric D.; May 2004; 32 pp.; In English;
Original contains color illustrations
Contract(s)/Grant(s): DAAD19-01-2-0001
Report No.(s): AD-A425479; ARL-CR-537; No Copyright; Avail: CASI; A03, Hardcopy
Yarn pull-out can be an important energy absorption mechanism during the ballistic impact of woven Kevlar fabric. This
study reports the effects of fabric length, number of yarns pulled, arrangement of yarns, and transverse tension on the
force-displacement curves for yarn pull-out tests on Kevlar KM-2 fabric under laboratory conditions. A semi-empirical model
is presented for predicting the yarn pull- out force and energy as a function of pull-out distance, including both yarn
uncrimping and subsequent yarn translation. This model is found to replicate the experimental data to a high degree of
accuracy, and should prove useful for understanding ballistic experiments and improving computational modeling of fabrics.
DTIC
Ballistics; Energy Dissipation; Fabrics; Impact; Kevlar (Trademark); Terminal Ballistics; Yarns
20040111506 Army Research Lab., Aberdeen Proving Ground, MD
Hybrid Fiber Sizings for Enhanced Energy Absorption in Glass-Reinforced Composites
Jensen, Robert E.; McKnight, Steven H.; Flanagan, Dave P.; Teets, Alan R.; Harris, Donovan; Jul. 2004; 45 pp.; In English;
Original contains color illustrations
Contract(s)/Grant(s): Proj-AH43
Report No.(s): AD-A425481; ARL-TR-3241; ARL-TR-3241; No Copyright; Avail: CASI; A03, Hardcopy
Achieving high-impact energy absorption without loss of structural performance in a glass fiber-reinforced composite can
be obtained through a materials by design approach of the fiber matrix interphase through modification of current
commercially formulated silane-based fiber-sizing packages. In this report, we document the structural and impact
performance of composites produced using a fiber-sizing package designed to provide strong fiber-matrix bonding at lowimpact
rates and weak fiber-matrix bonding at high-impact rates. Additionally, enhancement of post-failure behavior at
high-impact rates via increased absorption of frictional energy during fiber-matrix pullout was explored through control of the
surface roughness and texture of the glass fibers. A unique inorganic-organic hybrid fiber-sizing formulation was successfully
applied at a commercial E-glass manufacturing facility to produce rovings as well as woven fabric reinforcements. Composite
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