Naval Surface Warfare Center

About: Naval Surface Warfare Center is a facility organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Sonar & Radar. The organization has 2855 authors who have published 3697 publications receiving 83518 citations. The organization is also known as: NSWC.

High-frequency/low-frequency synthetic aperture sonar

Abstract: The HF/LF SAS is a high resolution SAS developed by COASTSYSTA and Northrop Grumman for the shallow water (SW) and very shallow water (VSW) regimes This sonar suite has recently been delivered to COASTSYSTA and it is currently undergoing field testing This article describes this sonar and the type of resolution and acoustical images which are expected from this sonar The application of this sonar to the SW and VSW regimes required the development of a novel method of motion compensation A description of this method and the type of accuracy's expected from this technique are presented Finally, a look at future broad band system and their predicted performance is presented© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering Downloading of the abstract is permitted for personal use only

Ballistic Impact Resistance of SMA and Spectra Hybrid Graphite Composites

Abstract: The effect of adding small amounts of high strain hybrid components on the impact resistance of graphite epoxy composites subjected to projectiles traveling at ballistic velocities (greater than 900 ft/sec) has been studied. The hybrid components tested include superelastic shape memory alloy (SMA) and a high performance extended chain polyethylene (ECPE) known as Spectram. In all cases, the embedded SMA fibers were pulled through the graphite without straining to their full potential. It is believed that this is due to high strain rate effects coupled with a strain mismatch between the tough SMA and the brittle epoxy resin. However, a significant increase in energy absorption was found by adding ECPE and ECPE/SMA layers to the backface of the composite.

Polyurethane networks with controlled architecture of dangling chains

Abstract: Network formation from A x + B y precursors (A + B → A - B) with functionality and molecular weight distributions is described by the statistical theory of branching processes. Network formation is described in terms of sol and gel fractions, dangling chains, elastically active network chains (EANC), elastically active crosslinks, free chain ends and branch points partitioned between sol and gel. Various definitions of an EANC are considered. The general relations are applied to a special case of A1 + A2 + A3/B2 system. It is show how the size and weight fractions of dangling chains can be varied indepently by varying the functionality or molecular weight distributions. This is demonstrated experimentally analyzing corresponding polyetherurethane networks prepared from mixtures of polyoxypropylene polyols. The width of the main transition region correlates with the fraction of material in dangling chains. The dependence of the equilibrium shear modulus on the concentration of EANC's indicates much weaker intermolecular interactions for networks with many short dangling chains compared with systems having few longer dangling chains.

Silicone Polymer Composites for Thermal Protection System: Fiber Reinforcements and Microstructures

Abstract: A new class of silicone polymer matrix composites was evaluated using a simulated solid rocket motor test apparatus. Conversion of this organic silicone polymer to a ceramic (i.e. silica) structure on exposure to flame impingement or high temperature, accounts for its outstanding thermal stability. A research program was aimed to develop and evaluate this new class of thermal protection materials for military applications. This article presents the effects of the type and form of reinforcements on the thermal performance of a novel class of silicone polymer matrix composites. Reinforcement types such as glass, silica, quartz, NextelTM, and NicalonTM were used. Reinforcement forms such as random continuous-fiber mat, chopped-fiber mat, 2-D fabric, 3-D fabric, chopped roving, and broadgood tapes with different ply angles were tested. Detailed microstructural, mass loss, and peak erosion analyses were conducted on the phenolic-based matrix composite (control) and silicone-based matrix composites to understan...