Southwest Research Institute 2001 Annual Report, Engineering Dynamics

Ballistics research and explosive loading of structures are important areas under investigation at the Institute. SwRI engineers and scientists use experimental techniques and large-scale numerical simulations to study the dynamic response of materials and structures to extreme loads and harsh environments. Military and civilian applications include armor studies, ballistics studies of fuel tanks and aircraft engines, and materials evaluations of protective armors and shields.

SwRI researchers are conducting a comprehensive investigation to qualify a replacement material for the foam that fills air voids adjacent to fuel tanks in jet aircraft. The material currently in use contains an ozone-depleting substance and is no longer produced. Institute researchers surveyed a number of candidate foams, selecting the best through screening and acceptance tests. Ballistic qualification testing will simulate operational conditions, using a full-scale wing simulator, live ammunition, and fuel.

Now in the second year of a multiyear effort, Institute researchers continue to test and evaluate active protection concepts for the U.S. Army's future combat systems. Designed to protect vehicles from large-caliber anti-tank weapons, active protection systems integrated with innovative lightweight armor technologies will provide vehicles with required ballistic protection at substantial weight savings over conventional heavy armor approaches. Through funding by the U.S. Army Tank-Automotive Research, Development, and Engineering Center, SwRI researchers are using analytical and computational tools, combined with sophisticated experiments, to define the debris fields produced by the interaction of an active protection system with a ballistic threat.

Though gas turbine aircraft engines are designed to be highly safe, the potential for catastrophic failure still exists. To mitigate and contain the damage of such failures and the collateral damage to adjacent structures and perhaps personnel, engine designers are incorporating barriers into the engine cowling to contain these engine fragments. Institute researchers have been contracted to test and evaluate candidate containment materials, using specialized fragment launchers and state-of-the-art diagnostic instrumentation. The results should allow designers to optimize the weight efficiency and impact resistance of these barriers.

SwRI's program to evaluate and develop methodologies to decrease the effects of terrorist actions continues. Studies include determining the effects of close-in blast and fragmentation on vehicles, structures and buildings, protective personnel shields, and building windows. Vehicular armor systems are also being studied for their ability to defeat small-arms threats.

The Institute recently expanded its small arms testing capabilities by modifying its Tube Range Facility to comply with the National Institute of Justice (NIJ) standard for Ballistic Resistance of Personal Body Armor. SwRI is meeting the requirements of the Voluntary Compliance Testing Program and soon will be scheduled to begin the approval process to become an official NIJ test laboratory. Once approved, the Institute will be one of only three test laboratories in the United States certified to test personal body armor to NIJ standards.

An internal research program is under way to explore the use of explosives and impact to characterize near-Earth objects (NEOs), asteroids whose orbital path around the sun brings them very near to Earth. Impacts of NEOs on the order of 5 kilometers in diameter could produce significant damage to Earth's ecosphere. Any intervention technique (such as changing the orbital path of the NEO or breaking it into pieces that are then dispersed) will require knowledge of the composition and structure of the NEO, including its density, strength, and cohesiveness. SwRI engineers are performing numerical simulations of explosive loading on a NEO to examine how an asteroid's composition and properties can be determined. These loading simulations will be verified by explosive tests in an evacuated test facility at the SwRI ballistics range. The studies will help engineers design charges and instrumentation to be used on future space missions to characterize NEOs.

The Institute has an international reputation in penetration mechanics and penetration modeling. During the past year, the first-principles, predictive analytical models developed by Institute scientists have been extended. It is known that, experimentally, adding resin to ballistic fibers to provide stiffness so that a shape can be formed and maintained, as with a soldier's helmet, decreases the ballistic performance of the fibers. SwRI has developed an analytical model that shows this effect and provides a physical explanation for the observed phenomenology. Another model has been developed that predicts the penetration of kinetic energy segments into armor steel as a function of the full spectrum of impact velocity, aspect ratio of the segment, and impact inclination; the model predictions are 90-95 percent accurate. This analytical model provides a useful design tool to evaluate the effectiveness of advanced armor systems.

Copyright© 2002 by Southwest Research Institute. All rights reserved under U.S. Copyright Law and International Conventions. No part of this publication may be reproduced in any form or by any means, electronic or mechanical, including photocopying, without permission in writing from the publisher. All inquiries should be addressed to Communications Department, Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas 78228-0510, phone (210) 522-2257, fax (210) 522-3547.