SYMPOSIA PAPER Published: 01 January 1972

Mechanical Behavior of Three-Dimensional Composite Ablative Materials


The mechanical behavior of a variety of three-dimensional reinforced ablative materials is investigated. The mechanical properties of these materials, which form the outermost surface of reentry vehicles and, therefore, are subjected to external loads, must be known to design the structure. Materials studied included three carbon/phenolics, a quartz/ phenolic, and a quartz/carbon material. Four different weave or reinforcement concepts were used in making these various materials: Narmcowrap, Intremold III, Omniweave, and PFR 3007. Mechanical properties were determined from tension, compression, and flexure tests. All of the tests were conducted at room temperature, and in the tension and compression tests strain gages were installed to obtain the modulus and Poisson's ratio. Results from each of the five systems are presented. Intremold III carbon/phenolic has properties that can be predicted from the properties of its constituent materials. The specimens as manufactured were not symmetrical and, hence, were not uniformly loaded, resulting in predictably lower average failure stresses. Narmcowrap carbon/phenolic was also an asymmetrical material, but the reinforcement prohibited the calculation of an expected load from constituent material properties. Attempts to separate the material into two symmetrical parts were not successful. Results from two types of Omniweave materials are also presented. These materials exhibited some nonlinear stress-strain behavior due to the weaving pattern. The final material, PFR 3007, exhibited a Poisson's ratio close to 1.0 in one direction and 0 in the orthogonal direction. Comparisons of the various materials are made with respect to mechanical behavior. An evaluation of the testing methods and procedures for this class of materials is also given.

Author Information

Adsit, NR
Convair Aerospace Division of General Dynamics, San Diego, Calif.
Carnahan, KR
Convair Aerospace Division of General Dynamics, San Diego, Calif.
Green, JE
U.S. Air Force, Air Force Weapons Laboratory, Albuquerque, N. M.
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Developed by Committee: D30
Pages: 107–120
DOI: 10.1520/STP27743S
ISBN-EB: 978-0-8031-4606-8
ISBN-13: 978-0-8031-0134-0