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Fracture in Phenolic Impregnated Carbon AblatorThe thermal protection materials used for spacecraft heat shields are subjected to various thermal-mechanical loads during an atmospheric entry which can threaten the structural integrity of the system. This paper discusses the development of a novel technique to understand the failure mechanisms inside thermal protection materials. The focus of research is Phenolic Impregnated Carbon Ablator (PICA). It has successfully flown on the Stardust spacecraft and is the TPS material chosen for the Mars Science Laboratory (MSL) and Dragon spacecraft. Although PICA has good thermal properties, structurally, it is a weak material. In order to thoroughly understand failure in PICA, fracture tests were performed on FiberForm* (precursor of PICA), virgin and charred PICA materials. Several samples of these materials were tested to investigate failure mechanisms at a microstructural scale. Stress-strain data were obtained simultaneously to estimate the fracture toughness. It was found that cracks initiated and grew in the FiberForm when a critical stress limit was reached such that the carbon fibers separated from the binder. However, both for virgin and charred PICA, crack initiation and growth occurred in the matrix (phenolic) phase. Both virgin and charred PICA showed greater strength values compared to FiberForm coupons, confirming that the presence of the porous matrix helps in absorbing the fracture energy.
Document ID
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Agrawal, Parul
(Engineering Research and Consulting, Inc. Moffett Field, CA, United States)
Chavez-Garcia, Jose F.
(Engineering Research and Consulting, Inc. Moffett Field, CA, United States)
Date Acquired
August 25, 2013
Publication Date
June 27, 2011
Subject Category
Nonmetallic Materials
Report/Patent Number
Meeting Information
Meeting: 42nd AIAA Thermophysics Conference
Location: Honolulu, HI
Country: United States
Start Date: June 27, 2011
End Date: June 30, 2011
Sponsors: American Inst. of Aeronautics and Astronautics
Funding Number(s)
Distribution Limits
Public Use Permitted.
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