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High Temperature VARTM of Phenylethynyl Terminated ImidesDepending on the part type and quantity, fabrication of composite structures using vacuum assisted resin transfer molding (VARTM) can be more affordable than conventional autoclave techniques. Recent efforts have focused on adapting VARTM for the fabrication of high temperature composites. Due to their low melt viscosity and long melt stability, certain phenylethynyl terminated imides (PETI) can be processed into composites using high temperature VARTM (HT-VARTM). However, one of the disadvantages of the current HT-VARTM resin systems has been the high porosity of the resultant composites. For aerospace applications, the desired void fraction of less than 2% has not yet been achieved. In the current study, two PETI resins, LaRC PETI-330 and LaRC PETI-8 have been used to make test specimens using HT-VARTM. The resins were infused into ten layers of IM7-6K carbon fiber 5-harness satin fabric at 260 C or 280 C and cured at temperature up to 371 C. Initial runs yielded composites with high void content, typically greater than 7% by weight. A thermogravimetric-mass spectroscopic study was conducted to determine the source of volatiles leading to high porosity. It was determined that under the thermal cycle used for laminate fabrication, the phenylethynyl endcap was undergoing degradation leading to volatile evolution. This finding was unexpected as high quality composite laminates have been fabricated under higher pressures using these resin systems. The amount of weight loss experienced during the thermal cycle was only about 1% by weight, but this leads to a significant amount of volatiles in a closed system. By modifying the thermal cycle used in laminate fabrication, the void content was significantly reduced (typically ~ 3% or less). The results of this work are presented herein.
Document ID
20090039498
Acquisition Source
Langley Research Center
Document Type
Preprint (Draft being sent to journal)
External Source(s)
doi:10.1177/0954008309339935
Authors
Ghose, Sayata (National Inst. of Aerospace Hampton, VA, United States)
Cano, Roberto J. (NASA Langley Research Center Hampton, VA, United States)
Watson, Kent A. (National Inst. of Aerospace Hampton, VA, United States)
Britton, Sean M. (NASA Langley Research Center Hampton, VA, United States)
Jensen, Brian J. (NASA Langley Research Center Hampton, VA, United States)
Connell, John W. (NASA Langley Research Center Hampton, VA, United States)
Herring, Helen M. (Lockheed Martin Engineering and Sciences Co. Hampton, VA, United States)
Linberry, Quentin J. (Western Kentucky University Bowling Green, Kentucky)
Date Acquired
August 24, 2013
Publication Date
April 17, 2009
Publication Information
Publication: High Performance Polymers
Volume: 21
Issue: 5
Subject Category
Composite Materials
Report/Patent Number
LF99-8635
Funding Number(s)
WBS: WBS 984754.02.07.07.15.03
Distribution Limits
Public
Copyright
Public Use Permitted.

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