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Study of Permeability Testing Methods for Composite Laminates

Authors
  • Busse, Thomas S.
  • Yu, Giannina Marie M.
Publication Date
Jun 01, 2020
Source
[email protected]
Keywords
License
Unknown
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Abstract

Permeability measurements are strong indicators of the effectiveness of evacuation channels within a composite prepreg. The effectiveness of these evacuation channels directly relates to the void content within a processed composite laminate. The goal of Toray Advanced Composites was to compare two permeability tests and determine which one was more reliable, accurate, and economical. The first permeability test method was the Cirrus method, designed by Cirrus Aircraft, a customer of Toray Advanced Composites. The second test was ASTM D8132, the standard method for permeability testing. Additionally, Toray sought to investigate the effect out-time had on the permeability of three different prepreg products using the more feasible permeability test option. For the comparison stage of the project, both the ASTM and Cirrus tests were run 5 times. Different modifications and techniques were recorded during these tests for future consideration on how to improve test efficiency. The Cirrus data yielded an average permeability value of 3.98 x 10-14 m2; while the ASTM test yielded an average permeability value of 7.4 x 10-12 m2. Both tests yielded repeatable data. The Cirrus data yielded a standard deviation of 1.5 x 10-14 m2, and the ASTM data had a standard deviation of 1.8 x 10-12 m2. The order of magnitude difference between the two data sets was determined to be the result of differing sample preparation methods for each test. Qualitative analysis was also used to determine which test was more feasible based on ease of setup, total run time, cost, and amount of material used per test. The ASTM test, on average, took two hours less to prepare and conduct the test compared to the Cirrus test and used 45 in2 less of material per sample. It also cost around $3550 less to prepare and run the test. Due to the minimal resources required to run the ASTM test and its certification as a standard test method, the ASTM test was determined to be the more efficient and more feasible option. The modifications and techniques to run each test more efficiently were written into standard operating procedures for future use and development by Toray engineers and technicians. However, due to the COVID-19 outbreak the out-time experiments were cancelled, and all further work was ended.

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