Viscoelastic Compaction Effects on Void Transport During Autoclave and Out-Of-Autoclave Thermoset Prepreg Manufacturing of Aerostructures

  • Ahmed Salem

Student thesis: Master's Thesis


In recent years, the out-of-autoclave process has been introduced to various industrial applications, including infrastructure, automotive, transportation, and aerospace; however, the quality of the manufactured composites remains inadequate for the latter applications. The out-of-autoclave process cuts the normal capital and labor cost of the autoclave process. The quality in terms of void levels is yet to be achieved by the current out-of-autoclave manufacturing techniques. In this work, compaction effects on void transport during autoclave and out-of-autoclave manufacturing processing of prepreg materials is analyzed. Prepreg materials allow for better testing conditions, due to uniformity, reduces waste of resin, and a shorter cure time. To investigate compaction effects, the manufacturing processes of a prepreg are mimicked by varying various parameters, and the resulting behavior is evaluated. The uncured glass epoxy prepreg specimens of different layers (4, 8 and 12) are characterized using a creep system under different pressures and temperatures. These specimens were scanned before and after creep testing to study voids and observe microstructure using X-ray computed tomography. The effect of temperature on creep strain and fiber volume fraction were investigated. The experimental results show that temperature and pressure have a significant effect on the compaction behavior, while the effect of the number of layers is negligible. The experiment results show that fiber volume fraction and creep strain increase with increasing temperature from room temperature (25 °C) to 90 °C. On the other hand, It is observed form X-ray computed tomography post-processing analysis that the void volume ratio increase with increasing the number of layers.
Date of AwardMay 2020
Original languageAmerican English


  • Out-of-autoclave Manufacturing
  • Prepregs
  • Creep
  • X-ray Computed Tomography
  • Porosity.

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