Out-of-autoclave (OoA) prepreg materials and methods have gained acceptance over the past decade because of the ability to produce autoclave-quality components under vacuum-bag-only (VBO) cure. To achieve low porosity and tight dimensional tolerances, VBO prepregs rely on specific microstructural features and processing techniques. Furthermore, successful cure is contingent upon appropriate material property and process parameter selection. In this article, we review the existing literature on VBO prepreg processing to summarize and synthesize knowledge on these issues. First, the context, development, and defining properties of VBO prepregs are presented. The key processing phenomena and the influence on quality are subsequently described. Finally, cost and environmental performance are considered. Throughout, we highlight key considerations for VBO prepreg processing and identify areas where further study is required.

A review of out-of-autoclave prepregs – Material properties, process phenomena, and manufacturing considerations

pdf/reduction-of-slamming-damage-in-the-hull-of-high-speed-2x5daj8g1f.pdf

Reduction of slamming damage in the hull of high-speed crafts manufactured from composite materials using viscoelastic layers

The Effect of Slamming Impact on Out-of-Autoclave Cured Prepregs of GFRP Composite Panels for Hulls☆

*This paper is declared a work of the U.S. Government and is not subject to copyright protection in the United States.The emergence of bismaleimide composites has fulfilled some of the increasing demand for higher temperature performance aeronautics and space exploration vehicles. This study examines and evaluates three bismaleimide matrix resins and two bismaleimide adhesives and reports on the processing properties of these resins and composites by out-of-autoclave–vacuum-bag-only oven processing. Measurements were conducted under various cure cycles to characterize and correlate thermal and viscoelastic properties of the materials. Specimens of all three aged matrix resins exhibited an out-time life up to 30 days when stored at room temperature. Solid and sandwich panels were fabricated with the out-of-autoclave–vacuum-bag-only process. Because of tooling limitations in industry practices, composite fabrication of these bismaleimides was restricted to a maximum 177℃ curing, followed by a free-standing ...

https://journals.sagepub.com/doi/pdf/10.1177/0731684413503050

Out-of-autoclave processing and properties of bismaleimide composites :

Two manufacturing demonstration panels (1/16th-arc-segments of 10 m diameter cylinder) were fabricated under the composites part of the Lightweight Space Structures and Materials program. Both panels were of sandwich construction with aluminum core and 8-ply quasi-isotropic graphite/epoxy facesheets. One of the panels was constructed with in-autoclave curable unidirectional prepreg (IM7/977-3) and the second with out-of-autoclave unidirectional prepreg (T40-800B/5320-1). Following NDE inspection, each panel was divided into a number of small specimens for material property characterization and a large (0.914 m wide by 1.524 m long) panel for a buckling study. Results from the small specimen tests were used to (a) assess the fabrication quality of each 1/16th arc segment panel and (b) to develop and/or verify basic material property inputs to Finite Element analysis models. The mechanical performance of the two material systems is assessed at the coupon level by comparing average measured properties such as flatwise tension, edgewise compression, and facesheet tension. The buckling response of the 0.914 m wide by 1.524 m long panel provided a comparison between the in- and out-of autoclave systems at a larger scale.

/pdf/mechanical-characterization-of-in-and-out-of-autoclave-cured-1crv0ltsw9.pdf

Mechanical Characterization of In and Out-of-Autoclave Cured Composite Panels for Large Launch Vehicles

The National Aeronautics and Space Administration (NASA) Exploration Systems Mission Directorate initiated an Advanced Composite Technology Project through the Exploration Technology Development Program in order to support the polymer composite needs for future heavy lift launch architectures. As an example, the large composite dry structural applications on Ares V inspired the evaluation of autoclave and out-of-autoclave (OOA) composite materials. A NASA and industry team selected the most appropriate materials based on component requirements for a heavy lift launch vehicle. Autoclaved and OOA composites were fabricated and results will highlight differences in processing conditions, laminate quality, as well as initial room temperature thermal and mechanical performance. Results from this study compare solid laminates that were both fiber-placed and hand-laid. Due to the large size of heavy-lift launch vehicle composite structures, there is significant potential that the uncured composite material or prepreg will experience significant out-life during component fabrication. Therefore, prepreg out-life was a critical factor examined in this comparison. In order to rigorously test material suppliers recommended out-life, the NASA/Industry team extended the out-time of the uncured composite prepreg to values that were approximately 50% beyond the manufacturers out-time limits. Early results indicate that the OOA prepreg composite materials suffered in both composite quality and mechanical property performance from their extended out-time. However, the OOA materials performed similarly to the autoclaved composites when processed within a few days of exposure to ambient "shop" floor handling. Follow on studies evaluating autoclave and OOA aluminum honeycomb core sandwich composites are planned.

/pdf/comparison-of-autoclave-and-out-of-autoclave-composites-34xv7sl3mb.pdf

Comparison of Autoclave and Out-of-Autoclave Composites

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Comparison of Autoclave and Out-of-Autoclave Composites