Porosity-Free Molded Surfaces for Out-of-Autoclave Composites

Challenges presented with large-scale usable composite structures are quickly being solved with the development of out-of-autoclave (OOA) technology. Structures well over 15 ft (5 m) now bypass the autoclave thanks to material suppliers who have been modifying their prepreg systems to match high performance of structures previously manufactured in the autoclaves. The problem of tool surface imperfections – surface pitting – has not been adequately addressed, however. Surface pitting on flat tooling has been eliminated with the help of PTFE film, but the nonstick ply does not conform well to contoured surfaces, making it unpractical for most aircraft applications. Some other developments have come with significant increases in material and labor costs.

The paper and slides discuss an innovative approach to solve surface pitting issues by creating microstructures on the tool surfaces. A new method is under investigation to create similar structures directly on tool surfaces and thus achieve same porosity-free surface finish as woven release, but without wrinkles, on contoured parts and at a fraction of the cost. To test the microstructure designs, 6 x 6 in. (150 x 150 mm) panels made of 5320-1/T650 fabric were processed and evaluated for surface porosity presence.

© 2013 Aerospace Materials Processing LLC. Reprinted by permission. Presented at: Composites Manufacturing 2014, SME, April 8-10, 2014, Covington, KY.