Through Thickness Reinforcement of Tubular and Conical Preforms for Hot Structure Applications

C-C material systems have high strength:weight ratios at high temperatures, making them well suited for future hot structure designs.nbsp; However legacy C-C solutions are subject to poor through thickness propertiesnbsp;(for 2D laminates), or manufacturing speed and capacity issuesnbsp;(for Cartesian billets.)nbsp; These issues are often compounded for tubular or conical geometries.nbsp;nbsp;nbsp;With this SBIR Phase I submission TEAM, Inc. proposes to advance the state art for tubular and conical preforming methods for use innbsp;C-Cnbsp;hot structure applications.nbsp; A parallel process development and testing program is proposed:nbsp;nbsp;Process Development:nbsp; We will use ldquo;off the shelfrdquo; and versatile braiding technology to demonstrate fabrication of conical, carbon fiber preform(s) with up to 1rdquo; wall thickness and conical geometry. nbsp;We will modify TEAM#39;snbsp;custom designed, automated z-stitching line to insert stitches into a conical geometry preform at controlled and repeatable spacing(s).nbsp;nbsp;Testing Program:In parallel with the process development, we will quickly fabricate flat panel test coupons of stitched and un-stitched braided laminates. (A phenolic-resin system will be used to meet cost and schedule constraints in Phase I.)nbsp; ~Half the panels will be tested by partner Southern Research Institute to characterize in-plane and inter-laminar tensilenbsp;properties of stitched vs. un-stitched variants.nbsp; The other ~half of panels will be delivered as-is for potential C-C densification and testing by NASA or by TEAM at beginning of Phase II.nbsp;nbsp;The advantage of the proposed approach is that both the braiding process and the stitching work cell are easily scalednbsp;in terms of part size and geometry.nbsp; Through thickness propertynbsp;issues with traditional C-C tape-lay are addressed by the proposed stitching process.nbsp; Cost / capacity / geometric constraint issues associated with Cartesian / Polar billets are addressed by versatility and relative speed of the braiding and z-stitching processes.