*********************************
There is now a CONTENT FREEZE for Mercury while we switch to a new platform. It began on Friday, March 10 at 6pm and will end on Wednesday, March 15 at noon. No new content can be created during this time, but all material in the system as of the beginning of the freeze will be migrated to the new platform, including users and groups. Functionally the new site is identical to the old one. webteam@gatech.edu
*********************************
Event Date: Friday, January 27, 2017
Event Time: 11 am
Location: Montgomery Knight 325
Doctoral Thesis Proposal:
Liquid Composite Molding of Conformal Ablative Thermal Protection System Materials
by
Adam T. Sidor
Abstract: Ablative heat shields, or thermal protection systems (TPS), have been used extensively for protecting spacecraft from the the intense aeroheating of atmospheric entry. From ballistic missiles to interplanetary probes to manned vehicles, ablative materials have been employed for the vast majority of entries to date. These materials present significant engineering and processing challenges due to high part counts and/or complex, costly manufacturing and installation. Conformal ablators alleviate these difficulties by utilizing a flexible, rather than rigid, fibrous substrate impregnated with polymer resin. This construction yields high strain to failure allowing large tile sizes, reduced part counts and direct installation onto an aeroshell.
Conformal ablators, much like other fiber-reinforced composites, are fabricated as near net shape parts in a mold. However, state of the art manufacturing mirrors open processes developed for rigid substrate ablators (e.g., PICA, SIRCA) rather than efficient, closed liquid composite molding (LCM) processes. In LCM, resin is injected directly into a fibrous substrate sealed within a matched mold. LCM has existed in some form for decades and has found widespread application in composites manufacturing. To date, though, its application to TPS manufacturing has been limited.
The proposed thesis advances the state of the art by developing a vacuum infusion process (VIP), a subset of LCM, for low density conformal ablators. The process can reduce waste, cost and labor over the state of the art technique. First, a proof of concept demonstrates VIP on conformal phenolic impregnated carbon ablator (C-PICA). The equivalency of the VIP-produced material and the standard is established through material testing. Then, a methodology is proposed to design a conformal ablative heat shield for VIP manufacturing. The methodology leverages the deterministic nature of resin flow to model the VIP process and inform mold design. Pairing the VIP simulation with an approach to tiling facilitates end-to-end design of a conformal ablative heat shield – from geometry to segmented tile layout to manufacturing process. Implementation of the methodology in a software code automates design improving on current manual approaches.
Committee:
Dr. Robert D. Braun (advisor)
Dr. Graeme J. Kennedy (co-advisor)
Dr. Julian J. Rimoli
Ms. Robin A.S. Beck
Dr. Margaret M. Stackpoole
