Long Nanofiber Reinforcement of Bulk Ceramics for Extreme Toughness, Strength, and Multifunctionalit
Abstract
AbstractEmerging Navy & DoD applications including hypersonics require development of lightweight ceramic compositeswith enhanced th,ermal stability and shock resistance, necessitating ceramics with high strength and fracturetoughness at elevated temperature. Bulk,ceramics with enhanced fracture toughness and ductile failure behaviorhave been recently engineered via nanoporosity and nanofibers,, albeit with limitations in processing and scale,particularly both length and packing (vol%) of nanofibers. Here, we propose a new p,latform for creating tough andstrong long nanofiber reinforced bulk ceramics at extreme volume fractions and nanofiber lengths far b,eyond whatis currently possible, by combining new findings from across three investigations: (i) synthesis of bulk-scale arraysof al,igned boron nitride nanotubes (A-BNNTs, new, unpublished), (ii) a new bulk nanocomposite laminating (BNL)process developed at MIT, a,nd (iii) model-guided synthesis of high-temperature carbon-matrix nanocompositesreinforced with aligned carbon nanotubes (A-CNTs). T,he new high-quality crystalline and transparent A-BNNTs arean ideal high-temperature reinforcing nanofiber due to their scale, stren,gth, and high thermal stability. The BNLprocess achieves films and laminates of high packing (over 30 vol%) aligned nanofibers with,0 vol% matrix porosityvia a facile mechanical orienting and densifying process of vertically-aligned nanofibers (CNTs and BNNTs) aft,erinfusion with polymer resin at the cm-scale, but to date has only been used with A-CNTs and polymer matrices. Wepropose a BNL for,ceramic-matrix composites (BNL4CMC) process to include A-BNNTs, and we completed deriskingexperiments that show we can use the BNL p,rocess for the phenolic-derived pyrolytic carbon (PyC) matrix,using both A-CNTs and A-BNNTs. Process-structure-property relations wi,ll be established for these new bulkceramic matrix composites (CMCs), with specific aims in BNL4CMC process expansion and scaling, n,anofibermatrixinterfacial characterizations, and physical property assessments. The new BNL4CMC process can be seen asa platform tec,hnology for developing next generations of tough and strong nanofiber-reinforced lightweight CMCswith high packing fractions (~2 tri,llion aligned nanofibers per cm2 of composite) which allows a variety of ceramicmatrices to be targeted for Navy applications includ,ing transparent and opaque armor and high-temperaturelightweighting. Sub-processes of the BNL4CMC process may also realize metal mat,rix composites with the samehigh packing fraction of carbon or other ceramic nanofibers towards fatigue resistant structural metal c,oncepts.Approved for public release.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 05, 2022
- Source ID
- N000142212203
Entities
People
- Brian Wardle
Organizations
- Massachusetts Institute of Technology
- Office of Naval Research
- United States Navy