Extreme Mechanics of Mixed-Dimensional Carbon Nanostructures with Thermally Robust Interfacial Bonds
Abstract
Publicly Releasable Project Abstract: Extreme Mechanics of Bio-inspired Mixed-Dimensional Carbon Nanostructures with Thermally Robust Interfacial Bonds PIs: Mohammad Naraghi (TEES), Chenglin Wu (MUST), Keith A. Nelson (MIT) Materials that exhibit superior energy dissipation in response to impact loading are highly desired for armors and protective clothing. A class of promising candidates for such applications is hybrid 1D-2D nanomaterials where 1D materials (i.e., rebars such as nanowires) are used as reinforcements of 2D materials, e.g., graphene. While defect-free graphene on its own can largely outperforms steel in terms of impact energy dissipation, in practice, defects such as microcracks, can trigger brittle failure in 2D materials, and 1D nanomaterials are used to reinforce against defects. However, it is not clear yet how the energy dissipation in such hybrid nanomaterial depends on rebar arrangement and 1D-2D material interface. This uncertainty hampers meaningful progress in the field. Striving to address this knowledge gap, the goal of this research is to unravel the dependence of crack patterns (crack initiation, growth, deflection and arrest) and impact energy dissipation on 1D-2D material interface strength and orientation/spacing of the rebars. The subject of the work will be a novel 3D nanostructure of carbon Ðcarbon nanofibers (CNF) and graphene (G) Ð with thermally stable interfacial bonds. The CNFs will be fabricated via in situ pyrolysis after controllable placement of their precursors on graphene. The structure will benefit from templated graphitization along CNF-G interface to form strong bonds between them, without disrupting the pristine structure of graphene in contrast to covalent bonding. In terms of mechanical robustness, the structure is reminiscent of tree leaves, in which CNFs (equivalent to the venation system) can effectively deflect/arrest cracks in the graphene (equivalent to the epiderm). The failure initiation and damage due to mechanical loads will be studied in two different length and time scales in an increasing order of system complexity: scale of individual CNF-G interfaces (nanoscale, quasi-static Ð Obj 1) and the scale of CNF-G ensemble (microscale, quasi-static and dynamic Ð Obj 2-3). In Obj 1, we will study junction strength between 1D and 2D materials, as formed by templated graphitization, via innovative nanoscale fragmentation tests. The tests will be designed to promote interface failure prior to CNF or graphene failure. In Obj 2, we will evaluate the interaction between growing cracks and rebars (e.g., crack pinning and crack path deflection) as a function of CNF-G interface strength and arrangement of CNFs via microscale fracture experiments. The experimental design will take input from Obj 1, and the results will be used to modify/validate and verify a phase-field continuum model with anisotropic graphene properties and elastoplastic interfacial behavior at CNF-G interface. The verified continuum models will be used to predict the emerging crack patterns in a hybrid structure subjected to dynamic loading. The model will incorporate strain-rate sensitive load transfers between 1D and 2D material (Maxwell type traction separation relation). The strain rate sensitivity of the interface will be evaluated by comparing the emerging crack patterns, including the leaf-like fracture pattern, and the energy dissipation of the hybrid structure as predicted by the model with that measured via microscale dynamic impact tests (laser-induced projectile impact test - LIPIT) in Obj 3. Innovations in dynamic testing at microscale via the addition of Michelson interferometer will allow us to measure penetration energy of CNF-G structure and the peak out-of-plane deflection of the structure (as a measure of the peak in-plane strain) as a function of impact loading parameters and CNF arrangements, and compare that with model prediction.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 25, 2021
- Source ID
- W911NF2110096
Entities
People
- Mohammad Naraghi
Organizations
- Army Contracting Command
- Texas Engineering Experiment Station
- United States Army