Computational Analysis of Elastic Moduli of Covalently Functionalized Carbon Nanomaterials, Infinitesimal Elastostatic Deformations of Doubly Curved Laminated Shells, and Curing of Laminates

We numerically analyze three mechanics problems described below. For each problem, the developed computational model is verified by comparing computed results for example problems with those available in the literature. Effective utilization of single wall carbon nanotubes (SWCNTs) and single layer graphene sheets (SLGSs) as reinforcements in nanocomposites requires their strong binding with the surrounding matrix. An effective technique to enhance this binding is to functionalize SWCNTs and SLGSs by covalent attachment of appropriate chemical groups. However, this damages their pristine structures that may degrade their mechanical properties. Here, we delineate using molecular mechanics simulations effects of covalent functionalization on elastic moduli of these nanomaterials. It is found that Young's modulus and the shear modulus of an SWCNT (SLGS), respectively, decrease by about 34% (73%) and 43% (42%) when 20% (10%) of carbon atoms are functionalized for each of the four functional groups of different polarities studied. A shell theory that gives results close to the solution of the corresponding 3-dimensional problem depends upon the shell geometry, applied loads, and initial and boundary conditions. Here, by using a third order shear and normal deformable theory and the finite element method (FEM), we delineate for a doubly curved shell deformed statically with general tractions and subjected to different boundary conditions effects of geometric parameters on in-plane and transverse stretching and bending deformations. These results should help designers decide when to consider effects of these deformation modes for doubly curved shells. Composite laminates are usually fabricated by curing resin pre-impregnated fiber layers in an autoclave under prescribed temperature and pressure cycles. A challenge is to reduce residual stresses developed during this process and simultaneously minimize the cure cycle time. Here, we use the FEM and a genetic algorithm to find the optimal cycle parameters. It is found that in comparison to the manufacturer's recommended cycle, for a laminate with the span/thickness of 12.5, one optimal cycle reduces residual stresses by 47% and the total cure time from 5 to 4 hours, and another reduces the total cure time to 2 hours and residual stresses by 8%.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Engineering Mechanics

Department dc:contributor.department

Engineering Science and Mechanics

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2017

Author dc:creator

• Shah, Priyal

Chair dc:contributor.committeechair

• Batra, Romesh C.

Committee members dc:contributor.committeemember

• Floyd, William J.
• Hendricks, Scott L.
• Seidel, Gary D.
• Cramer, Mark S.

• Carbon nanotube
• Graphene
• Molecular mechanics
• Composite laminates
• Doubly curved shells
• Sandwich shells
• TSNDT
• Stress recovery scheme
• Cure process modeling
• Cure cycle optimization
• Genetic Algorithm

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

vt_gsexam:9751

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/77034