Showing papers by "Xiaoding Wei published in 2014"

Key factors limiting carbon nanotube yarn strength: exploring processing-structure-property relationships.

Abstract: Studies of carbon nanotube (CNT) based composites have been unable to translate the extraordinary load-bearing capabilities of individual CNTs to macroscale composites such as yarns. A key challenge lies in the lack of understanding of how properties of filaments and interfaces across yarn hierarchical levels govern the properties of macroscale yarns. To provide insight required to enable the development of superior CNT yarns, we investigate the fabrication–structure–mechanical property relationships among CNT yarns prepared by different techniques and employ a Monte Carlo based model to predict upper bounds on their mechanical properties. We study the correlations between different levels of alignment and porosity and yarn strengths up to 2.4 GPa. The uniqueness of this experimentally informed modeling approach is the model’s ability to predict when filament rupture or interface sliding dominates yarn failure based on constituent mechanical properties and structural organization observed experimentally. ...

In situ scanning electron microscope peeling to quantify surface energy between multiwalled carbon nanotubes and graphene.

Abstract: Understanding atomic interactions between constituents is critical to the design of high-performance nanocomposites. Here, we report an experimental–computational approach to investigate the adhesion energy between as-produced arc discharge multiwalled carbon nanotubes (MWCNTs) and graphene. An in situ scanning electron microscope (SEM) experiment is used to peel MWCNTs from graphene grown on copper foils. The force during peeling is obtained by monitoring the deflection of a cantilever. Finite element and molecular mechanics simulations are performed to assist the data analysis and interpretation of the results. A finite element analysis of the experimental configuration is employed to confirm the applicability of Kendall’s peeling model to obtain the adhesion energy. Molecular mechanics simulations are used to estimate the effective contact width at the MWCNT–graphene interface. The measured surface energy is γ = 0.20 ± 0.09 J·m–2 or γ = 0.36 ± 0.16 J·m–2, depending on the assumed conformation of the tu...

Experimental and Theoretical Studies of Fiber-Reinforced Composite Panels Subjected to Underwater Blast Loading

Abstract: Fluid–structure interaction (FSI) experiments on monolithic and sandwich composite panels were performed to identify key failure mechanisms resulting from underwater blast loading. Panel performance was compared in terms of impulse deflection. Various failure mechanisms such as delamination between laminas, matrix damage and fiber rupture in laminas, and foam crushing were identified. A 3-D rate-dependent numerical model was developed to understand the experimentally observed failure mechanisms. A new failure criterion that includes strain-rate effects was formulated and implemented to simulate different damage modes in unidirectional composite plies. This rate-dependent numerical model predicted the responses of composite panels subjected to underwater blast loading with more correlated material damage patterns with the experimental observation than previously developed models. The model also revealed the important role of the soft foam core in sandwich composite panels for improving panel performance by mitigating the transmitted impulse to the back-side face sheet while maintaining overall bending stiffness.