Composite materials with carbon nanotube and graphene additives have long been considered as exciting prospects among nanotechnology applications. However, after nearly two decades of work in the area, questions remain about the practical impact of nanotube and graphene composites. This uncertainty stems from factors that include poor load transfer, interfacial engineering, dispersion, and viscosity-related issues that lead to processing challenges in such nanocomposites. Moreover, there has been little effort to identify selection rules for the use of nanotubes or graphene in composite matrices for specific applications. This review is a critical look at the status of composites for developing high-strength, low-density, high-conductivity materials with nanotubes or graphene. An outlook of the different approaches that can lead to practically useful nanotube and graphene composites is presented, pointing out the challenges and opportunities that exist in the field.

The effect of strain on the phonon modes of monolayer and few-layer MoS${}_2$ has been investigated by observing the strain-induced shifts of the Raman-active modes. Uniaxial strain was applied to a sample of thin-layer MoS${}_2$ sandwiched between two layers of optically transparent polymer. The resulting band shifts of the $E_{2g}^1$ ($\sim$ $385.3{\mathrm{cm}}^{-1}$) and $A_{1g}$ ($\sim$ $402.4{\mathrm{cm}}^{-1}$) Raman modes were found to be small but observable. First-principles plane-wave calculations based on density functional perturbation theory were used to determine the Grüneisen parameters for the $E_{1g}$, $E_{2g}^1$, $A_{1g}$, and $A_{2u}$ modes and predict the experimentally observed band shifts for the monolayer material. The polymer–MoS${}_2$ interface is found to remain intact through several strain cycles. As an emerging 2D material with potential in future nanoelectronics, these results have important consequences for the incorporation of thin-layer MoS${}_2$ into devices.