Performance demands of future unmanned air vehicles will require rapid autonomous responses to changes in environment. Towards this goal, we expect that the next generation flight control systems will include advanced sensors beyond the contemporary array. One promising scenario correlates measurements of flow footprints over aircraft surfaces with aerodynamic data to aid navigation and feedback control algorithms. As a sensor for this concept, we construct artificial hair sensors (AHSs) based on glass microfibers enveloped in an annular, radially-aligned piezoresistive carbon nanotube (CNT) forest to measure air flow in boundary layers. This study includes an analysis of the sensitivity based on laboratory scale electromechanical testing. The sensors in this work utilize nine micron diameter S2 glass fibers as the sensing mechanism for coupling to boundary layer air flows. The annular CNT forest resides in a fused silica microcapillary with electrodes at the entrance. The sensor electrical transduction mechanism relies on the resistance change of the CNT forest due to changes in both the bulk and contact resistance as a function of mechanical loading on the fiber. For the electromechanical analysis, the sensors are controllably loaded to measure both the force and moment acting at the base of the hair and the resulting deflection of the CNT forest inside of the microcapillary is measured to estimate the stress on the forest and the pressure between the forest and the electrode. The electrical responses of the sensors are compared to the mechanical state of the CNT forest. This work represents the development of a characterization tool to better understand and control the response of CNT based AHSs.

Thermal activation of shape memory polymers requires a heating mechanism that will achieve a temperature range that exceeds a minimum triggering temperature but does not overheat the material. In laboratory practice, ovens are typically used to achieve a uniform temperature during testing. In practical applications, active heating schemes must be utilized that are robust enough to handle changing environmental conditions. In this work, we analyze the intricacies of vascular heating and cooling methodologies for shape memory polymers operating in an open environment. Our methodology is based on analytical modeling of the steady state surface temperature of shape memory polymers that incorporate vascular channels. With the material properties and environmental conditions, the model is used to predict appropriate channel geometry for triggering the shape memory polymer. Thermography is used to verify the model predictions for real systems of shape memory polymers.

The primary purposes of a core in a sandwich composite are to keep the face sheets separated by a fixed distance and to transmit shear stresses. Syntactic foam cores consisting of hollow glass microspheres and resin can form strong, lightweight cores. By underfilling the interstitial space in a packed microsphere bed with a binder, a three-phase syntactic foam is created that has a percolated void network. In a sealed sandwich composite, a void network allows for the entire core of the sandwich composite to be evacuated and mechanically compressed by the exterior pressure. By combining this compression with a heating cycle, it is possible to repair core cracking and core/face sheet interface debonding when a reversible binder is used. Upon cooling, the healed sandwich restores its properties. We examine the relation between the mechanical properties of these sandwich composites and the healing methodologies.