We present a novel type of all-aqueous non-ionic layer-by-layer films of silk fibroin with synthetic macromolecules and a natural polyphenol. We found the multilayer growth and stability to be strongly pH-dependent. Silk assembled with poly(methacrylic) and tannic acids at pH=3.5 disintegrated at pH~5; while silk/poly(N-vinylcaprolactam) interactions were stable at low and high pH values but resulting in thinner films at high pH. The results suggest that the intermolecular interactions are primary driven by hydrogen bonding with a considerable contribution of hydrophobic forces. We also demonstrated that cubical, spherical and platelet capsules with silk-containing walls can be constructed using particulate sacrificial templates. This work sets a foundation for future explorations of natural and synthetic macromolecules assemblies as biomimetic materials with tunable properties.

Loads and harmonics calculations for a wind tunnel tiltrotor model built by the U.S. Army are presented. Blade loads are calculated using the comprehensive analysis, CAMRAD II, and the multibody dynamics analysis, Dymore, for helicopter, airplane, and transition modes of flight at various velocity and pylon angles. These calculations were performed for both a gimballed hub and hingeless hub configurations. Mean variations show a primary trend along the radial station is consistent among both hub types. Half peak-to-peak comparisons show excellent agreement based on the analysis in helicopter and airplane mode. During transition flight some deviations occur within the hingeless hub type confiruation. The analytical vibratory blade loads generally match in waveforms for both the gimballed and hingeless hub configurations. Dymore and CAMRAD II show good agreement among the harmonics for both the gimballed and hingeless hub configurations with both the flapwise bending moment and chordwise bending moment cases relatively similar. Good agreement is identified particularly in airplane mode and higher flight speeds.

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This paper discusses current pretest whirl flutter predictions for the TiltRotor Aeroelastic Stability Testbed (TRAST) using two different multi-body dynamic-based rotorcraft comprehensive analysis codes, CAMRAD II and RCAS. The U.S. Army is developing this new tiltrotor system to validate whirl flutter stability analysis, a critical instability mechanism in this type of aircraft. The TRAST model has been fabricated but has not been tested in the wind tunnel. This paper includes component bench testing results with comparisons to the analysis. The predictions include parametric variations of the pitch spring and the control system geometry that can be conducted on the TRAST model.