Honeycomb composites are finding ever increasing use on aircraft structures, making nondestructive detection of defects contained within honeycomb structures all the more important. This paper focuses on a new detection technique which makes use of the mechanical hysteresis seen as loops in the force-displacement curves. It was observed from load test data that internal damage in honeycomb sandwiches causes the average slope of the force-displacement curves to decrease and the area contained within the hysteresis loop to increase. To satisfy the inspection speed and one-sided access requirements of NDE techniques, a dynamic loading approach was pursued where an accelerometer was used to tap the surface of the test sample. Much of the research focused on the deduction of the force-displacement curves from an acceleration curve. This greatly increased the speed of the technique as well as reduced it to a one-sided test, where only access to the outer surface of the structure is needed.

I would like to dedicate this thesis firstly to my fiance, Meredith Ellis, for her patience and guidance through this process. Secondly to my parents, Tim and Kim Foreman, whom always believed in my potential, even in the hardest of times. And to my grandfather, Bill Nibbelink, who instilled in me a love for aviation at a very young age. Finally to my third grade teacher, Mrs. Overman. She provided me with hope at a time in my life when I needed it the most. I can most certainly say that this would not have been possible for me if these people had not been in my life.

No abstract

No abstract

Abstract. Porous-ceramic, thermal protection systems are used heavily in current reentry vehicles like the Orbiter, and they are currently being proposed for the next generation of US manned spacecraft, Orion. These systems insulate reentry critical components of a spacecraft against the intense thermal environments of atmospheric reentry. Additionally, these materials are highly exposed to space environment hazards like solid particle impacts. This paper discusses impact studies up to 10 km/s on 8 lb/ft 3 alumina-fiber-enhanced-thermal-barrier (AETB8) tiles coated with a toughened-unipiece-fibrousinsulation/reaction-cured-glass layer (TUFI/RCG). A semi-empirical, first principles impact model that describes projectile dispersion is described that provides excellent agreement with observations over a broad range of impact velocities, obliquities and projectile materials. Model extensions to look at the implications of greater than 10 GPa equation of state is also discussed. Predicted penetration probabilities for a vehicle visiting the International Space Station is 60% lower for orbital debris and 95% lower for meteoroids with this model compared to an energy scaled approach.