Andrea E. Hoyt

Light Curing Rigidizable Inflatable Wing

The objective of this study was to prove the feasibility of using light-curing resins to rigidize an inflatable wing for terrestrial and space applications. Current inflatable wings rely on the continuous presence of an inflation gas to maintain their shape. Rigidization of inflatable wings provides several potential advantages, including reducing the vulnerability to punctures, increasing stiffness and load-carrying capability, allowing a higher aspect ratio for high altitude efficiency and longer missions, and reducing weight by eliminating the make up pressurization supply. This study was a multifaceted approach that included defining operating environments for Mars survey craft and military UAVs; analyzing wing loads during deployment and rigidization as a function of internal pressure and leak rate to determine needed rigidization times; developing rapid cure resin formulations with long shelf lives; fabricating, deploying, and rigidizing a wing half-span; and testing and characterizing the rigidized wing. Results show that the wings must deploy and cure rapidly at low temperatures for some missions. The maximum time allowed for the resin to rigidize is the range in time that the inflated and unrigidized wing maintains structural integrity to fly and provide lift for the vehicle while the wing is undergoing rigidization. A series of epoxy acrylate-based resin formulations were developed that cure in 10 seconds or less at 0qC. These resins also exhibited greater than 10 year storage lifetimes in accelerated aging studies and showed mechanical properties close to thermally cured aerospace epoxies. A half-span demonstration Eppler 398 airfoil was fabricated from E-glass fabric/ATI-ROCTME37X1 resin and a polyurethane bladder. After fabrication, the wing was packed and deployed two times. The unrigidized prepreg material was very compliant and was able to be packed tightly. After the packing and deployment trials were completed, the wing was inflated to 7 psig and given a 30-minute solar cure. The rigidized wing exhibited the desired high stiffness without inflation pressure.

UV RIGIDIZABLE CARBON-REINFORCED ISOGRID INFLATABLE BOOMS

The objective of this study was to demonstrate sunlight cure (UV) of a carbon fiber-reinforced open isogrid tube for Gossamer-type spacecraft. An epoxybased resin was developed and characterized that cures in sunlight at low temperatures (10°C) on carbon and carbon/glass hybrid tows. 1.5-m-long open isogrid tubes were fabricated using wet filament winding techniques. The tubes were sunlight cured and tested for degree of cure and mechanical properties. The demonstration hardware had a 99 percent cure and showed peak buckling loads equivalent to thermally cured tubes. This technology will allow fabrication of large, lightweight and low cost inflatable Gossamer structures that have significantly improved compliant packing efficiency without degradation of deployed precision and mechanical performance.

UV rigidized carbon-reinforced isogrid boom for Gossamer applications

This work examined the feasibility of curing carbon fiber-reinforced open isogrid structures using sunlight. An orbital thermal analysis was conducted for these Gossamer structures with no insulation to determine the temperature profiles during the cure process. An epoxy-based resin was developed that showed near complete cure on carbon and hybrid carbon/glass tows and also cured at low temperatures. Demonstration hardware cured in sunlight and tested in compression to failure performed as well as similar thermally cured isogrid composites.

Light Rigidizable Inflatable Wings for UAVs

The objective of this ongoing study is to prove the feasibility of using light-curing resins to rigidize an inflatable wing for terrestrial and space applications. Current inflatable wings rely on the continuous presence of an inflation gas to maintain their shape. Rigidization of inflatable wings provides several potential advantages, including reducing the vulnerability to punctures, increasing stiffness and load-carrying capability, allowing a higher aspect ratio for high altitude efficiency and longer missions, and reducing weight by eliminating the make up pressurization supply. A previous multifaceted study included defining operating environments for Mars survey craft and military UAVs; analyzing wing loads during deployment and rigidization as a function of internal pressure and leak rate to determine needed rigidization times; developing rapid cure resin formulations with long shelf lives; fabricating, deploying, and rigidizing a wing half-span; and testing and characterizing the rigidized wing. Results show that the wings must deploy and cure rapidly at low temperatures for some missions. The maximum time allowed for the resin to rigidize is the range in time that the inflated and unrigidized wing maintains structural integrity to fly and provide lift for the vehicle while the wing is undergoing rigidization. The current work includes internal light selection for wing rigidization, evaluation of urethane acrylate resin systems, and wing design and analysis.

Polysilylene copolymers for ultrafast scintillator applications. 2. Thin film formulations

Abstract Ultrafast scintillator fluors based on poly(silylene) copolymers have been developed in our laboratory for use in fast counting applications. The absorption and fluorescence spectra of this copolymer are quite sharp compared with most aromatic fluors and result in severe reabsorption problems. This reabsorption limits the usefulness of these materials in typical host solvents for liquid or plastic scintillator formulations. However, this reabsorption does not inhibit their use as thin films and we have demonstrated thin film scintillators with neat fluor polymer that gave superior light output relative to more conventional polymeric scintillator formulations.