ANALYTICAL STUDY OF A SOLAR DEGRADATION MODEL FOR THERMAL CONTROL MATERIALS AND SOME RAMIFICATIONS FOR ACCELERATED SOLAR RADIATION TESTING
Abstract
A photoreaction-diffusion model for the solar degradation of thermal control materials is mathematically formulated and analyzed. The governing differential equation for the concentration of defect specie created in the material by radiation is derived, and an analytical solution is obtained for appropriate boundary conditions. From this solution for the concentration of the ith-type defects, an analytical expression is derived for the number of ith- type defects present in a material layer of depth x and unit irradiated area. These analytical relations are used to predict the radiation-induced increase in the absorption coefficient and absorption optical thickness of a hypothetical thermal control material exposed to damaging ultraviolet irradiance equal to that of the sun. The solutions are also used to better define the environmental parameters which must be controlled during solar radiation testing of thermal control coatings. For example, the time-irradiance reciprocity principle often employed in accelerated solar testing is investigated by use of the aforementioned solutions and is found to be invalid for materials which degrade according to the photoreaction-diffusion model.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1968
- Accession Number
- AD0675140
Entities
People
- A. Matthew Smith
- A. Y. Lee
Organizations
- Arnold Engineering Development Complex