Effect of Heat, Loading, and Moisture on the Durability of Fiber Composites

The purpose of this report is to describe the results of a program to determine how fiber composite materials behave when subjected to a combination of heat, moisture, and shear loads. A feature of the program was the design of a relatively simple fixture for uniformaly applying a shear stress to fiber composite specimens by short beam flexure. In the current program, various fiber composites have been subjected to the temperature of 50-55°C, immersion in deionized water, and a load initially equal to roughly one-half the load that would cause shear failure at room temperature. Heat, loading, and moisture each have a deleterious effect on the durability of fiber composites. But no synergism of moisture and load was found in which the degradation of strength was greater than the sum of the individual effects.