The Effects of Moisture on Fracture Toughness and Thermal Relaxation of Stretched Acrylic Plastics,
NAVAL RESEARCH LAB WASHINGTON DC
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Studies were conducted to determine the effects of absorbed moisture on the thermal relaxation behavior and fracture toughness of stretched acrylic plastic. Results indicated that the thermal relaxation behavior is affected significantly by the amount of absorbed moisture. Test results can be obtained on the same material that meet or do not meet. The requirements of that specification, depending on the moisture content of the test specimens. Fracture toughness tests were conducted over a range of loading rates and for different moisture contents, using the compact tension specimen. The material with a high moisture content had a higher fracture toughness than dry material at lower rates of loading. At high loading rates, moisture content did not affect fracture toughness. Thus, if a specification stipulates a high loading rate for the fracture toughness test, control of moisture content is not necessary. Data previously obtained on polycarbonate plastic indicates that this material has a higher fracture toughness than stretched acrylic for lower moisture contents. However, at high moisture contents, there is little difference between the two materials for the thicknesses and loading rates studied.