Composite heat damage

Abstract

The matrix-dominated mechanical properties of heat-damaged and non-heat-damaged IM6/3501-6 laminates are presented in Part 1. Wet'' and dry'' preconditioned laminates were exposed on one side to temperatures ranging from room temperature to 750{degree}F for 0 to 60 min and subsequently tested at ambient conditions in accordance with American Society for Testing and Materials (ASTM) standards, including compression -- ASTM D3410-87, flexure -- ASTM D790-87, short-beam shear -- ASTM D2344-84, and shore-D hardness -- ASTM D2240-86. Shore-D-hardness testing was a poor indicator of mechanical strength loss. Heat-damaged 0{degree} compression specimens were the least sensitive to strength degradation compared with the other properties that were tested. Heat-damaged specimens that were tested in shear and flexure suffered significant strength reduction and degradation at exposure temperatures {ge} 550{degree}F for 5 to 60 min. The percent weight loss, micrometer measurements, and visual differences of IM6/3501-6 specimens as a function of elevated temperature exposure are reported. The results of heat-degradation effects on IM6/3501-6 specimens utilizing various nondestructive evaluation (NDE) techniques, including digital pulse (broadband), tone burst (monochromatic), ultrasonic color C scanning, and leaky'' Lamb waves are presented in Part 2. Preliminary results indicated that the leaky'' Lamb-wave technique appeared to be the most promising NDE toolmore » for characterizing the level of heat damage in IM6/3501-6 laminates. This technique is capable of detecting relative changes in a given sample at a particular location; however, it does not appear to have the capability of providing absolute results on random samples.« less