Survey of Current Fracture Mechanics Studies at AMMRC
ARMY MATERIALS AND MECHANICS RESEARCH CENTER WATERTOWN MA
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The status of test program on fracture behavior of unidirectionally reinforced composites using double cantilevered type specimens is reported. Material systems include S glassepoxy and graphiteepoxy. Limited fracture toughness data is available. Additionally, some effort has been initiated on cross ply specimens. A technique is developed for detection of crack initiation using an automated photographic process for recording, periodically, potential initiation sites. The observations are discussed in conjunction with damage criteria. Crack propagation studies have focussed in developing a law which accounts for the extremes of propagation rates at threshold levels of stress intensity and at the higher levels associated with unstable growth. Additionally, crack propagation experiments are described which are aimed at exploring the transient effects on crack propagation experiments are described which are aimed at exploring the transient effects on cracks propagation of sudden changes in stress intensity levels.
- Laminates and Composite Materials