Composite Repairs of Cracked Metallic Airframe Structures
Final rept. Oct 1990-Feb 1992
KNOWLEDGE SCIENCES INC ATLANTA GA
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This report summarizes work that quantifies the benefits of composite patch repairs on cracked metallic aircraft structures. The first chapter describes a data base on bonding methods and repair materials that can be used in design and analysis. In the second chapter, analytical models are derived for the stress intensity factor of cracks in metallic sheets with bonded orthotropic repairs. Specific configurations included through-the-thickness center cracks, through-the-thickness cracks at a loaded fastener hole, surface cracks, and surface cracks at a hole. These analyses can be used in calculations of crack growth life extension resulting from the bonded repairs. Four types of specimens were tested in fatigue to verify the increase in fatigue life. The four configurations were edge crack specimens, surface specimens with multiple site damage MSD.