Static and Dynamic Strength of Scarf-Repaired Thick-Section Composite Plates

Report No. ARL-CR-549
Authors: Bazle A. Gama, Stephane Mahdi, Curt Cichanowski, Shridhar Yarlagadda, and John W. Gillespie, Jr.
Date/Pages: September 2004; 38 pages
Abstract: Composite structural armor is typically a sandwich construction consisting of thick-section composite, rubber, and ceramic layers, which are combined to provide an optimal balance of structural and ballistic performance at minimum weight. Our focus was on the scarf repair of the thick-section plain weave S-2 Glass/SC15 composite subjected to static and dynamic loading. Deliberate damage to backing plates was repaired at elevated temperatures using induction heating and at room temperature. The static response of control and repaired plates was compared via four-point bend testing. The effect of three scarf angles and four repair adhesives was quantified. Using these repair techniques, renewal of stiffness was achievable, except for the case of the highly ductile, low-stiffness adhesive. The renewal of moment capacity of the repair beams was highly dependent on the scarf angle for various adhesives, and a maximum renewal of strength was 60%. The dynamic strength of scarf patch-repaired composite specimens was investigated through axial compression strength testing using a split-Hopkinson bar. Under dynamic loading, the axial strength was found to be dependent on the scarf angle and rate of loading. Loci of failure are reported for the various materials, scarf angles, and loading conditions.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2004