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Size Effects in Scaled Fiber Composites Under Four-Point Flexure Loading

2000; American Institute of Aeronautics and Astronautics; Volume: 38; Issue: 6 Linguagem: Inglês

10.2514/2.1066

1533-385X

David P. Johnson, J. Morton, Sotiris Kellas, Karen E. Jackson,

Fire effects on concrete materials

The effect of specimen size on the four-point flexural response of ply-level and sublaminate-level scaled composites was investigated. Two laminates were studied, namely, [+45/-45/+45/-45] s and [+45/-45/0/90] s . The material system used was AS4/3502 graphite/epoxy. Enhanced x-ray radiography and edge photomicroscopy were used to examine damage development in specimens loaded to various fractions of their ultimate load. This nondestructive examination was coupled with observations of the load/deflection response to try to correlate scaling effects with the damage development in the specimens. Results were compared to previous studies involving tensile scaling effects. It was found that the strength of ply-level scaled laminates decreased as specimen size increased, and that this effect was modeled well using the typical fracture mechanics scaling law. Sublaminate-level scaled specimens did not show a pronounced scaling effect. Although there seemed to be a slight decrease in strength with increased specimen size, the effect was small and may not be statistically significant.