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Accession Number N20130013421
Title Normalization of Impact Energy by Laminate Thickness for Compression After Impact Testing.
Publication Date Apr 2013
Media Count 52p
Personal Author A. T. Nettles S. M. Hromisin
Abstract The amount of impact energy used to damage a composite laminate is a critical parameter when assessing residual strength properties. The compression after impact (CAI) strength of impacted laminates is dependent upon how thick the laminate is and this has traditionally been accounted for by normalizing (dividing) the impact energy by the laminate's thickness. However, when comparing CAI strength values for a given lay-up sequence and fiber/resin system, dividing the impact energy by the specimen thickness has been noted by the author to give higher CAI strength values for thicker laminates. A study was thus undertaken to assess the comparability of CAI strength data by normalizing the impact energy by the specimen thickness raised to a power to account for the higher strength of thicker laminates. One set of data from the literature and two generated in this study were analyzed by dividing the impact energy by the specimen thickness to the 1, 1.5, 2, and 2.5 powers. Results show that as laminate thickness and damage severity decreased, the value which the laminate thickness needs to be raised to in order to yield more comparable CAI data increases.
Keywords Comparison
Compression loads
Graphite-epoxy composites
Impact strength
Impact tests
Impact tolerances
Mechanical properties

Source Agency National Aeronautics and Space Administration
NTIS Subject Category 71F - Composite Materials
41K - Engineering Materials
Corporate Author National Aeronautics and Space Administration, Huntsville, AL. George C. Marshall Space Flight Center.
Document Type Technical report
Title Note N/A
NTIS Issue Number 1323
Contract Number N/A

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