Compression Fatigue of Impact Damaged Graphite Epoxy Sandwich Beams

摘要

The resistance of composite aircraft structures to handling and impact loadings is an important consideration in assessing their suitability for long term operational service. The specific threat addressed in this study is that of low speed (0 to 30m/s), hard object, transverse normal impact (dropped tool, runway stones, etc.). The objective is to characterize the damage which occurs to composite faced sandwich structures under realistic impact conditions and determine the effect of this damage on residual compression fatigue properties. The sandwich construction selected for study consisted of AS/3501-6 graphite/epoxy face sheets of (0/+ OR - 45/0) SUBS CONSTRUCTION BONDED TO HRP-3/16-5.5 honeycomb core. This construction is representative of sandwich construction generally used in flaps, spoilers, and access doors. Static indentation tests were conducted on sandwich panels supported on a rigid foundation, and dropped weight impact tests were performed on simply supported sandwich beams. Comparison of the results of these tests indicates that static tests in conjunction with a simple 2-degree-of-freedom dynamic model can be used to accurately simulate low velocity, hard object impacts on sandwich structures for impact velocities up to 6.1 m/s. Test results of indentation versus static load is used in the dynamic model to predict the indentation which would occur for any particular impact case.