Characterization of Impact Damage Resistance of CF/PEEK and CF/Toughened Epoxy Laminates under Low and High Velocity Impact Tests

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Abstract
In order to use composite materials in aeronautical turbo engines, their resistance to impact damage must be understood. In this work the subperforation flat-wise impact resistance of three kinds of high resistance material systems were evaluated under low and high velocity impact tests. Tested systems were AS4/PEEK (APC-2/AS4, ICI-Fiberite), AS4/PEEK + IL, which consists of APC-2 prepreg and PEEK film inserted between layers as an interleave, and toughened epoxy system T800/#3900 (Toray). To investigate the effects of stacking sequence on resistance, three lay-ups (0/ + 30/0/ -30)s, (0/ + 60/0/ -60)s, and (0/ + 45/90/ -45)s-were tested. A drop weight system was used for the low velocity tests, where the velocity ranged from 1.5 to 3.1 m/s. An air gun system was used for the high velocity tests, where the velocity range was between 50 and 100 m/s. Both velocity impact tests used the same specimens geometries, support structures, impactor head geometries, and incident energy range. The projected damage area was measured with an ultrasonic C-Scan. The relation between damage area (DA) and impact energy (IE) was linear, and the ratio of the DA/IE quantified the impact resistance of each specimen. The value of DA/IE for the high velocity tests was larger than the value for low velocity tests. To estimate the lay-up effect, a stacking parameter,B, which indicates the difference of the inplane stiffness between the adjacent laminae, was proposed. A proportional relation between the DA/IE and the f was obtained. The value of (DA/IE)/3, which was independent of stacking sequence, indicated the impact resistance of the tested material systems for both velocity levels. The ratio of (DA/IE)/3 for the high velocity to the value for the low velocity changed with material systems.