Abstract
We are here interested in the crack arrest capability under impact loading of metals and polymers used as structural and/or protection materials in aerospace engineering. Kalthoff and Winkler-type impact tests are carried out to that purpose on high strength AA7175 aluminum alloy and shock resistant polymethyl methacrylate (PMMA). Impact tests are carried out at impact velocities ranging from 50 m/s to 250 m/s and high speed camera is used to record the different steps of the failure process. For AA7175, early Mode II shear failure followed by late Mode I opening failure are seen. The premature ductile failure of the alloy is shown to result from a preceding stage of dynamic localization in the form of adiabatic shear bands. Impact tests on shock-resistant PMMA evidence the brittle feature of the material failure. It is notably shown that the higher the impact velocity (in the range 50-100 m/s) the larger the number of fragments. Moreover, depending on the impact velocity, changes in the crack path and thus in the mechanisms controlling the PMMA dynamic fracture can be seen.
Highlights
The investigation of the failure mechanisms occurring under high strain rate loading in engineering materials is a key point for the design of structures submitted to accidental overloads, as e.g. bird strike or fragment impact in the aerospace sector
In the philosophy of the crack arrest capability considered in the present work, an engineering structure is supposed to be initially weakened by a crack, resulting from e.g. fatigue loading, and the goal consists in determining the response of this pre-cracked structure to a high rate reloading
Kalthoff and Winkler (KW)-type impact tests were performed to that purpose
Summary
The investigation of the failure mechanisms occurring under high strain rate loading in engineering materials is a key point for the design of structures submitted to accidental overloads, as e.g. bird strike or fragment impact in the aerospace sector. In this context, we are here interested in the crack arrest capability under impact loading of metals and polymers used as structural and/or protection materials. Kalthoff and Winkler (KW)-type impact tests, see [1] and [2], which consist in impacting the edge of a doublenotched plate were carried out using Institut Clément Ader Lab., STIMPACT impact facility (3 gas launchers with complementary performances), see Fig., at different impact velocities comprised between 50 and 250 m/s. A Photron SA5 high speed camera was used to record the projectile/plate interaction at 105 fps (frame per second) and 320x192 pixel spatial resolution
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