Engineering applications with complex composite structures like hat stringerstiffened flat panels when subject to impact result in a varying degree of damage,damage behavior, and loading paths compared to traditional composite panels. Thesedifferences are investigated in a co-cured stiffened T800/3900-2 carbon/epoxylaminate by subjecting it to low velocity impacts with varying impactor tip radii (12.7and 76.2 mm), impact location (edge and center of stringer flange), and impact type(metal versus rubber protected). For all cases, the damage response is quantified(force time history and delamination area) and the energy is held constant at nominally90 J. Impact of the 5 kg pendulum head occurs at 5 m/s.It is shown that the onset of delamination and the delamination area areindependent of the impactor radius in the stringer stiffened panels. Similarly, the forcetime histories at a given site are independent of the tip radii (e.g. both 12.7 and 76.2mm striking the center of the stringer/panel interface had similar force response). Theforce time history results show that the contact force at the center of the stringer ishigher than that at the edge due to the added stiffness of the stringer and panelinterface. The impactors fitted with rubber tips reduces the contact force levels by upto 15% and 8% at the center and edge of the stinger, respectively.Finite element simulation of the 12.7 mm radius tip at the edge of thestringer/panel interface were validated with the experimental data usingABAQUS/Explicit.
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