The dynamic out-of-plane compressive response of E-glass composite corrugated
sandwich cores have been measured for impact velocities ranging from quasistatic to
.
Laboratory scale sandwich cores of relative density
were
manufactured from 3D woven E-glass and stitched to S2-glass face-sheets via a
double line of Kevlar yarn. Two variants of the sandwich cores were investigated:
sandwich cores with the empty spaces between the corrugations filled with a PVC
foam, and unfilled corrugations. The stresses on the rear faces of the dynamically
compressed sandwich cores were measured using a direct impact Kolsky bar. The
compression tests on both the corrugated cores and the parent strut wall material
confirmed that these relatively high relative density corrugated cores failed by
microbuckling of the strut wall material under quasistatic loading. Moreover, the
foam filling did not have any significant effect on the measured responses. The
peak stresses of both the strut wall material and corrugated cores increased
approximately linearly with strain rate for applied strain rates less than about
. This
increase was attributed to the strain rate sensitivity of the composite matrix material
that stabilised the microbuckling failure mode of the E-glass composite. At higher
applied strain rates the response was reasonably rate insensitive with compressive
crushing of the glass fibres being the dominant failure mode. A simple model
utilising the measured dynamic properties of the strut wall material accurately
predicts the measured peak strengths of the filled and unfilled corrugated
cores.
Keywords
composite lattice cores, impact testing, dynamic loads,
material rate-dependence