G. Caprino et al., Influence of material thickness on the response of carbon-fabric/epoxy panels to low velocity impact, COMP SCI T, 59(15), 1999, pp. 2279-2286
Low velocity impact tests were carried out on carbon-fabric/epoxy laminates
of different thicknesses, by means of a hemispherical impactor. The force
and absorbed energy at the point of delamination initiation, the maximum fo
rce and related energy, and penetration energy were evaluated. From the exp
erimental results, all these quantities, except the energy for delamination
initiation, followed the same trend, increasing to the power of approximat
ely 1.5 with increasing plate thickness. For what concerns the force at del
amination initiation, it is shown that its trend agrees with the assumption
of a Hertzian contact law, coupled with the hypothesis that only the shear
stress is responsible for delamination. It is also demonstrated that the f
orce/displacement curves recorded for the different thicknesses sensibly su
perpose with each other when the forces are scaled to the power 1.5 and the
displacements are held unchanged. This explains the observed dependence of
the maximum force, energy at maximum force, and penetration energy on the
thickness. Finally, the energy at delamination initiation is calculated by
an analytical model, assuming that the total energy is shared in two parts,
one of which is stored in flexure, and the other in the material volume cl
ose to the contact zone. (C) 1999 Elsevier Science Ltd. All rights reserved
.