An experimental study of the compression response of fluted-core composite panels with joints

Fluted-core sandwich composites consist of integral angled web members spaced between laminate facesheets, and may have the potential to provide benefits over traditional sandwich composites for certain aerospace applications. However, fabrication of large autoclave-cured fluted-core cylindrical shells with existing autoclaves will require that the shells be fabricated in segments, and joined longitudinally to form a complete barrel. Experiments on two different fluted-core longitudinal joint designs were considered in this study. In particular, jointed fluted-core-composite panels were tested in longitudinal compression because this is the primary loading condition in dry launch-vehicle barrel sections. One of the joint designs performed well in comparison with unjointed test articles, and the other joint design failed at loads approximately 14% lower than unjointed test articles. The compression-after-impact (CAI) performance of jointed fluted-core composites was also investigated with test articles that had been subjected to 6 ft-lb impacts from a 1/2-in. hemispherical indenter. It was found that such impacts reduced the load-carrying capability by 9–40%. This reduction was dependent on the joint concept.