Compressive damage in super‐thick cross‐ply composites

Abstract The compressive behavior of super‐thick composites was examined. The specimens were composed of 160 carbon/epoxy layers stacked in cross‐ply with 24 mm in thickness. A term “equivalent layer number (ELN)” is defined, representing the number of contiguous layers stacked in the same direction. Six specimen types were made with ELNs varying from 80 to 2. The results showed that the compressive strength consistently increases when the ELN is decreased. Compared with the ELN‐80, the ELN‐2 is 65% stronger. In all specimens, the initial damage was the formation of kink‐bands. However, the kink‐band growth was affected by the layup. In larger ELNs, the kink‐bands are developed in a zigzag form within the same axial group. In smaller ELNs, kink‐bands are aligned, crossing different axial groups. The damaged states were recorded in the entire loading course, allowing correlation between the damage state and the loading curve. In the final stages of loading, two modes become dominant: large‐scale delamination and long shear‐cuts. The ELN affects not only the strength but also the evolution of damage in the specimens. A smaller ELN is preferable, as the laminate becomes stronger, and the induced damage is more diversified. Highlights Super‐thick composites made and tested in compression. Smaller ELNs resulting in higher compressive strength. Larger ELNs leading to zigzag kink‐bands and large‐scale delamination. Smaller ELNs leading to aligned kink‐bands and shear‐cut failure.