Computer card deck subjected to end on loading in deformation apparatus, University of California, Berkeley

These chevron folds were formed by subjecting a deck of computer cards (from back in the early days of Fortran IV) to end on compression in a steel pressure vessel. The first stages of folding created asymmetrical kink folds, but with further shortening the kinks evolved into symmetrical chevrons. The folds look like the real thing, but the “rock” is of very low density.

The source is U. California, Berkeley, and as I recall the work was done by Dr. Rudy Wenk and his students.  I learned about it when I lectured at Berkeley, and when I gave a Rincon Mountains (southern Arizona) field-trip tour for Rudy and his students.  It was great fun.  I like the fact that paper can be so strong, and rocks (when viewed regionally) are so weak.  The experiment brings home the important role of flexural slip between layers, and the transition from discrete bands of kink folds to classic piles of symmetrical chevron folds. 

Age & Formation
Modern, i.e., ~1982.