Enhancement of the compressive strength of Kevlar-29/epoxy resin unidirectional composites

This paper examines the compressive and tensile strength of Kevlar-29/Derakane composites using as-received Kevlar-29 and a thermally enhanced version of the fiber. Previous studies have shown that thermal enhancement results in a form of Kevlar-29 with significantly better compressive strength at a cost of 10-20% of its tensile strength. This study compared the mechanical properties of unidirectional composites made using as-received and thermally enhanced forms of Kevlar-29 fibers. The composites made with the thermally treated fiber showed a decrease in tensile strength roughly proportional to the difference in tensile strength of the fibers. Although the improvement in the compressive strength of the composites made with the thermally treated fibers was statistically significant, it was less than anticipated. A change in predominant failure mechanism also occurred with most as-received fiber-based composites failing from a debonding/pull-out mechanism, while composites made with the thermally enhanced fiber failed primarily from microbuckling with attendant splitting.