Compression-compression fatigue performances of hybrid unidirectional/woven carbon-fiber reinforced composite laminates after LVI.

Compression-compression fatigue behavior of hybrid unidirectional/woven carbon-fiber reinforced composite laminates after low-velocity impact (LVI) was studied in this paper. The paper contains two parts. Firstly, different levels of impact energy were introduced on the specimens. Impact damage modes were obtained and characterized as fiber breakages, matrix cracks, indentation and delamination. The relationships between indentation depth/damage area and impact energy were established. Secondly, compression-compression fatigue tests were conducted on the impact damaged specimens. Fatigue life degradation trends were analyzed and fatigue limit for different types of specimens was determined. Delamination areas by depth mode and amplitude mode of C-scan showed an increasing trend with the fatigue life increasing. Stiffness decreased sharply in the early and ending stages of fatigue life. However, stiffness exhibited stable or slightly decreasing rates in the mid-stage of fatigue life. A line-shaped failure cracks going through the impact point were observed in the fatigue failure specimens. [ABSTRACT FROM AUTHOR]