Compressive fatigue behavior of low velocity impacted and quasi-static indented CFRP laminates

The compression fatigue behaviors of CFRP laminates with impacted or quasi-static indented damage for two material systems, CCF300/QY9511 and CCF300/5428, were compared in this paper. The same surface damages, characterized by dent depth, were induced by low velocity impact (LVI) or quasi-static indentation (QSI) tests for the CFRP laminates. Using visual observation, C-Scan and thermal de-ply experimental measure methods, the surface damage and internal delamination of the specimens are described in detail to provide more information to understand the mechanical behaviors of impacted or quasi-static indented CFRP laminates. Static tests and staircase fatigue tests were performed to obtain the static compressive strength and compressive fatigue strength. The experimental outcomes show that the compressive fatigue strength of the quasi-static indented specimens is obviously greater than that of impacted specimens, while the specimens with quasi-static indented damages have a similar static compressive strength as those with impacted damages, for both material systems. Using QSI-induced damage to replace LVI-induced damage provides a roughly equivalent strength evaluation in static compression tests but exaggerates fatigue strength estimation in compression fatigue tests.