Experiment research on residual compressive strength and fatigue performance of composite laminates with low velocity impact damage

Residual compressive strength and compression-compression fatigue tests of T300/QY8911 laminates with low velocity impact damage were studied. The damage characteristic of impacted laminates was measured by visual check and ultrasonic C-scan. Damage propagation in compression-compression fatigue test was measured in detail. The relationship between damage area, compressive strength after impact (CAI) and impact energy was discussed. The major damage mechanism of damaged composites under compressive or compression-compression fatigue load was also analyzed. The results show that low velocity impact damage has a great effect on the compressive strength and fatigue performance of laminates, residual compressive strength reduces by 65% when the laminates is impacted by energy of 3.75 J/mm. The damage propagation under compression-compression fatigue load can divide in two stages, on the first 60% of fatigue life, damage grows slowly; and on the rest of fatigue life, damage has a rapid growth.