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Fatigue Behavior of Unidirectional Carbon/Epoxy AFP Laminates Containing Gaps



Using automated fiber placement (AFP) provides highly repeatable and flexible manufacturing of complex and large composite components. Existence of manufacturing defects such as gaps can affect the performance of these components. In this paper, an experimental investigation was performed to study the effect of gaps on fatigue performance of AFP laminates. Tension-tension fatigue tests were conducted on unidirectional carbon/epoxy laminates containing gaps and the behavior was compared to that of base line laminates free from defects. Monitoring of damage evolution during fatigue tests was performed using infrared thermography technique. This was observed to be a powerful nondestructive technique capable of detecting the spreading of non-uniformity in structures such as induced gaps as a result of AFP manufacturing. Experimental results revealed that the effect of gaps depends on the maximum applied stress during fatigue loading. The higher is the applied stress, the higher is the reduction in fatigue life.

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