The effect of fiber waviness on the fatigue life of CFRP materials

• Out-of-plane waviness is a common manufacturing defect of composite materials.
• Under compressive fatigue loading it is triggering progressive damage.
• The defect geometry has a severe influence on damage modes and strength.
• A metric is established to quantitatively describe its effect on the fatigue life.

For carbon fiber reinforced polymer parts featuring manufacturing defects the balance between safety and cost has to be maintained. In this work, a non-crimp fabric with induced out-of-plane fiber waviness, which is a common defect, is investigated. Thereby its effect on the fatigue life under axial loading is assessed experimentally and numerically. For a profound understanding of damage initiation and progression, different damage modes are investigated up to final failure.A geometry based defect metric is established and the influence of this metric on the compression fatigue life of the considered material is quantitatively assessed, such that the proposed metric can be used for defining acceptance/rejection criteria for composite parts containing this specific defect.