Influence of polymer properties and fiber–matrix interface on the kink band initiation in compression-compression fatigue loading of continuous fiber reinforced plastics

• Novel insight into kink banding mechanisms under fatigue loading. • Role of fatigue-creep interaction and fracture toughness for fatigue induced kink banding. • Experimental verification of previously only theoretically identified correlations. • Test methods for replicating the stress state within a kink band. Continuous fiber reinforced laminates have been investigated in much detail for their quasi-static compressive failure behavior. Numerous failure modes like fiber buckling, kink banding, delaminations and splitting are described. Kink band formation takes on a special role because this failure mode is dependent on the properties of the matrix polymer. Not many experimental results can be found on the failure modes active in compression-compression (C–C) fatigue loading of these materials. This investigation addresses for the first time the influence of the polymer properties on the C–C failure laminates with unidirectional glass- and carbon fiber reinforcement. With the aim of broadly altering the polymer properties γ radiation of a Co-60 source is used as a final specimen preparation step for an epoxy system and polycarbonate. In addition, time dependent effects are investigated by comparing quasi-static loading to two different load signals (sinusoidal and trapezoidal stress-time signal). Notched specimens are used to target kink band formation exclusively. By additional fatigue tests in in-plane shear loading and quasi-static interlaminar shear tests, it was found that the interplay between the matrix-polymer and the fiber–matrix interface could drastically alter the resulting fatigue performance of a laminate.