A methodology to apply constant amplitude fatigue to overcome erroneous fatigue aliasing and jitter effect is presented. A methodology to identify fatigue damage initiation and propagation in polymer adhesively bonded joints is presented. Damage initiation threshold for adhesively bonded scarf joints under fatigue is presented as (66 ± 9)% of the fatigue life. Mean strain effect under uninterrupted fatigue cycle in polymer adhesively bonded joints is presented. Variable amplitude fatigue was used for research.