The fatigue damage in glass-fibre/MA-PP also initiates from fibre breaks or flaws, but takes locally a more tortuous crack path, and are arrested by the neighboring fibres. Replicas of fatigue crack growth in glass-fibre/MA-PP are found in Fig. 7 and Fig. 8. The cracks are on the whole more localized, scarce and smaller in size compared to the observed damage in glass-fibre/PP. The difference in fatigue damage mechanisms observed on the replica pictures for glass-fibre/PP and glass-fibre/MA-PP is schematically depicted in Fig. 9. In virtue of the stronger interface in glass-fibre/MA-PP, debonding is suppressed during fatigue, and the damage accumulation becomes more restrained and localized as indicated in the schematic picture.