Bioinspired toughness improvement through soft interlayers in mineral reinforced polypropylene

•The fracture toughness of mineral reinforced PP was increased by soft interlayers.•A large inhomogeneity in Eand σY is required between the two materials.•Initial cracks are stopped by the soft interlayer.•Specimen failure occurs after crack re-initiation.•A novel plotting technique was used to depict the effects of the soft layer.