Fundamental scratch damage behavior in polymers was studied through investigation of a series of polycarbonate and polystyrene samples with different molecular weights. The constant load scratch test, based on a spherical indenter, was employed. Scanning electron microscopy and transmitted optical microscopy were performed to examine surface and subsurface damage during scratch. The plastic flow scratch pattern and the fracture scratch pattern are the two typical scratch patterns found in polymers. It is shown that shear yielding is the main mechanism for the plastic flow scratch pattern, while tensile-tear induced fracture on the surface and shear-induced fracture on the subsurface are the main damage mechanisms found in the fracture scratch pattern. The relationship between scratch resistance and material property relationship in polymers is discussed.
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