Effect of thermal aging on the scratch behavior of poly (methyl methacrylate)

To determine the effect of thermal aging on the scratch behavior of polymethyl methacrylate (PMMA), the scratch tests of PMMA at different aging time were conducted with the linear progression of the normal load. It was shown that the critical normal load corresponding to the surface crack decreases with the increase of aging time. The supplement indentation test and numerical simulation were conducted to identify the surface crack-initiation strength of the aged PMMA. A good correlation was found between the surface crack-initiation strength and the critical normal load. This implies that the surface crack-initiation strength could be a good criterion to measure the scratch damage of PMMA.