Effects of surface quality and loading history on fatigue life of laser-machined poly(methyl methacrylate)

• Polishing of laser-machined surfaces can enhance the tensile strength up to 5%.
• Polishing can enhance fatigue life of laser-machined samples by a factor of ten.
• Loading sequence has a definite effect on the remaining life of PMMA.
• Manson–Halford and Otani–Song models can be used to estimate fatigue life of PMMA.

In this research the effects of surface quality and loading history on fatigue behavior of CO2 laser-machined poly(methyl methacrylate) are investigated. It is found that polishing of laser-machined surfaces can enhance the tensile strength up to 5% while significantly elongating the fatigue life of specimens. Microscopic observations reveal that defects on lateral laser machined surface and heat affected zone lead to a reduction of fatigue life by a factor of ten compared to samples with polished lateral surfaces. In the second part of this research it is observed that the loading sequence has a definite effect on the remaining life of poly(methyl methacrylate). Finally the ability of several cumulative damage formulations for modeling the fatigue life in multi-stage loading is evaluated, out of which Manson–Halford and Otani–Song models outperformed the others.