Investigation on Flexural Strength Changes of Alumina Caused by Cutting using Fiber Laser

We present a comprehensive experimental study on the influence of laser cutting on the flexural strength of 0.63 mm thick alumina sheets. In this study ceramic specimens are cut to a size of 24x3 mm(2) with the flexural strength being measured using a 3 point bending test. Based on a design of experiments approach the results reveal that among the experimental parameters the laser focus position has the highest influence on the flexural strength, reducing it by 63 MPa. Cutting alumina at 300 mm/s yields a flexural strength of 395 MPa, which is significantly lower as compared with reference samples produced by scribe and break having a flexural strength of 520 MPa. Yet, a comparable flexural strength of 311 MPa using a CO2 laser is achieved at only 20 mm/s. To cut small contours, digital modulation of the fiber laser output power is employed leading to a flexural strength of 506 MPa at 1 mm/s and 469 MPa at 10 mm/s. Further results show that additional outer contours can halve the flexural strength and the lack of rounding reduces the flexural strength further. Inner contours especially with corners are also decreasing the flexural strength drastically while an inner circle causes only low strength reduction.