WEB Analysis of the effect of remote laser cutting on the damage of carbon fiber reinforced plas-tics by high-resolution computed tomographyTuesday (22.09.2020) 17:35 - 17:50 P: Processing and Synthesis 1 Part of:
As a contactless processing technology, remote-laser cutting of carbon fiber reinforced polymers (CFRP) is a promising technology to overcome the disadvantages of mechanical subtractive processing of the abrasive material. Tool wear does not occur. Since laser beam cutting is a thermal cutting process, a heat-affected zone (HAZ) inevitably occurs at the edge of the cut. However, research results show evidence that the presence of a HAZ at borehole edges can actually be beneficial. By lowering the notch stresses, the average fatigue strength of CFRP may actually increase .
The aim of the present study is to present and evaluate the damage induced to the CFRP at the cut edge by the cutting process. The remote laser beam cutting process was compared to milling as a mechanical reference process. Starting from both initial conditions, the material damage caused by cyclic mechanical stress was investigated. Two specimens with similar histories of cyclic mechanical fatigue - one remote laser cut and one milled - were examined and compared in detail. The examinations were carried out using a powerful computer tomography system, which enabled the detection of cracks and damage down to the micro-scale. Based on the results, specific damage evolution processes were identified.
A comparison of the test specimens in the finished initial state showed significant differences. As part of the HAZ, a region of vaporized matrix (MEZ) was detected at the cut edge of the remote laser-cut sample. In addition, microscopic pores formed in the interfaces between the individual layers, where they potentially caused delaminations. In contrast, milling caused singular shear fractures of the filaments. While the initial states of the cut samples showed a significant difference in damage status, these “pre-damaged” conditions did not show any evidence of different damage evolution after fatigue testing. This indicates that the HAZ caused by remote–laser cutting has no significant negative effect on the fatigue damage evolution compared to milling. The results therefore also show that a reduction in cyclic strength is not to be expected as a result of the process for a representative number of fatigue samples. The latter is the focus of ongoing work.
 Zaeh, M. F.; Byrne, G.; Stock, J. W.: Peak stress reduction in the laser contouring of CFRP. J.: CIRP Annals - Manufacturing Technology, 66(1) (2017), 249-252.