Abstract
Ultrafast laser drilling has been proven to effectively reduce the heat-affected zone (HAZ) of carbon fiber-reinforced polymer (CFRP) composites. However, previous research mainly focused on the effects of picosecond laser parameters on CFRP drilling. Compared with a picosecond laser, a femtosecond laser can achieve higher quality CFRP drilling due to its smaller pulse width, but there are few studies on the effects of femtosecond laser parameters on CFRP drilling. Moreover, the cross-sectional taper of CFRP produced by laser drilling is very large. This paper introduces the use of the femtosecond laser to drill cylindrical holes in CFRP. The effect of laser power, rotational speed of the laser, and number of spiral passes on HAZ and ablation depth in circular laser drilling and spiral laser drilling mode was studied, respectively. It also analyzed the forming process of the drilling depth in the spiral drilling mode and studied the influence of laser energy and drilling feed depth on the holes’ diameters and the taper. The experimental results show that the cylindrical hole of CFRP with a depth-to-diameter ratio of about 3:1 (taper < 0.32°, HAZ < 10 μm) was obtained by using femtosecond laser and a spiral drilling apparatus.
Highlights
Carbon fiber reinforced polymer (CFRP) composites have the characteristics of high strength-to-weight ratio, high modulus-to-weight ratio, lower density, and good thermal stability
This paper reports the use of femtosecond lasers and spiral drilling apparatus to drill cylindrical hole in CFRP
By comprehensively considering factors such as heat-affected zone (HAZ) and drilling efficiency, this experiment selected a set of femtosecond laser and spiral laser drilling parameters to realize the processing of cylindrical holes with small HAZ
Summary
Carbon fiber reinforced polymer (CFRP) composites have the characteristics of high strength-to-weight ratio, high modulus-to-weight ratio, lower density, and good thermal stability. Salama et al [13] used a 400 W infrared picosecond laser to drill 6 mm thick CFRP and realized a HAZ < 25 μm They found that as the laser power decreases and the scanning speed increases, while the HAZ size and etching depth decrease. Yongdu Li et al [17] used a UV femtosecond laser to cut carbon fibers with a thickness of 2 mm, obtaining a HAZ of about 25 μm They used a single factor method to analyze the influence of laser average power, repetition frequency, and scanning speed on the cutting quality. The main purpose is to study the effect of laser power, rotational speed of laser, and number of spiral passes on HAZ and ablation depth in circular laser drilling and spiral drilling mode, as well as to study the influence of laser energy and drilling feed depth on the holes’ diameters and the taper in spiral drilling mode, so as to realize the drilling of cylindrical holes in CFRP with small HAZ
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