ORIGINAL ARTICLE Comprehensive investigation of surface quality and mechanical properties in CO 2 laser drilling of GFRP composites Ali Solati 1 & Mohsen Hamedi 1 & Majid Safarabadi 1 Received: 4 September 2018 /Accepted: 6 December 2018 # Springer-Verlag London Ltd., part of Springer Nature 2019 Abstract The present paper aims to study different laser drilling/cutting parameters including laser intensity, cutting speed, and gas pressure in order to achieve minimum surface roughness (R a ), heat-affected zone (HAZ), taper angle (TA), and maximum tensile strength (TS) of the laser-drilled glass fiber-reinforced plastic (GFRP) laminate. Full factorial design of experiment method and analysis of variance were adopted to investigate the effect of each parameter on the responses, and in addition, the surface roughness and tensile strength were compared with that of conventional drilling. The morphology of the laser-drilled holes was studied through the scanning electron microscopy (SEM). It was found that optimum laser drilling parameters can yield higher tensile strength and lower surface roughness in drilled GFRP laminate compared to the conventional drilling. Moreover, multi- response optimization was carried out on the results in order to obtain maximum tensile strength, minimum HAZ, minimum surface roughness, and minimum taper angle. The results revealed that the laser intensity, cutting speed, and assist gas pressure should be set at 2.04 W/cm 2 , 8 mm/s, and 4 bar, respectively, to obtain higher tensile strength and surface integrity. The results drawn from this study can be applied to improve the surface quality and mechanical properties of laser drilling of FRP materials especially in aircraft part manufacturing. Keywords Laser machining . Fiber-reinforced polymer composite . FRP . HAZ . Mechanical properties 1 Introduction Fiber-reinforced polymer materials are one of the new mate- rials which exhibit superior mechanical properties. One of the common types of fiber-reinforced plastics (FRPs) is the glass fiber-reinforced plastics (GFRPs) which were introduced in the 1940s. The glass fibers are used to improve the mechanical strength and stiffness of polymers. GFRPs due to their low cost as well as high quality are applied widely in different industries such as automobile, aerospace, sport equipment, and electronics. In addition, GFRPs have high strength-to- weight ratio among the materials with high impact resistance. Due to heterogeneity of the components in FRP materials and the non-isotropic properties, as well as contact and force presence in conventional machining, various damages are in- volved in conventional machining of GFRP workpiece includ- ing delamination, fiber pullout, fuzzing, spalling, matrix cracking, tool wear, and thermal degradation [1–7, 43]. Thus, unconventional machining methods were developed to achieve higher surface quality and less tool wear and machin- ing time. The water jet machining (WJM) [8], ultra-sonic ma- chining (USM)/vibration-assisted machining [9, 10], and laser machining [11] are the most widely used methods to perform machining on the GFRP materials. Water jet cutting can result in good surface quality but the problem with wastewater han- dling and the moisture absorbed by the GFRP which reduces the mechanical strength still remains. Moreover, in order to Highlights • CO 2 laser drilling of plain woven GFRP laminates were investigated. • Surface roughness, HAZ, and taper angle and ensile strength were studied. • Full factorial DOE was applied and ANOVA was conducted on the results. • Laser drilling can cause less drop in mechanical strength than traditional drilling. • Formation of globular chars on the surface helped to decrease the surface roughness. * Ali Solati asolati@ut.ac.ir * Mohsen Hamedi mhamedi@ut.ac.ir 1 School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran The International Journal of Advanced Manufacturing Technology https://doi.org/10.1007/s00170-018-3164-6