Optimization of customized drill reamer geometrical features for aerospace composite panel

• Main Author: Jaafar, Mohd Fairuz
• Format: Thesis
• Language: English; English
• Published: 2021
• Subjects: T Technology (General); TJ Mechanical engineering and machinery
• Online Access: http://eprints.utem.edu.my/id/eprint/26072/1/Optimization%20of%20customized%20drill%20reamer%20geometrical%20features%20for%20aerospace%20composite%20panel.pdf; http://eprints.utem.edu.my/id/eprint/26072/2/Optimization%20of%20customized%20drill%20reamer%20geometrical%20features%20for%20aerospace%20composite%20panel.pdf; http://eprints.utem.edu.my/id/eprint/26072/; https://plh.utem.edu.my/cgi-bin/koha/opac-detail.pl?biblionumber=121256
• Institution: Universiti Teknikal Malaysia Melaka

Recently, carbon fibre reinforced plastic (CFRP) materials are used widely to manufacture lightweight structures. It is tailored to material properties such as high specific strength, high specific stiffness, high modulus, low weight, and high corrosion resistance and a primary option for aerospace structures. Drilling CFRP is very challenging compared to metal due to its inherent homogenous and anisotropic mechanical properties. During drilling, the typical damages that occur during drilling are delamination, pull-out fibres, fuzzing, and burrs, affecting the CFRP structure's load-carrying capacity, reducing assemblies' lifespan. Currently, multistep drilling is implemented in aircraft manufacturing to reduce delamination, which is regarded as the most critical damage that reduces mechanical parts' stiffness. However, multistep drilling required many drill types and a large number of holes in aircraft manufacturing and increased the total drilling cost per hole. The tremendous amount of holes required in aircraft manufacturing may lead to hole perpendicularity error due to lethargy and loss of concentration drilling operators. Therefore, this research aims to determine and optimize cutting tool geometrical features for drill reamer, for one-shot drilling of CFRP in various penetration angles. The machining and geometry feature performances are investigated and fabricated with a new design to obtain desired quality specifications, namely, delamination, hole wall surface roughness, hole size, and drilling thrust force in a one-shot drilling process. The multistep drilling process needs to repudiate for economical production. The parameter optimization consideration begins with parameter screening. The parameters inclusive of machining parameters and drill reamer geometrical features are investigated in various penetration angle drilling. Taguchi orthogonal array is applied for the screening phase. From eight parameters consisting of drilling angle conditions, machining parameters, and tool geometry features, only three parameters have been selected to perform optimization by response surface methodology (RSM): drilling penetration angle, second primary clearance, and helix angle. The other parameters are fixed at the best level to produce the best hole quality identified by radar chart analysis towards quality responses through the statistical analysis. In RSM, the relationship for each mentioned response was successfully developed using mathematical regression model analysis. The optimum tool geometrical features (helix angle; 4.405°, and second primary clearance; 10°) considering the maximum drilling penetration angle (5°) assigned are chosen based on the highest desirability score. The new customized drill reamer was fabricated and followed by validating experimental works that obtained less than 10% relative error compared to the prediction, which confirmed its validity. The customized tool is further investigated to reduce the drilling penetration inclination, which affirms that the quality of the hole is improved and fulfills aircraft manufacturer specifications. The hole quality in terms of delamination, hole surface roughness, hole size, and thrust force improves by about 10% from the validation trial conducted with drilling angles decreased. Undeniably, the perfect perpendicular drilling to the CFRP panel is feasible and highly recommended.