When holes are produced on carbon fiber reinforced plastic (CFRP) laminates, in particular for the aerospace and automotive industries, special attention should be focused on as the machining parameters influencing the damage. In this study special drill bits and high-speed cutting (HSC) are used and compared with conventional cutting conditions. The digital image of the damage was conducted in order to analyze the delamination when two composite boards were drilled simultaneously. The experimental results indicated that the use of HSC in drilling is suitable to reduce the damages produced in CFRP with material removal rate increasing considerably.

In the vacuum thermoforming process, the group effects of the processing parameters, when related to the minimizing of the product deviations set, have conflicting and non-linear values which make their mathematical modelling complex and multi-objective. Therefore, this work developed models of prediction and optimization using artificial neural networks (ANN), having the processing parameters set as the networks’ inputs and the deviations group as the outputs and, furthermore, an objective function of deviation minimization. For the ANN data, samples were produced in experimental tests of a product standard in polystyrene, through a fractional factorial design (2^k-p). Preliminary computational studies were carried out with various ANN structures and configurations with the test data until reaching satisfactory models and, afterwards, multi-criteria optimization models were developed. The validation tests were developed with the models’ predictions and solutions showed that the estimates for them have prediction errors within the limit of values found in the samples produced. Thus, it was demonstrated that, within certain limits, the ANN models are valid to model the vacuum thermoforming process using multiple parameters for the input and objective, by means of reduced data quantity.

Polymeric materials have been widely used to replace traditional metallic materials due to their high specific elastic properties. Even though polymeric materials can be produced as near net shapes, machining is still required to make the assembling of the final products. The selection of tool and cutting conditions is very important to machine plastics because of the high ductility and low melting point of the materials. In this study, the machining behaviour of high-performance engineering polymers, such as ultra-high-molecular-weight polyethylene, polyoxymethylene and polytetrafluoroethylene, has been investigated using a full-factorial design (design of experiment). The effect of the factors such as feed speed, spindle speed and drill point angle was identified for each of the response variables (circularity error, surface roughness (R_a) and thrust force (F_f)). The drilling mechanism was substantially affected by the physical and mechanical properties of the polymers. Different cutting set-up conditions were able to optimize the responses. The polytetrafluoroethylene exhibited better results, achieving lower circularity error, surface roughness and thrust force. In the opposite manner, the ultra-high-molecular-weight polyethylene exhibited a rough topography at low feed rate and spindle speed levels.

Composite materials are widely employed in the naval, aerospace and transportation industries owing to the combination of being lightweight and having a high modulus of elasticity, strength and stiffness. Drilling is an operation generally used in composite materials to assemble the final product. Damages such as the burr at the drill entrance and exit, geometric deviations and delamination are typically found in composites subjected to drilling. Drills with special geometries and pilot holes are alternatives used to improve hole quality as well as to increase tool life. The present study is focused on the drilling of a sandwich composite material (two external aluminum plates bound to a polyethylene core). In order to minimize thrust force and burr height, the influence of drill geometry, the pilot hole and the cutting parameters was assessed. Thrust force and burr height values were collected and used to perform an analysis of variance. The results indicated that the tool and the cutting speed were the parameters with more weight on the thrust force and for burr height they were the tool and the interaction between tool and feed. The results indicated that drilling with a pilot hole of Ø4 mm exhibited the best performance with regard to thrust force but facilitated plastic deformation, thus leading to the elevation of burr height, while the lowest burr height was obtained using the Brad and Spur drill geometry.

Fiber-reinforced composites are widely recognized for their superior mechanical properties and advantages for applications in aerospace, defence and transportation sectors. Delamination is a problem associated with drilling fiber-reinforced composite materials. In this work, the effects of feed speed, rotational speed and drill geometry on the resulting delamination factor are comparable in spite of the drill point angle used. A mathematical model is proposed to predict delamination in drilling glass fiber-reinforced plastic composites.