Modeling for a Small-hole Drilling Process of Engineering Plastic PEEK by Taguchi-based Neural Network Method

Engineering plastics have specific properties in the strength, hardness, impact resistance, and aging persistence, often used for structural plates and electronic components. However, the holes made by the drilling process always shrink after the cutting heat dispersion due to their high thermal expansion coefficient. Especially for small-hole fabrication, drilling parameters must be discussed thoughtfully to acquire a stable hole quality. This study developed parameter models by the Taguchi-based neural network method to save the experimental resources on drilling of engineering plastic, polyetheretherketone (PEEK). A three-level full-factorial orthogonal array experiment, L27, was first conducted for minimizing the thrust force, hole shrinkage in diameter, and roundness error. The experiments were operated by a peck-drilling process with cyclic lubricant, and the diameter was 1 mm. In terms of the network modeling, four variables were designated to the input layer neurons including the spindle speed, depth of peck-drilling, feed rate, and thrust force detected; and that of the output layer were the diameter shrinkage and roundness of the hole drilled. The models were trained by a stepped-learning procedure to expand the network’s field information stage by stage. After three stages of training, the models developed can provide precise simulations for the network’s training sets and accurately predict the hole’s characteristics for the non-trained cases.

Engineering plastic gripping mechanism for tension testing of FRP bars

A new grip adaptor, made of an engineering plastic Cast Polyamide 6 (PA6G), was developed for tension testing of FRP reinforcing bars. The new adaptor offers several advantages over conventional anchors, including the ease of application and reuse, being economical, no need for skilled labor, smaller difference between the hardness of the adaptors and sample. Bars with three different diameters (6, 8 and 12 mm), three types of fiber (Carbon, Glass and Basalt) and four types of surface texture (ribbed, wound, fine-sand coated and coarse-sand coated with widely-spaced wrapping) were tested to failure under uniaxial tension. Two identical bars were tested for each combination of parameters (fiber type, surface texture and bar diameter), one with PA6G and the other with grout-filled steel anchors. The tests indicated that the proposed method was able to ensure FRP bars to reach their tensile capacities and fail by rupture without crushing in the gripping regions and pull-out from the jaws of the testing machine. The modulus of elasticity, tensile strength and ultimate strain values of the bars with PA6G anchors were in rather close agreement with the respective values of specimens with conventional steel anchors. This close agreement, i.e. mostly a difference below 5%, implies the success of the proposed method. Among all tested bars, only the ribbed ones failed in the gripping regions in the presence of both anchors as a result of the limited contact surface (rib area), pointing out the need for the use of longer anchors for ribbed bars.

Concrete Encased with Engineering Plastics

Engineering plastic tubes are economic alternatives for the advanced composite tubing systems. The mechanical behavior of concrete-encased with engineering plastic tube (CFPT) is examined in the present study by testing short-stub CFPT columns under concentric loading. The test parameters include the plastic tube and coarse aggregate/cement ratio (a/c) ratio. Due to the low stiffness of plastic tubes, the cementitious systems have an important role to increase the stiffness of CFPT. For making concrete of consistent strength, a/c ratio is an important criterion since aggregate constitutes more than 70% of concrete. The proportion of this major component of concrete was altered in increments of 0.5 resulting in twelve mixes with a/c ratios from 3 to 8. Due to the limited test data, the mechanical performance of these structures continues to be pursued through experimental methods. The aim of the present study was to investigate experimentally the relationship between the strength of CFPT and a/c ratio which is also affected by variations in other constituent materials. The a/c ratio was the common variable in both control and CFPT specimens. The experimental results show that the ability of the engineering plastic tube in improving the load capacity of CFPT was considerably affected by the a/c ratio increment which yielded a beneficial effect on the tube confinement capacity.

Chemical recycling of poly(bisphenol A carbonate)

This review covers the current status of chemical recycling and upcycling of poly(bisphenol A carbonate), a leading engineering plastic of great economic and environmental interest.