ABSTRACT
The aim of the research presented in this paper was to simulate the relationship between selected technological drilling parameters (cutting speed, vc, and feed per tooth, fz) and cutting forces and the delamination in machining of a new glass-fiber-reinforced polymer (GFRP) composite. Four different types of new materials were manufactured with the use of a specially designed pressing device and differed in the fiber type (plain and twill woven materials) and weight fraction (wf) ratio, but they had the same number of layers and the same stacking sequence. A vertical machining center Avia VMC800HS was used for drilling holes with a two-edge carbide diamond coated drill. Measurements of the cutting force Fz in the drilling process conducted with variable technological parameters were carried out on a special test stand, 9257B, from Kistler. The new ink penetration method, involving covering the drilled hole surface with a colored liquid that spreads over the inner surface of the hole showing damage, was used to determine the delamination area. The cause-and-effect relationship between the drilling parameters was simulated with the use of five machine learning (ML) regression models (Linear Regression; Decision Tree Regressor; Decision Tree Regressor with Ada Boost; XGBRF Regressor; Gradient Boosting Regressor). Gradient Boosting Regressor results showed that the feed per tooth had the greatest impact on delamination-the higher the feed was, the greater the delamination became. Push-out delamination factors had higher values for materials that were made of plain woven fibers. The lowest amplitude of the cutting force component Fz was obtained for the lowest tested feed per tooth of 0.04 mm for all tested materials, with the lowest values obtained for the materials with twill fibers.
ABSTRACT
Fibers play an important role when studying the tribological behavior of reinforced friction composites. The purpose of the current research is to develop a glass fiber reinforced polymer (GFRP) recipe with improved tribological properties as well as to find the composites with the optimal tribological behavior. A ball-on-disc tribometer was used to perform dry sliding friction testing, the obtained results were then analyzed with the ELECTRE (ELimination Et Choix Traduisant la REalite-elimination and choice translating the reality) method based on a utility matrix having process parameters the applied load, sliding velocity, and weight percentage of the fiber content. The ELECTRE method was chosen to find the optimal tribological parameters, with respect to more performance criteria, because it is one of the best multiple criteria decision-making methods. The optimal combination of parameters for the multi-response characteristics of the investigated friction composite was at an applied load of 10 N, a sliding velocity of 0.1 ms-1 and a 54% weight fiber content. The results showed that the addition of glass fiber (GF) content did not considerably improve the tribological behavior of the friction composites. In addition, from the nano focus-optical 3D scanning electron microscopy, images of the friction, tested friction and wear composites, plate formation, fiber-matrix delamination, fiber pull-out, and matrix cracking and damage, various wear mechanisms were identified.
ABSTRACT
Tribo-mechanical experiments were performed on Glass Fiber Reinforced Polymer (GRFP) composites against different engineering materials, and the tribological behavior of these materials under dry conditions was investigated. The novelty of this study consists of the investigation of the tribomechanical properties of a customized GFRP/epoxy composite, different from those identified in the literature. The investigated material in the work is composed of 270 g/m2 fiberglass twill fabric/epoxy matrix. It was manufactured by the vacuum bag method and autoclave curing procedure. The goal was to define the tribo-mechanical characteristics of a 68.5% weight fraction ratio (wf) of GFRP composites in relation to the different categories of plastic materials, alloyed steel, and technical ceramics. The properties of the material, including ultimate tensile strength, Young's modulus of elasticity, elastic strain, and impact strength of the GFPR, were determined through standard tests. The friction coefficients were obtained using a modified pin-on-disc tribometer using sliding speeds ranging from 0.1 to 0.36 m s-1, load 20 N, and different counter face balls from Polytetrafluoroethylene (PTFE), Polyamide (Torlon), 52,100 Chrome Alloy Steel, 440 Stainless Steel, and Ceramic Al2O3, with 12.7 mm in diameter, in dry conditions. These are commonly used as ball and roller bearings in industry and for a variety of automotive applications. To evaluate the wear mechanisms, the worm surfaces were examined and investigated by a Nano Focus-Optical 3D Microscopy, which uses cutting-edge µsurf technology to provide highly accurate 3D measurements of surfaces. The obtained results constitute an important database for the tribo-mechanical behavior of this engineering GFRP composite material.
ABSTRACT
This paper reports the results of measurements of cutting forces and delamination in drilling of Glass-Fiber-Reinforced Polymer (GFRP) composites. Four different types of GFRP composites were tested, made by a different manufacturing method and had a different fiber type, weight fraction (wf) ratio, number of layers, but the same stacking sequence. GFRP samples were made using two technologies: a novel method based on the use of a specially designed pressing device and hand lay-up and vacuum bag technology process. The study was conducted with variable technological parameters: cutting speed vc and feed per tooth fz. The two-edge carbide diamond-coated drill produced by Seco Company was used in the experiments. Cutting-force components and delamination factor were measured in the experiments, and photos of the holes were taken to determine the delamination. In addition, modeling of cause-and-effect relationships between the technological drilling parameters vc and fz was simulated with the use of artificial neural network modeling. For all tested GFRP materials, an increase in fz led to an increase in the amplitude of cutting-force component Fz. The lowest values of the amplitude of cutting-force component Fz were obtained with the lowest tested feed per tooth value of 0.04 mm/tooth for all tested materials. It was observed that materials produced with the use of the specially designed pressing device were characterized by lower values of the cutting-force component Fz. It was also found that the delamination factor increased with an increase in fz for all tested GFRP materials. A comparison of the lowest and the highest values of fz revealed that the lowest delamination factor increase was archived by the B1 material and amounted to about 12.5%. The error margin of the obtained numerical modeling results does not exceed 15%, so it can be concluded that artificial neural networks are a suitable tool for modeling cutting force amplitudes as a function of vc and fz. The study has shown that the use of the special pressing device during the manufacturing of composite materials has a positive effect on delamination.
ABSTRACT
Composite materials are very often used in the manufacture of lightweight parts in the automotive industry, manufacturing of cost-efficient elements implies proper technology combined with a structural optimization of the material structure. The paper presents the manufacturing process, experimental and numerical analyses of the mechanical behavior for two composite hoods with different design concepts and material layouts as body components of a small electric vehicle. The first model follows the black metal design and the second one is based on the composite design concept. Manufacturing steps and full details regarding the fabrication process are delivered in the paper. Static stiffness and strain values for lateral, longitudinal and torsional loading cases were investigated. The first composite hood is 254 times lighter than a similar steel hood and the second hood concept is 22% lighter than the first one. The improvement in terms of lateral stiffness for composite hoods about a similar steel hood is for the black metal design concept about 80% and 157% for the hood with a sandwich structure and modified backside frame. Transversal stiffness is few times higher for both composite hoods while the torsional stiffness has an increase of 62% compared to a similar steel hood.
ABSTRACT
The paper presents the manufacturing technology for a material obtained from glass fiber waste, quartz sand, and polyester binder, used for ornamental building plates. The composite has a cover surface that ensures protection of the material from environment attacks and a structural material that can be subjected to chemical degradation. The mechanical properties of the obtained material were experimentally investigated through compressive mechanical tests. To observe the material's behavior in contact with external agents (rain or acid rain, due to environmental pollution), analyses were performed in laboratory conditions. An investigation on the effects of chemical attack substances was conducted. SEM and macroscopic analyses were performed, and the surface roughness was determined for each sample area. The obtained results were statistically analyzed and showed that there is no significant difference between the surface roughness for treated and untreated samples. Furthermore, the surfaces were analyzed by X-ray diffraction and mineralogical optical microscopy in polarized light with crossed nicols. It was observed that rainwater does not affect the plate structure even if the plates are used in high-pollution environments. The material is suitable for exterior building walls from the point of view of chemical attack and resistance.
ABSTRACT
Fibre-reinforced polymers (FRP) have attracted much interest within many industrial fields where the use of 3D printed molds can provide significant cost and time savings in the production of composite tooling. Within this paper, a novel method for the manufacture of complex-shaped FRP parts has been proposed. This paper features a new design of bike saddle, which was manufactured through the use of molds created by fused deposition modeling (FDM), of which two 3D printable materials were selected, polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS), and these molds were then chemically and thermally treated. The novel bike saddles were fabricated using carbon fiber-reinforced polymer (CFRP), by vacuum bag technology and oven curing, utilizing additive manufactured (AM) molds. Following manufacture the molded parts were subjected to a quality inspection, using non-contact three-dimensional (3D) scanning techniques, where the results were then statistically analyzed. The statistically analyzed results state that the main deviations between the CAD model and the manufactured CFRP parts were within the range of ±1 mm. Additionally, the weight of the upper part of the saddles was found to be 42 grams. The novel method is primarily intended to be used for customized products using CFRPs.