Browsing by Subject "Resins"

Now showing 1 - 3 of 3

Open Access
Development of an iterative learning controller for polymer based micro-stereolithography prototyping systems
(IEEE, 2016) Türeyen, Erkan Buğra; Karpat, Yiğit; Çakmakcı, Melih
Additive manufacturing has become increasingly popular for a wide range of applications in recent years. Micro-stereolithography (μSLA) is a popular method for obtaining polymer-based parts. Systems using the μSLA approach usually consist of a vertical positioning system, a light source and a container where the component is built gradually as the polymer is cured at the locations where the ultraviolet light is projected. It has been noted that the motion of the positioning system and the intensity of the light source is an important factor to achieve high level dimensional precision. In this paper a three dimensional error based learning scheme is presented to improve the time varying process parameters of the system so that the dimensional accuracy of the product is improved. A mathematical model of the curing process is used for developing the error based learning algorithm. The current process parameters as a function of time and the dimensional error obtained at each layer of the production are used for increasing the quality and precision of the same part in the next iteration. Our initial simulation results show significant improvements can be obtained in a few iterations if the correct learning parameters are used based on the target parts dimensional properties.
Embargo
Eugenol-derived bio-benzoxazine resins: synthesis, characterization, and exceptional thermal stability
(John Wiley & Sons, Inc., 2024-06-20) Doğan, Yelda Ertaş; Uyar, Tamer
In this study, we succesfully synthesized bio-benzoxazine resins using eugenol, a bio-based phenolic compound, in combination with three distinct functional amines: ethanamine, aniline, and hexane-1,6-diamine. Characterization of the resulting bio-benzoxazine resins, namely E-ea (eugenol, ethanamine), E-a (eugenol, aniline), and E-dh (eugenol, hexane-1,6-diamine), was performed through H-1 NMR spectroscopy, FTIR spectroscopy, high-resolution mass spectrometry, and elemental analysis. Thermal properties were investigated using thermogravimetric analysis (TGA) for both the eugenol-derived bio-benzoxazines (E-ea, E-a, E-dh) and their corresponding polybenzoxazines (PE-ea, PE-a, PE-dh). Notably, all eugenol-based polybenzoxazines exhibited excellent thermal stability with very similar characteristics. Our findings suggest that the presence of allyl groups in eugenol promoted a more cross-linked network structure compared to other functional groups on amines. As a result, eugenol-derived bio-benzoxazines demonstrated superior thermal properties, illustrated by their impressive char yields: PE-ea; 45.6%, PE-a; 45.1%, and PE-dh; 44.1%.
Open Access
Heat-damage assessment of carbon-fiber-reinforced polymer composites by diffuse reflectance infrared spectroscopy
(John Wiley & Sons, Inc., 2005) Dara, I. H.; Ankara, A.; Akovali, G.; Süzer, Şefik
Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was used to assess the effects of heat damage on carbon-fiber-reinforced polymer composites. Moisture-saturated graphite-epoxy laminates with a quasi-isotropic lay-up were heat-damaged above their upper service temperatures. The loss of matrix-dominated mechanical properties due to heat exposure was investigated in the laboratory under environmental testing conditions with mechanical tests, ultrasonic C-scanning, and DRIFT spectroscopy. The reduction of the mechanical strength of the composite materials was accompanied by an increase in the carbonyl band integral and a decrease in the phenyl ratio and hydroxyl and hydrocarbon band integrals, as shown by the DRIFT spectra. DRIFT was confirmed to be more effective than ultrasonic inspection in evaluating the extent of heat damage, and a good correlation was found between the mechanical test results and DRIFT spectra. © 2005 Wiley Periodicals, Inc.