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The Use of Expanding Monomers in Embedding and Related Processes
Published in Rajender K. Sadhir, Russell M. Luck, Expanding Monomers, 2020
A critical component in many high voltage electrical equipment applications is the stand-off insulator. These insulators are often cast from a highly filled epoxy resin system and surround a metallic conductor which passes through the center of the casting. These insulators are under high electrical stress, typically up to 100 kV rms/in. for continuous operation and up to 350kV peak/in. during impulse tests. Reliability problems can sometimes arise with such insulators, when puncturing can occur during impulse testing or during field operation. Such internal breakdowns are the result of impurity inclusions or voids in the case resin system. The voids can occur either in the bulk or at the interface with the metallic insets. Such voids arise because of shrinkage of the epoxy during cure or upon aging, or because of differential thermal expansion between the metal and the epoxy resin casting system. The impurity inclusions can be eliminated or drastically reduced by improved processing, while the effects of differential thermal expansion can be in large part overcome by the judicious selection of fillers for the epoxy resin system to match the thermal coefficient of expansion of the metallic inserts. However, shrinkage effects due to cure and aging of the epoxy resin cannot be overcome with conventional epoxy resin technology, so Sadhir and Saunders examined the effect of addition of NSOC expanding monomer to a typical epoxy standoff insulator formulation, given in Table 10.
Saving a project through Rapid Manufacture in South Africa
Published in Paulo Jorge Bártolo, Artur Jorge Mateus, Fernando da Conceição Batista, Henrique Amorim Almeida, João Manuel Matias, Joel Correia Vasco, Jorge Brites Gaspar, Mário António Correia, Nuno Carpinteiro André, Nuno Fernandes Alves, Paulo Parente Novo, Pedro Gonçalves Martinho, Rui Adriano Carvalho, Virtual and Rapid Manufacturing, 2007
The tool maker quoted them R 62 700 (approximately € 6 500) for the tooling of a sensor housing and R85 000 (approximately € 9 000) for the enclosure they wanted. If the sensor housing could be redesigned in such a way that no sliding cores would be needed to manufacture this, the cost of the tooling could come down. CountPro needed six different designs. With the high tooling cost however, they had to cut down on their designs. In reality this is not too expensive but for this start-up company it is impossible to pay such amounts for the tooling and still be able to produce the printed circuit boards etc., needed for their product. Therefore they had to find a cheaper way to develop their product and to get it installed in the vehicles. The taxi market is big enough to spend these amounts of money on the tools. The South African government embarked on a recapitalization program whereby they buy the old taxis from their owners for a prescribed amount and supply new larger taxis at a competitive price to the owners. The old taxis are destroyed to get them of the roads. This is a drive to try and get the un-road worthy and lapidated taxis off the road. The government is trying to replace these normal mini bus-type taxis with larger taxis that can take more passengers at a time. Due to this whole process, CountPro is not sure when the taxis will be replaced and what technology will be in them, so they need to get their device into existing taxis as fast as possible to capture the market while it still exists. There is a good chance that this will be needed in the new taxis also, but no one is sure as yet. Figure 1 shows the original sensor cover, which was manufactured by means of resin casting. As can be seen from the pictures the product’s appearance is very bad and one cannot sell it as a professional product.
Dynamic analysis of spinning triangle geometry part 1: validation of methodology
Published in The Journal of The Textile Institute, 2019
Noman Haleem, Stuart Gordon, Xin Liu, Christopher Hurren, Xungai Wang
For resin casting process, a circular mould was developed from a machined acrylic tube (27.5 mm ID/32 mm OD). An aerosol-based universal mould release agent (Smooth-on, Macungie, PA, USA) was applied inside the mould to enable easy extraction of the rubber cot after curing. The base tube and mould (for the rubber cot) were fixed on a plastic plate in a concentric arrangement in order to pour the resin into the rubber cots as shown in Figure 2. The Clear flex 95, a two-part based resin system, was used at a mix ratio of 1:1.5 (by weight) of part A and part B, respectively. The resin processing was initiated by separately degassing 10 g of part A and 15 g of part B. The degassing was carried out for 10 min for each part in a vacuum chamber at negative pressure of 15 inches of mercury. After degassing separately, both parts were thoroughly mixed with each other and degassed again for 15 min to remove any air bubbles out of the mixture. The complete removal of air bubbles was critical to achieve the desired level of clarity in the roller.
Improved adhesion between nickel–titanium SMA and polymer matrix via acid treatment and nano-silica particles coating
Published in Advanced Composite Materials, 2018
Bin Yang, Yongchao Zhang, Fu-Zhen Xuan, Biao Xiao, Liang He, Yang Gao
Single fiber pull-our test was performed to evaluate the interfacial performance between modified SMA wire and epoxy resin. To embed SMA wire into epoxy resin, a silica gel mold with cylindrical holes (depth and diameter are 2 mm, respectively) was prepared. After the resin was cured, the specimens with SMA wire located in the center could be demould. The cure duration of resin is 24 h at room temperature. Before pull-out test, fundamental mechanical performance of components including SMA wire and epoxy resin casting was tested. Calibrating length of SMA wire in tensile test was 40 mm, and the tested SMA wire was the initial material without any treatment. Epoxy casts were prepared by casting process. Epoxy resin, hardening agent, and accelerating agent were mixed according to the ratio mentioned above. The mixture was then poured into a metal mold and cured for 24 h at room temperature. Dimension of the resin casts in tensile test is 90 mm (L) × 13 mm (W) × 7 mm (T), while in bending test is 60 mm (L) × 13 mm (W) × 3 mm (T). Calibrating length in both tests is 50 mm with cross-head speed of 2 mm/s. All the mechanical tests were accomplished on Zwick-Z010 servo-electric testing machine at room temperature. In the single fiber pull-out test, the cross-head speed is 1 mm/min. The load boundary condition is that load acted on one SMA end with epoxy host fixed. Five specimens were tested at each point of an experiment.
Mechanical properties of Carbon-matrix composites for a blade runner’s artificial leg
Published in Cogent Engineering, 2021
Rifky Ismail, Dewi Paras Utami, Mochamad Arid Irfai, J. Jamari, A.P. Bayuseno
In this present study, carbon fiber composite with fiber direction 0/90° was made on varying matrices of epoxy bakelite, resin casting, orthocryl, and polyester PMMA (Polymethyl methacrylate) matrices using the infusion resin method. Here, the most proper amount of resin to bring a blade runner’s artificial leg with carbon fiber composite was evaluated. Moreover, the designed composite with a variety of matrices was then examined by tensile, impact, bending, hardness testing, respectively, while density and porosity were examined. The study is expected to provide a practical insight into the effects of varying matrices on the mechanical properties of FRP composite for the blade runner’s artificial leg.