Hot Isostatic Pressing Process｜Fabrication of Ceramic Matrix Composites｜ ENGINEERING STUDY MATERIALS)

Hello viewers, welcome to engineering study materials. Today we are going to discuss about the hot pressing process for the processing of ceramic matrix composites. So let's get into this video. Hot pressing is a simultaneous application of pressure and high temperature. So this can accelerate the rate of densification and a pore free fine grain compound can be obtained. It involves two stages, incorporation of a reinforcing phase into an unconsolidated matrix and matrix consolidation by hot pressing. It is also called as slurry infiltration process. This diagram shows the complete process of the hot pressing. First the spool consisting of a reinforcement in the form of a filament or a wire is taken. Then it is followed to a container which contains slurry that is powdered glass in water and resin binder. Then it goes forward to the take-up drum from which it can be obtained in form of a plate or a sheet. Then it can be cutted into pieces. Then it can be stacked together. Then it can burn out in a furnace for the sintering or the consolidation process. Finally the load is applied heat and pressed in a hydraulic press so that the densification is obtained. By this we can easily produce the composite products. A fiber tow or a fiber preform is impregnated with a matrix containing slurry by passing it to a slurry tank. This slurry consists of the matrix powder, a carrier liquid and an organic binder. Then this organic binders burned out prior to consolidation. Wetting agents may be added to ease the infiltration of the fiber tow or preform. This impregnated tow or a prepreg is wound on a drum and dried. This is followed by cutting and stacking of the prepregs and consolidation in a hot press. This prepregs can be arranged in a variety of stacking sequences. The stacking process is an important process in this type of composite production because the stacking involves the, it can enhance the properties of the composite product. If the sheet is stacked in only in one direction such as the zero degree, the strength is only supposed to have in the only one direction. It is not in the other direction that is y direction. If you have placed the stacks, stack of piles or composites in both the zero degree, 90 degree, 45 degree means we can get the multidirectional property and have good strength in all the directions. Then the slurry infiltration process is well suited for glass or ceramic matrix composites mainly because the processing temperature of these materials are lower than those used for crystalline matrix materials. Any hot pressing process has certain limitations also because of the complex shapes. So here are the process parameters. These have to be managed suitably. That is precise control with a narrow working temperature range and minimization of the processing time, utilization of the pressure low enough to avoid fiber damage. Here also the fiber damage is the critical part for the composite production because if the fiber is lengthy and strong, the final composite product is also in good strength property. If it is damaged, the complete product is get wasted or the property losses in the composite product. Then this is the hot pressing graph. Temperature is increased to 600 to 700 degree Celsius and further increase with the addition of the pressure. It is maintained stable and then it is lowered so that we can get these grains. So the advantages are low porosity products can be obtained easily and high strength and toughness can be obtained. The disadvantages are relatively low melting or softening point of the matrix material because we use the glass as a reinforcement. The glass melts between 600 to 700 degree Celsius or even lower that so that the final product also melts at low melting point. So this is a short video friends. If you like this video, please click the thumbs up button and share this video to your friends to gain knowledge and don't forget to subscribe this channel for more videos. So thank you for watching.