What is the Goal of Your Research?

Fig. 1 Microscope Photograph of CFRP Cross-Section


Fig. 2 CFRP Prepared in Laboratory


Fig. 3 Use of Round Fiber Can Efficiently Reinforce Periphery of Hole

What are current passenger aircrafts made of? The material for the body of aircrafts used to be aluminum alloy, but in many cases now, it is fiber-reinforced composite material or carbon fiber reinforced with resin.

For example, most of the surface structures on the Boeing 787 are made of carbon fiber-reinforced plastic (or the acronym CFRP) as shown in Figs. 1 and 2. The reason for this is that CFRP has physical properties that make it lighter and more durable than metallic materials. The characteristics of being “lighter” are very important for machines in general when the objective is to move. Because the lighter weight of mechanical structures can “increase fuel efficiency.” Trimming the weight of the newest passenger aircraft Boeing 787 improved the fuel consumption as well as the flight distance. Now, CFRP is utilized for not only aircrafts but also various products such as space rockets, automobiles, tennis rackets and portable PCs, taking advantage of the lighter and durable characteristics.

Our laboratory intends to contribute to the higher performance and function of mechanical structures by researching and developing efficient designs and using CFRP for its beneficial characteristics as mentioned above. For example, in the natural world, you can find many fiber-reinforced plastics made by nature such as the leaf veins in plants and the collagen fibers in animal bones, which are not straight but curved in shape. Investigating the structures from the standpoint of structural mechanics reveals that the shape and distribution of these fibers is excellent for bearing external forces. By emulating these natural materials, creating the best shape using curved CFRP fibers (only straight fibers were used before) may result in the design of new mechanical structures with higher performance. This idea led us to develop a numerical calculation method and optimizing algorithm (Fig. 3) in order to achieve CFRP structure optimization using round-shaped reinforced fibers. And now, we are verifying these structures through experiments.

 

What Kinds of Devices are You Using in Your Experiments?

Fig. 4 Graduate Students Teaching the Method of Vibration Experiment to Short-Term Foreign Students

Have you ever been turned off or felt uncomfortable by the wobbly or bumpy movement in automobiles or trains? The vibration in machines is troublesome because it not only annoys passengers but also lowers driving safety or damages materials. An elegant design of structures to suppress such vibrations or to avoid a large swinging caused by resonance is one of the important research subjects in mechanical engineering. Our laboratory creates CFRP which is optimized and designed using numerical simulations, and we conduct experiments to verify whether it follows the expected vibration performance and strength.

For numerical simulations, many original calculation programs have been developed to make calculations, which cannot be achieved using general-purpose calculation programs. In addition, we create CFRP and measure vibrations at our experimental laboratory. In our experiments, we use vibration measurement devices employing small acceleration sensors and the Doppler effects of laser light, devices to amplify electrical signals or eliminate extra noise, systems to collect data at extremely high speeds and other devices.

 

What Will be Your Next Goal?

Fig. 5 Smart Composite Material that Instantly Suppresses Vibration, and Vibration Experimental Result

I would like to develop a smart composite material to improve the performance of fiber-reinforced composite materials, which include but are not limited to CFRP. The smart composite material is a composite equipped with a mechanism which detects vibrations and instantly suppresses the vibration. Fig. 5 shows a smart composite material which combines CFRP and “piezoelectric material” which contracts and expands depending on the electric voltage.

Going forward, I would like to develop controlling programs that employ artificial intelligence which can spontaneously learn “How much regulating force can effectively suppress the vibration under specific conditions?” and apply this to the structure shown in Fig. 5