Self-healing microcapsules´ performances of friction noise in composite brake

Micro cracks are usually formed in composite components under librating or friction load. New method with technology of self-healing microcapsules is put forward in this paper. In the crack´s extending, the stress is concentrated at the crack end, where the microcapsule is designed to be located. When the stress goes through the microcapsules and causes them to break, the self-healing liquid runs out to fill the crack by the capillary and it will poly-react with catalyst in the composite. As a result, the crack is healed. Dicyclpentadiene (DCPD) microcapsules coated with poly (urea-formaldehyde) as self-healing capsules are chosen and their ingredients are prepared according to our past experiments and researches. The friction noise performances of the two groups are studied that the composite material of one brake sample is implanted by the self-healing microcapsules and the other sample has none. Testing experiments for friction noise at certain temperatures, such as 373K, 423K, 473K and 523K, are carried out in anechoic laboratory on XL 112 fixed-speed friction tester. Sensor INV 9205 is used for noise signal´s collection and contrastive analysis is made by special software. Investigations indicate that the frequency of friction noise for the two kinds of samples varies from 500 to 2000 Hz. The sound pressure levels for samples with microcapsules are generally 11.85 % lower than that without microcapsules at the same temperature and the same frequency. That is because the microcapsules play the role of pores and they can absorb noises in frictions. Therefore, the application of self-healing microcapsules in composite brake may extend the part´s lifespan and reduce the noises in friction.