学术报告——Carbon-fiber aluminum-foam sandwich with short aramid-fiber interfacial toughening

     Interfacial toughness and toughening mechanisms of a sandwich beam, consisting of an aluminum foam core covered with two carbon-fiber/epoxy composite face sheets, are investigated in this study. Short aramid fibers of different lengths and densities have been inserted at the interface during the sandwich fabrication process, to improve the interfacial toughness of the sandwich beam.

The results indicate that the average critical energy release rate G_Cof the carbon-fiber aluminum-foam sandwich samples with the aramid fibers increases by about 100%than the non-toughened samples. Improvements of varying degrees in the interfacial toughness were observed for all specimens toughened with short aramid fibers of different lengths.

The interfacial toughening performance and underlying mechanisms for energy absorption were discussed and analyzed using scanning electron microscopy. For the sandwich samples fabricated in this study, short aramid fiber, are more effective than longer aramid fibersas free aramid fiber ends from those short aramid fibers can more effectively utilize surface cavities of the rough-surface aluminum foam, thus leading to more effective fiber-bridging and higher interfacial toughness.

    This study aims at developing a process technique, which can deposit porous scaffold-like hydroxyapatite (HA) coatings on strong ceramic substrates. As a first trial, micro-porous HA coatings on strong zirconia-based substrates are fabricated by the following technique—consisting of low-density HA-slip coating-deposition on the micro-porous substrates pre-sintered at 900◦C, and coating-substrate co-sintering at 1300◦C. The final co-sintering process ensures a strong bonding between the HA coating and the zirconia-based substrate after minimizing the mismatch in thermal expansion coefficients by adding alumina in HA coating and HA in zirconia-based substrate. The presence of porosity in the HA coating also reduces the mismatch. HA decomposition during the co-sintering process is discussed.