Compressive properties and fracture behavior of ceramic fiber-reinforced carbon aerogel under quasi-static and dynamic loading

The quasi-static and dynamic compressive properties of a ceramic fiber-reinforced carbon (CFRC) aerogel were investigated using a universal test machine and a split Hopkinson pressure bar. The fracture surface of the CFRC aerogel was studied by scanning electron microscopy. Results show that the compressive behavior of CFRC aerogel exhibits a significant strain rate strengthening effect. The quasi-static failure strain is higher than the dynamic failure strain. Under quasi-static compressive loading, the carbon aerogel matrix breaks into small pieces at a strain of 0.75 and fibers separate from the matrix. The deformation of the fibers is not obvious, indicating that fibers suffer little stress. Under dynamic compressive loading, the aerogel matrix shatters into fragments at a strain of 0.62 and shows a "bursting" phenomenon. The high speed compression of gas in the aerogel results in an increase of the internal stress. Fibers bend, break and separate from the matrix, indicating that fibers carry partially the applied loading. The carbon nanoparticles are squeezed closer with nearly no voids remaining after both quasi-static and dynamic compression. The increase of the internal stress and the fracture of fibers lead to strain rate strengthening and earlier fracture of the CFRC aerogel at high strain rates.