Design of Iosipescu shear test for applying to a bi-modulus ceramic-fiber-reinforced SiO₂ aerogel

Tension and compression tests were conducted on a ceramic-fiber-reinforced SiO2 aerogel (CFRSA). The material exhibits different tension and compression modulus, i.e., bi-modulus. The objective of present research is to establish guidelines for preparing shear tests of this CFRSA. Finite-element analysis (FEA) on various Iosipescu specimens is presented for four bi-modulus materials, including the CFRSA. It is found that the major concerns for specimen design of bi-modulus materials are: the uniformity of shear stress and the longitudinal normal stress concentration at notch tips. These concerns are all dependent on material properties. For material with Et numerically close to Ec, the normal stress concentration near notch tips is of less significance. However, for material with high tension-compression asymmetry, including this CFRSA, the normal stress concentration near notch tips is significant. The round-notch specimen with small normal stress concentration seems to be favorable for these materials.