Modulus of rupture specimens were used to determine crack growth parameters of a porous mullite material. Strength testing was performed in ambient and moist environments. The power law crack growth rate parameters n and 1n B in 50 percent relative humidity were found to be 44.98 and 0.94, respectively. The inert strength, fracture toughness, and elastic modulus were also determined and found to be 19 MPa, 055 MPa(m) exp 1/2, and 11.6 GPa, respectively. Viens, Michael J. Goddard Space Flight Center ...