EFFECT OF LAMINATE DESIGN AND LOADS ON CRACK OPENING VOLUME IN LAMINATES USED IN CRYOGENIC TANKS

The use of advanced composite materials for cryogenic fuel tanks reduces the mass of the structure but the leakage of fuel can become a problem. Since the amount of leakage will increase with crack opening volume, it is essential that we understand the factors that affect the crack opening. In a previous study by the authors, the degradation behavior of lamina properties due to cracking was studied extensively. The study examined the effects of a variety of parameters such as adjacent ply orientation, material properties of adjacent plies, initial properties of the cracked ply, and cracks in adjacent plies on the effective properties of the cracked ply. It was shown that the rate of degradation is not very sensitive to these parameters. In the current paper, it will be shown that the crack opening volume can be directly related to changes in effective moduli. A simple calculation of the crack opening volume for a laminate based on the degradation of the E22 of a cracked lamina is presented. The effect of various parameters on the crack opening volume shows a similar pattern as the E22 degradation of a cracked ply. This suggests that the opening volume is expected to also be quite insensitive to the laminate design parameters listed above.