The results of the maximum principal stresses in the fiber and matrix phases in

each layer of the laminate are shown in Tables 2-13 and 2.14. When the cryogenic

temperature is applied to the composite tank without tank pressure, the maximum

principal stress in the matrix phase (70 MPa) is below its strength (100MPa). The result

indicates micro-stress in the matrix phases, although very high, is not enough to initiate

microcracks. However, when the tank pressure increases and reaches 10KPa, micro-stress

in the matrix in the inner facesheet exceeds the tensile strength indicating the possibility

of micro-crack development.