Transverse Cracks


 -- -7t --- -4~
 Delamination Debonding of the facesheet

Figure 1-3. Damage progression at cryogenic conditions.

 The damage progression of laminated composites at cryogenic temperatures is

illustrated in Figure 1-3. At cryogenic temperatures, the microcracks initiate and

propagate in laminated composites due to difference in thermal contraction between the

fiber and matrix phases. When microcracks in the polymer matrix develop and reach the

adjacent layers, the transverse cracks initiate. When the transverse crack develops further,

the crack deflects through the interface between layers and delamination initiates. In the

case of composite sandwich construction, debonding of the facesheet develops.

 The purpose of this study is to investigate the possible causes of failure in

laminated composites at cryogenic conditions. First, the micromechanics method is

developed to predict the thermal stresses at microscale in fiber reinforced composites at

cryogenic conditions. Second, fracture toughness of a transverse crack in composite

laminates is evaluated to investigate the effect of cryogenic conditions on transverse


Microcracks