Three Dimensional Thermal Stresses in Angle-Ply Composite Laminates

Abstract

Three-dimensional linear finite element analysis is used to compute the room tempera ture stress distributions and shapes of angle ply graphite/epoxy laminates of the form [+θ _n/-θ _n] _S with values of θ ranging from 15 ° to 75° . Analyses were performed with pro per boundary conditions and with improperly assumed symmetry conditions. Results in dicate that angle ply laminates with "clustered" plies will exhibit a tendency to delaminate at diagonally opposite corners. Earlier work by the author predicted the initiation of trans verse matrix cracks at the free edge in cross-ply laminates of the form [0 _n/90 _n] _S. In angle- ply laminates of the form [+θ _n/-θ _n] _S, however, the results indicate that matrix cracks will be initiated in the interior of the laminate, resulting in potential difficulties for ex perimental efforts using optical methods to detect cracking.