Scaling of first-ply failure and strength in [+theta(n)/-theta(n)/90(2n)](s) laminates: Experiments and predictions

An experimental investigation of first-ply failure and strength was conduct ed on ply-level scaled carbon/epoxy composite laminates having a stacking s equence of [+theta(n)/-theta(n)/90(2n)](s) where the constraint ply angle, theta, was varied from 0 to 75 degrees, and it varied from 1 to 4. First-pl y failure was shown to depend on the level of constraint and the scale fact or, n. The strain energy release rate for matrix microcracking was computed from first-ply failure data of the [0(2)/90(2)](s) laminate, Then, first-p ly failure for all other layups was predicted using a numerical model that accounted fur both constraint and size. Tensile strength was predicted usin g a strain energy release rate model for delamination of surface angle plie s. A delamination energy value for each ply angle was calculated from the t hinnest (n = 1) laminates to predict strength of the other sizes.