Consider the structural situation as given in Fig. 1. The employed
nomenclature for the geometric properties of the specimen is
explained in Fig. 2. Herein, l1; b1 and h1 are the length, width and
height of the plate, while l2; b2 and h2 are the geometric properties
of the doubler. Apparently, this structural situation exhibits certain
symmetry properties that will be taken advantage of in the following.
Both the plate and the doubler are manufactured of symmetric
cross-ply laminates so that none of the typical coupling effects (i.e.
extension–shear-coupling, extension–bending-coupling, bending–
twisting-coupling) occur due to the employed lamination schemes.
However, as will be shown later on, due to the discontinuity of the
height of the structure, some secondary bending effects will occur
nevertheless, even though the structure is subjected to a plane tensile
load.