A segment is a straight line joining 2 nodes in the drawing that represents the cross section of the beam as shown in Figure 10.1.

From the material’s point of view, each segment represents a panel, also called webs and flanges. Each panel is composed of a number of laminates, each having a number of laminas. All the properties of those laminates put together into a panel are summarized by the Segment Stiffnesses, as follows:

*Ai*is the membrane axial stiffness of the panel/segment along the length*x*of the beam.*Di*is the bending stiffness of the segment.*Bi*is the bending-extension coupling of the segment that appears when the panel in not symmetric through its thickness.*Fi*is the inplane shear stiffness of the segment.*Hi*is the twisting stiffness of the segment when subjected to shear flow*q*. This is better explained in the textbook.*Ci*is the twisting-shear coupling of the segment.

Segment stiffnesses are to panels what *A, B, D, H* matrices are to laminates. Laminates are analyzed in chapter Macromechanics.