In this lecture prof. C. Kassapoglou talks about what happens when you add a stiffener to a composite plate.

He starts with a continuation on the effective width derived in the previous lecture, comparing it to finite element results. He continues by talking about how to deal with boundary conditions for stiffeners in a structure.

The second segment of the lecture covers composite stiffeners, starting with a general description of different types of stiffeners used and their properties. A guideline is given for layups of composite stiffeners which is then applied to an example to point out problems that have significant impact on the design.

Prof. C. Kassapoglou then talks about obtaining the equivalent properties for a composite stiffener by looking at each part of the stiffener individually. He then concludes the lecture with a detailed discussion on column buckling for beams supported by an elastic foundation using Castigliano’s energy minimization method.