Advanced calculation of the room-temperature shapes of unsymmetric laminates

It is well known that the room-temperature shapes of unsymmetric laminates do not always conform to the predictions of classical lamination theory. Instead of being saddle shaped, as classical lamination theory predicts, the room-temperature shapes of unsymmetrically laminated composites are often cylindrical in nature. In addition, a second cylindrical shape can sometimes be obtained from the first by a simple snap-through action. Since 1981 several models, which are restricted to rectangular plates and sometimes only some special lay-ups, have been developed. The Finite Element Analysis (FEA) has just recently been used for the calculation of the room-temperature shapes of unsymmetric laminates, because more sophisticated finite element codes are now available and the calculations can be made in an acceptable time. Using the FEA there are no restrictions concerning the laminate geometry or the lay-up and the snap-through effect can be modeled. Additionally the edge-effects can also be monitored in the FEA results. Unsymmetric laminates can become important for aircraft applications especially for the aeroelastic tailoring.