A comparative study for the calculation of the temperature dependent shapes of unsymmetric laminates based on finite element analysis and extended classical lamination theory

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. Hyer examined the class of all square unsymmetric cross-ply laminates which can be fabricated from four layers, i.e., [0/0/0/90], [0/0/90/0], [0/90/0/90], [0/0/90/90], and developed an extended classical lamination theory to predict whether these laminates have a saddle shape or one or two cylindrical shapes. 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. The hope is to get more accurate results for the shape and the stresses and forces that occur during the snap-through action. These results are needed for the development of active deformable composite structures based on unsymmetric laminates and incorporated shape memory alloy wires [1]. Results for different lay-ups are presented and compared.Published in Mekhanika Kompozitnykh Materialov, Vol. 31, No. 3, pp. 341–350, May–June, 1995.