Accurate interlaminar stress recovery from finite element analysis
Abstract
The accuracy and robustness of a twodimensional smoothing methodology is examined for the problem of recovering accurate interlaminar shear stress distributions in laminated composite and sandwich plates. The smoothing methodology is based on a variational formulation which combines discrete leastsquares and penaltyconstraint functionals in a single variational form. The smoothing analysis utilizes optimal strains computed at discrete locations in a finite element analysis. These discrete strain data are smoothed with a smoothing element discretization, producing superior accuracy strains and their first gradients. The approach enables the resulting smooth strain field to be practically C1continuous throughout the domain of smoothing, exhibiting superconvergent properties of the smoothed quantity. The continuous strain gradients are also obtained directly from the solution. The recovered strain gradients are subsequently employed in the integration o equilibrium equations to obtain accurate interlaminar shear stresses. The problem is a simplysupported rectangular plate under a doubly sinusoidal load. The problem has an exact analytic solution which serves as a measure of goodness of the recovered interlaminar shear stresses. The method has the versatility of being applicable to the analysis of rather general and complex structures built of distinct components and materials, such as found in aircraft design. For these types of structures, the smoothing is achieved with 'patches', each patch covering the domain in which the smoothed quantity is physically continuous.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 September 1994
 Bibcode:
 1994STIN...9511815T
 Keywords:

 Finite Element Method;
 Interlaminar Stress;
 Laminates;
 Rectangular Plates;
 Robustness (Mathematics);
 Shear Stress;
 Stress Distribution;
 Aircraft Design;
 Analysis (Mathematics);
 Composite Structures;
 Equilibrium Equations;
 Loads (Forces);
 Smoothing;
 Structural Mechanics