Different numerical techniques for the estimation of multiaxial stresses in symmetric/unsymmetric composite and sandwich beams with refined theories

A set of simple but efficient and accurate higher-order displacement models are used to evaluate the multiaxial stress behavior in symmetric and unsymmetric composite and sandwich laminates. These theories incorporate a more realistic non-linear variation of displacements through the beam thickness, thus eliminating the use of shear correction coefficient(s). Constitutive relations are used to evaluate inplane stresses. The computer program developed incorporates the realistic prediction of transverse stresses from equilibrium equations. The integration of the equilibrium equations is attempted through direct integration method, forward and central direct finite difference technique and a new approach called an exact curve fitting method. The versatility of the present higher-order theories is demonstrated by comparing the results with the available elasticity and other closed-form solutions for cross-ply and sandwich laminates. The results show that the exact curve fitting method gives good estimates of multiaxial stresses compared to finite difference and direct integration methods