Stress Analysis and Strength Characterization of Thick Composite Laminates

This final report covers the theoretical development of and experimental results for the stress analysis and strength characterization of thick composite laminates. Thick composite laminates (consisting of 38 plies or more) are being evaluated for use in future high performance anti-ballistic missiles and other aerospace applications. The theoretical development includes the derivation of a high-order theory of plate deformation which accounts for the affects of transverse shear deformation, transverse normal strain, and a non-linear distribution of the in-plane displacements with respect to the thickness coordinates. The theory is developed for both homogeneous and laminated plates. Further examination of this high-order plate theory via stress solutions which have been carried out to assess its accuracy. This theory, in effect, enables close estimation of three-dimensional stress components from essentially two-dimensional analysis. The effects of the three-dimensional state of stress on the strength of a thick laminates are analysed with a 3-D failure criterion. The tensor polynomial method is extended with full account given to three-dimensional stress state effects and is presented together with experiment and evaluation of the coefficients.