Volume 23, Issue 4 (July 1995)
Stiffening Effects of Photoelastic Coatings on Orthotropic Plates
Photoelastic coatings have been used successfully for years to help engineers understand the stress state within a test specimen or structural component under load. For very stiff specimens, the addition of a photoelastic coating does little to change the stress state within the specimens. However, photoelastic coatings used with relatively flexible specimens have a significant stiffening effect which has been quantified and documented for isotropic materials. Correction factors have been developed that allow the analyst to account for the stiffness added to the specimen by the coating. This technical note addresses the stiffening effect of isotropic photoelastic coatings on orthotropic specimens, and provides orthotropic correction factors needed to correctly interpret stress results obtained using photoelastic analyses. The derivation of these correction factors assumes that loads are applied only along principal planes. Consequently, shear stresses due to specimen orthotropy are not present.