A bonded polariscope for three-dimensional photoviscoelastic studies

Abstract

A method of incorporating an internally bonded polariscope into a transparent model has been developed for use with viscoelastic materials. The newly developed technique serves to isolate one or more planes in a three-dimensional model so that a threedimensional photoviscoelastic analysis can be performed. The model may be subjected to a variety of loadings at room temperature, and only the photomechanical effects in the isolated plane will be observable.

In the experimental program, a viscoelastic cement was developed whose mechanical properties matched those of a chosen model material. The cement was used to bond the polarizing sheet into the model. The restraining effect of the stiff elastic Polaroid sheet was reduced by cutting a gridwork of slits into this material. Tests performed on simple disk models and on star-grain rocket models containing bonded-polariscope elements showed structural continuity through the cemented joint. The fringe pattern observed through the bonded polariscope in star-grain models was the same as that observed using a conventional polariscope. On the basis of the favorable test results, the newly developed technique was judged acceptable.