INFLUENCE OF SHEET DIMENSIONS ON CURL OF PAPER

Out-of-plane hygroinstability (curl) of cross-plied square paper sheet s made from bleached chemical pulp has been studied analytically and e xperimentally. Theoretically, it is shown that nonlinear kinematics an d bifurcation response must be accounted for in the analysis of curl i n paper. Furthermore, a dimensionless formulation of the governing pla te equations for the curl curvatures revealed that a single dimensionl ess loading parameter controls the curl characteristics. Cross-ply she ets of various dimensions were manufactured from bleached chemical pul p to experimentally examine the curvatures and verify analytical resul ts. Measured changes in curvatures were compared with predictions from linear and nonlinear laminate theory and nonlinear finite element ana lysis. Good overall agreement was observed between analytical and nume rical results and between measured and calculated curvature changes.