The objective of this work was to create a methodology to identify the location and magnitude of varying stiffness in paperboard. The Virtual Fields Methods (VFM) enforces equilibrium between internal work and external work, both on the entire test specimen and small segments of the test specimen to identify variations in paperboard stiffness both in simulations and actual tensile tests. Using a local equilibrium approach, segmented VFM and Fourier?VFM (F-VFM) gave more accurate identification of local stiffness than the homogeneous identification of global stiffness. The F?VFM formulation could identify a smoothly varying stiffness such that local equilibrium was improved from the homogeneous assumption, i.e. all locations in the material have the same stiffness, and the segmented VFM approach, where segments of the material could have different, distinct stiffness. This work provides a methodology to probe all heterogeneous materials but was applied here for heterogeneity in paperboard. The research assesses the capability of different VFM techniques. It is applicable to damage assessment and as part of an off?line process control system that can improve strength of machine-made paperboard and enable a basis weight reduction in paperboard used in corrugated containers with a net cost savings for the companies and reduction in need for pulpwood.