A simple, one-dimensional model for perfectly plastic hinges, utilizing a hinge yield strength, was applied to wrinkled paperboard and validated. The hinge model was incorporated into a three-dimensional constitutive model of paperboard including wrinkle initiation, wrinkle compression, as well as tensile reloading of wrinkled paperboard. The constitutive model enables the explicit finite element simulation of the deep drawing of a non-creased paperboard blank, including spring-back after the forming process. The results of the simulated deep-drawing process were validated against experimental deep-drawn paperboard cups, and parametric studies were conducted to investigate the effects of process and material parameters on three different quality measures (spring-back magnitude, asymmetry, and punch force). In addition to aiding the development of the simulation of paperboard deep drawing, the hinge yield strength was also found to be the only studied material property which could simultaneously improve all three quality measures.

Cellulose partially converted to dialcohol cellulose has been identified as a potential breakthrough material for the production of bio-based, complex, double-curved surfaces due to its extensive strain-at-break characteristics (reaching as great as 80% in tensile loading). Tensile testing of handsheets made from modified cellulose fibers was conducted from 50 to 90% relative humidity (RH) and from 23 to 150 °C. Strain-at-break of the handsheets ranged from 35 to 80% over this humidity and temperature range, which is significantly greater than typical cellulose-based materials. The combined effect of moisture and temperature was further investigated by dynamic mechanical thermal analysis, which was utilized to determine the glass-transition temperature of the handsheets as a function of relative humidity. Based on the tensile test results and verified by the three-dimensional (3-D) forming and simulation, a forming limit diagram (strain-based failure surface which describes and illustrates the formability of the material) for the handsheets was generated. This forming limit illustrates significant extent to which this bio-based material can be 3-D formed into advanced structures. Furthermore, temperature was identified as the best, quickest, and most controllable method of improving extensibility of this material during 3-D forming.

This data article contains the dynamic mechanical thermal analysis (DMTA) results for sheets made from cellulose fibers partially converted to dialcohol cellulose as presented in “Advanced Three-Dimensional Paper Structures: Mechanical Characterization and Forming of Sheets Made from Modified Cellulose Fibers” by Linvill et al. [1]. See Larsson and Wågberg [2] for a description and characterization of the material as well as how the material is produced. The DMTA tests were conducted at four different relative humidity levels: 0, 50, 60, and 70% RH, and the temperature was swept between 10 and 113 °C. The DMTA results enable the understanding of the elastic, viscoelastic, and viscoplastic mechanical properties of this material at a wide range of temperature and relative humidity combinations.

This data article contains the dynamic mechanical thermal analysis (DMTA) results for sheets made from cellulose fibers partially converted to dialcohol cellulose. See Larsson and Wågberg [1] for a description and characterization of the material as well as how the material is produced. See also Linvill et al. [2] for tensile testing and 3-D forming of the material. The DMTA tests were conducted at four different relative humidity levels: 0, 50, 60, and 70 % RH, and the temperature was swept between 10 and 113 °C. The DMTA results enable the understanding of the elastic, viscoelastic, and viscoplastic mechanical properties of this material at a wide range of temperature and relative humidity combinations.

Understanding the biaxial (in-plane) failure behavior of paperboard is crucial to understand the limits of 3-D forming of paper materials, because the biaxial strain failure limit determines the extent to which paperboard can be formed in different conditions.

A traditional cruciform biaxial specimen has been redesigned and modified with the help of laser engraving. By the use of laser engraving, 90 % of the effective thickness of the specimen in the center of the cruciform was removed, thus making the cruciform specimen more likely to fail in the center than at the edges. A variety of strain ratios were utilized to test the specimens with a biaxial testing machine, and the strain field was measured utilizing digital image correlation.

The results of the biaxial testing were analyzed in order to determine both the strain-based yield and failure surfaces. Additionally, the stresses in the center of the specimen were estimated based on the forces measured during the test. Based on these estimated stresses, stress-based yield and failure surfaces were also constructed. Furthermore, various models for the strain- and stress-based yield surfaces were applied to the data and compared.

Paperboard is oftentimes subjected to biaxial in-plane stress and strain states, although very few experimental studies of the biaxial in-plane yield and failure of paperboard have been conducted. A new biaxial testing method to determine the in-plane stress- and strain-based yield and failure surface of paperboard was proposed and implemented. The method utilized cruciform specimens containing a reduced-thickness region (prepared by laser engraver) to increase probability of failure in that region, and digital image correlation was utilized to measure strain. The obtained stress-based failure surface was similar to previously reported results in the literature, but the obtained strain-based failure surface differed from the one previously reported strain-based failure surface. The obtained yield and failure surfaces had similar shape, providing confidence in both results due to the related deformation and failure mechanisms in paperboard. Furthermore, the overall shape of the stress- and strain-based yield surfaces was unaffected by the definition of the yield point. The obtained strain-based failure surface revealed the forming limits and therefore strengths and limitations of various 3-D forming methods for paperboard.

Deep drawing of paperboard requires the creation of wrinkles for successful forming of a paperboard cup. A phenomenological model for the mechanical response of wrinkles is proposed and based on the assumption that the wrinkles have a mechanical response equivalent to that of a plastic hinge (i.e. the internal moment in the hinge is held constant during deformation). This 1-D model has been verified with two experiments.

            Furthermore, this phenomenological model has been expanded into a 3-D continuum constitutive model, which considers the initiation and propagation of wrinkles, large deformations due to wrinkle formation and wrinkle compression, and permanent deformations. This 3-D continuum model has been compared to and verified against experimental deep-drawing results. Experiments and simulations have been compared in terms of springback, wrinkle propagation, and punch force. Additionally, the model provided insight into the deep-drawing process by establishing better understanding of the initiation of wrinkling.