To Örebro University

Carton board packages subjected to concentrated loads near the edges are damaged in a characteristic way. This paper reports an attempt to simulate the damage process in the lab and Package Collapse Loads measured for this load case.

Packages were compressed by a concentrated load. The position of load application was varied along a line parallel to a crease and the package was rotated in order to test the influence of the height of the load carrying panel. Force and displacement were recorded and the damage evolution during the test was studied. The damage produced was examined using x-ray tomography. The nature of damage at different stages of damage evolution was studied.

Both the visual appearance of the damage and the force-displacement curve were similar in all tests. The Package Collapse Load has little dependence on where along a line parallel to a crease of the package the point load is applied. Damage started developing at the crease and a yield line perpendicular to the crease and parallel to the direction of the load developed. When the displacement increased further, a parabolic yield line, symmetric around the previous one, developed. The start of the damage development was associated with at peak in the force-displacement curve. Stiffness was more geometry dependent than strength. On macro scale, the visual appearance of the damage due to concentrated loads shows no significant dependence on geometry.

Consumer packaging made from carton board is subjected to a variety of loads as it moves through the value chain. Packaging designers need tools for predicting the strength of packages under these loading conditions. For evenly distributed loads, there are methods for measuring and estimating compression resistance that can provide useful guidance. For loads concentrated to a small area, little work has been published. The aim of this preliminary study is to aid the development of a future test method for point loads by investigating how the size of the load application site influences the mechanical behaviour of the package. Rigid spheres of a range of sizes were used to compress packages. Small spheres gave rise primary damage in the form of a vertical yield line and secondary damage in the form of a parabolic yield line. Larger spheres produced a series of parabolic yield lines of increasing size. No vertical yield line appeared for the larger spheres. The larger spheres showed a stiffness transition at a displacement that could be estimated by considering the geometry of the test.

This work reports the evaluation of a tactile sensor for the potential of using it to measure the compliance of folding cartons. A tactile sensor would make it possible to measure the mechanical behavior locally around the contact point, in contrast to existing methods that measure the global mechanical behavior of the carton. Research on the haptic sense has shown that the local mechanical behavior is more important than the global behavior when humans assess compliance of objects. It is shown that the response of the tactile sensor correlates strongly with the bending stiffness of the board, but also with geometric features. A method for reducing the 22-dimensional output of the sensor to single meaningful feature using linear discriminant analysis is proposed and tested. The results show that the sensor is a good candidate for a method that incorporates both cutaneous and kinaesthetic information in the measure of carton compliance.

The importance of sensory information in product purchasing decisions has gained increasing attention in recent years. Tactile properties of packaging are usually measured with the help of trained evaluators. An objective, fast and repeatable method that describes the mechanical interaction and does not rely on a panel would have many benefits. We propose and evaluate such a method for measuring the mechanical interaction between a deformable finger-like shaped sensor and a package. Evaluation of the method shows good repeatability, the variability in the measurement result is within a few percent in most cases. The method captures indentation differences at contact between sensor and package due to measurement position and package design.