Three-dimensional (3D) forming of fibre-based materials has been a topic of growing interest over recent years and 3D forming processes using hydroforming, press forming and deep drawing processes have been widely explored. Thermoforming as a potential alternative method for forming these materials remains, however, relatively understudied. This research attempts to provide a fundamental understanding of the thermoforming limitations of plastic-coated paperboards. In the work, a variety of commercial paperboards are subjected to experimental tests with different forming parameters and moulding depths. Shape accuracy, maximum acquired depth, thickness distribution behaviour and damage mechanisms are used to evaluate thermoformability, and the results linked to the material properties and forming conditions. The research findings indicate that the plastic-coated paperboards studied are thermoformable but only in simple geometric shapes and with low mould depths.Unlike plastic, thermoforming can result in thickness increase in plastic-coated paperboards, which is thought to be a result of out-of-plane auxetic behaviour of paperboards. Paperboard thermoforming was also found to be hindered by rupture, blistering and curling defects. Tensile strain at break is the key factor determining thermoformability. Additionally, the density of the paperboard can impact the heating step and the rate at which the moisture content of the material changes during the forming process. Furthermore, it was observed that changes in process parameters affected materials differently, with the direction and rate of change differing based on the material being used.

Advances in the three‐dimensional (3D) forming of fibre‐based materials require the formulation of more formable materials and the development of process lines, machinery, and tools. Using a thermoforming process to convert fibre‐based materials into 3D forms is an emerging area of research which requires further investigation into the practicality of the process line and tooling in forming such materials. Accordingly, this study evaluated the impact of the thermoforming process operation and tooling on the thermoformability of plastic‐coated paperboards. The main objective was to provide design recommendations for the future development of thermoforming lines, followed by guidelines for tooling design to improve the performance of materials utilising the currently available machinery. This study examined the thermoforming behaviour of two different plastic‐coated paperboards in vacuum and pressure thermoforming by investigating their maximum acquired depth, shape accuracy, and damage mechanisms. The research findings, based on the depth and linear elongation achieved, indicate that the inferior performance of plastic‐coated paperboards in thermoforming cannot be wholly attributed to restrictions in the three‐dimensional formability of materials; the inability of the current process lines to utilise the maximum potential of materials can also lead to their inferior performance. Notably, the method of pressure supply and cooling of materials requires adjustment of these materials. From a tooling perspective, owing to the spring‐back effects, the enlargement of the mould dimensions should be considered during the design stage. Additionally, based on potential opportunities with the current unmodified machinery and materials, products in the size of standard food trays have a higher likelihood of being optimised with tooling design than smaller sized shapes, which still require additional developments in materials. Moreover, designing moulds without draft angles can reduce the risk of rupture owing to the prevention of localised stress formation in materials.

The large volume of industrial by-products and wastes from the construction, timber and paper industries has become a serious challenge worldwide. Recycling these industrial wastes as functional materials in the construction industry is an efficient approach for sustainable development. This study presents a pretreatment approach for recycling construction and demolition waste (CDW) and industrial side-streams (such as green liquor sludge, fiber waste, flotation sand and fly ash) in order to produce a geopolymer for the 3D printing of construction materials. A treatment approach was developed for screening the residues from CDW with a maximum size of 16 mm and for a combined line treatment for industrial side streams. The treatment processes utilized suitable and economical separation techniques for the recycling of waste materials. The crushing of the screened residues resulted in a homogeneous material size that facilitates the separation of mixed wastes and simplifies the classification of materials. The combined plant enabled the cost-effective treatment of various industrial wastes in a single process unit. The results show that the economic and environmental impact of the chosen techniques, in terms of their energy consumption, is highly dependent on the treatment line, separation technique and quantity of the individual waste that is processed. These recycled industrial wastes can be used as sustainable materials for the production of geopolymer concrete, contributing to the sustainability of the construction industry.