This research investigates the challenges a user faces in the activation step in shape-changing products. First, previous research on the topic of 4DP is reviewed and important factors are described. Namely, activation temperature, print temperature, print speed, and layer height have a signifi cant impact on the shrinkage of SMPs, during the activation step in 4DP. These shrinkages can be applied to an object through the use of varying strategies. These strategies show there are two ways of applying SMPs to a design, either calculate the shrinkage or create limits with the use of geometry-based end stops. Lastly, a further review is conducted into the type of products made with 4DP. These products turn out to be made out of three categories; fl at-packed, custom fi tment, and energy-absorbing structures.  The second chapter, Material Tinkering & Exploration, delves into the material characteristics of LW-PLA, showcasing its utility for shapechanging. LW-PLA can be used both as a passive and active element, reducing environmental impact by enabling or disabling shape memory through micro-scale structural changes. This material is then used to fi nd a correlation in curvature and ratio of active versus passive elements within a design. Furthermore, the material is used to fi nd the best type of heat source, trying to create the most consistent outcomes. The oven without convection is then chosen as it creates the most consistent outcomes by limiting user interaction and making use of slower response times.  The following chapter brainstorms ideas that can make use of shape change. Through the use of criteria and Edison profi les a direction is chosen. This is the direction of the temples of glasses. Shape change can add to this product as the temples vary in length to fi t different users. This chapter also creates two prototypes to be tested, differing in the type of measurement method.  Lastly, the design is evaluated through the use of two user studies. In the fi rst study, the focus is laid on the type of measuring method. The external measurement method comes out as the most promising as it creates the most consistent outcome with the users. The second test tries to minimize the error between the targetted length of the temple and the actual length after the activation process has ended. The result is an addition of two test samples that educate the user. Through the education of the user, a consistent result with minimal error can be achieved. The activation step also requires a homogeneous method of heating the temple, small deviations in this heating lead to unwanted curvature. This is combatted by creating a tray, that is delivered together with the temple.

This thesis investigates novel foaming materials for fused deposition modelling (FDM) which have been introduced in 2019. The materials are able to foam by the addition of foaming agents. Foaming materials for FDM printing can be advantageous since they can create lightweight models, and have good impact strength and toughness in relation to their weight (Nofar et al, 2022). The goals of this thesis are to: research the existing knowledge about foaming materials for FDM printing, characterize the different printing parameters that influence the amount of foaming and propose an application for foaming materials for FDM printing. The investigated materials are foaming PLA, ASA, and TPU.
The first goal is reached by conducting a literature review. First, the material properties of foaming materials outside the scope of FDM printing are investigated to better understand the advantages for foaming materials for FDM as well. Second, printing parameters are investigated to understand how these affect final printed products. Third, the available literature for the foaming filaments for FDM printing is investigated. An overview of the material properties in tension is made for the foaming filaments. This shows that most material properties are known for the foaming PLA.
The second goal is reached by conducting three experiments, which investigate the influence of nozzle temperature, fan, printing speed and flow rate. From these experiments it is concluded that the nozzle temperature, printing speed and flow rate influence the expansion of the material, depending on the desired outcome. The fan speed only influences the expansion of the foaming TPU. With the results of these experiments, an overview is made of the influence of the printing parameters on the expansion using the three-link chain model (Doubrovski et al, 2011).
The third goal is reached by conducting a compression experiment in which the foaming PLA is compared with expanded polystyrene (EPS). The results from this experiment and the printing parameters are applied within a motorcycle helmet as demonstrator. This demonstrator shows that the foaming materials for FDM printing could be an interesting area for further research.
This thesis provides a starting point for further research into the influence of printing parameters for foaming materials, as well as the material properties of the foaming filaments. It is recommended to further investigate the influence of more printing parameters on foaming, such as bed temperature, nozzle geometry and type of printer. Second, it is recommended to further investigate the material properties of foaming TPU and ASA as well, since only PLA was tested in the compression experiment. Apart from this, the materials could also be further investigated for tension. Lastly, the proposed foaming PLA sample for the motorcycle helmet could be further investigated for higher strain rates, to confirm the feasibility for the use of motorcycle helmets.
Overall, this thesis investigates the printing parameters for foaming materials which are used to create samples with specific densities for a compression experiment. With the found printing parameters and results from the compression test, a helmet demonstrator is create