ADDITIVELY REINFORCED THERMOFORMING (ART)

Thermoforming is a cost-effective thermoplastic manufacturing process, with short cycle times, and enables the use of 3D-printed or other low-cost molds and preserve surface quality. Some drawbacks to this method include high cost per part relative to injection molding, geometric limitations on the complexity of mold geometries, and inconsistent sheet thickness. The most impactful of these disadvantages is the effect of varying thicknesses, resulting in thin area which act as weak point in the structure. This nonuniformity of the thermoformed material is due to stretching of the polymer as it contacts the mold and begins to cool at a greater rate than the remaining material not in contact. Integrating a reinforcement component to these parts would enable the selective modification of the material behavior during forming and in the final part. The precision and repeatability provided with 3D-printing make it an ideal addition for this application. To illustrate the additively reinforced thermoforming (ART) process, carbon fiber/Polyethylene terephthalate glycol (CF/PETG) is used for the reinforcement of the PETG sheet by selectively printing it on top of the sheet. The evaluation of the ART-formed components and the unreinforced alternative include mechanical characterization of flexural and tensile properties, overall formability, and the effective adhesion and consolidation between layers. The ART-formed samples resulted in a 65.3% and 51.4% increase in flexural and tensile moduli, respectively. The reinforced flexural samples additionally saw a 53% improvement in energy absorption. All composite samples possessed good interfacial adhesion and showed no signs of delamination.