The Essential Work of Fracture parameters for 3D printed polymer sheets

Abstract

Additive manufacturing is becoming increasingly popular in academia and industry.Accordingly, there has been a growing interest in characterizing 3D printed samples to determine their structural integrity behaviour. We employ the Essential Work of Fracture (EWF) to investigate the mechanical response of polymer sheets obtained through additive manufacturing. Our goal is twofold; first, we aim at gaining insight into the role of fibre reinforcement on the fracture resistance of additively manufactured polymer sheets. Deeply double-edge notched tensile (DDEN-T) tests are conducted on four different polymers: Onyx, a crystalline, nylon-reinforced polymer, and three standard polymers used in additive manufacturing -PLA, PP and ABS. Results show that fibrereinforcement translates into a notable increase in fracture resistance, with the fracture energy of Onyx being an order of magnitude higher than that reported for non-reinforced polymers. On the other hand, we propose the use of a miniature test specimen, the deeply double-edge notched small punch specimens (DDEN-SP), to characterize the mechanical response using a limited amount of material. The results obtained exhibit good alignment with the DDEN-T data, suggesting the suitability of the DDEN-SP test for measuring fracture properties of additively manufactured polymers in a cost-effective manner.

Manufacturing process-driven structured materials (MPDSMs): design and fabrication for extrusion-based additive manufacturing

“…PLA has a low glass transition temperature (60°C–70°C typically) and the MPDSM structure could weaken as the temperature rises, causing creep (in the best case) or disintegration (in the worst case). This is the reason that the raster-45° configuration is commonly used for PLA; it is generally considered to be the most stable configuration (Patterson et al , 2019; Ahmed and Susmel, 2017; Song et al , 2017; Cuesta et al , 2019; Papon and Haque, 2019).…”

“…However, there are the following three major issues with this approach for the problem at hand: First, the having all of the fibers facing in the same direction of the load may decrease the stiffness of the clip significantly due to fiber relaxation and pullout. Next, every layer in the structure would be a series of concentric rings, so any small manufacturing defects or fiber relaxation could case it to collapse. PLA has a low glass transition temperature (60°C–70°C typically) and the MPDSM structure could weaken as the temperature rises, causing creep (in the best case) or disintegration (in the worst case). This is the reason that the raster-45° configuration is commonly used for PLA; it is generally considered to be the most stable configuration (Patterson et al , 2019; Ahmed and Susmel, 2017; Song et al , 2017; Cuesta et al , 2019; Papon and Haque, 2019). …”

The Use of Various Measurement Methods for Estimating the Fracture Energy of PLA (Polylactic Acid)

“…Nevertheless, it can sometimes be adopted in other geometries. For example, EWF methodology can be used in deeply double-edge notched small punch (DDEN-SP) test [ 14 ] and single-edge notched bending (SENB) as well [ 15 ]. EWF can be a simple alternative method for the J-integral under plane strain conditions.…”

Essential work of fracture assessment of acrylonitrile butadiene styrene (ABS) processed via fused filament fabrication additive manufacturing

“…A decrease of 11% was observed in fracture toughness for printing orientation of 0/90°compared to + 45/− 45°. Recently, Cuesta et al [44] used the essential work of fracture (EWF) approach to examine the mechanical behaviour and fracture properties of 3D-printed polymeric materials, including fibre-reinforced plastics, and proposed a new miniature test specimen for measuring the fracture properties of polymers processed via AM. Moreover, Lorenzo-Bañuelos et al [45] examined the effect of raster orientation on the fracture properties of thin polypropylene (PP) components processed via material extrusion AM, and found that the printing orientation can have a significant effect on the essential work of fracture of the 3D-printed PP.…”