State-of-the-art of fiber-reinforced polymers in additive manufacturing technologies

Abstract

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Evolution of additively manufactured injection molding inserts investigated by thermal simulations

“…Past elaborations on the mechanical stability of fiber-reinforced PhP IM inserts [4] have shown an increased lifetime due to a significantly reduced crack propagation velocity. This allows for the further development in step 3 where (1) geometrical scales are significantly larger, (2) cavities and therefore the volume of injected polymer are bigger, (3) the contact surface between the injected polymer and the insert is increased, and (4) warping due to the VP process is (a) increased in the process and (b) more significant due to the larger geometries. All factors result in higher stresses due to thermally introduced internal stresses, and stresses due to limitations of space in the standardized mold, which need to be accounted for by the manufacturing and post-processing of the insert.…”

“…[7]) indicate that the choice of fiber material significantly influences the thermal conductivity of the final material. Challenges in the fiber-matrix interface as mentioned in [2] as well as fiber orientation [8,9], which also influences the crack propagation, will need to be accounted for.…”

“…Injection molding (IM) inserts made by additive manufacturing (AM) rapid prototyping (RP) such as vat photo polymerization (VP) are already state of the art as discussed in [1][2][3][4] combining advantages in product design cycle time, manufacturing complexity, environmental impacts, as well as a certain freedom of shape which comes with the AM process. IM inserts are produced from thermoset photopolymers (PhPs) and then mounted into a standardized mold, which is usually manufactured from steel in a traditional way or by novel metal AM processes allowing for a more complex cooling system.…”

Internal fiber structure of a high-performing, additively manufactured injection molding insert

“…[1] Previously discussed fiber-reinforced injection molding (IM) inserts have proven to reduce the process and design cycle of IM parts by one order of magnitude due to flexibility in design [2], production speed, digital capacities, and cost efficiency [3]. Research presented in [4][5][6][7] has utilized short, virgin, and unsized carbon fibers (CF) with diameters of 7.2 μm and average lengths of 100 μm, which increased the lifetime of those inserts by a factor of 20 up to 4,500 to 4,600 shots per insert with 5 to 10 % in weight of CFs. By improving the fiber-matrix-interface and optimizing process parameters in both the additive manufacturing (AM) vat photopolymerization (VP) process as well as the IM cycle with additional cooling mechanisms (both forced and free convection) [4], the lifetime of the named inserts has been improved up to 4,500 shots.…”

“…Research presented in [4][5][6][7] has utilized short, virgin, and unsized carbon fibers (CF) with diameters of 7.2 μm and average lengths of 100 μm, which increased the lifetime of those inserts by a factor of 20 up to 4,500 to 4,600 shots per insert with 5 to 10 % in weight of CFs. By improving the fiber-matrix-interface and optimizing process parameters in both the additive manufacturing (AM) vat photopolymerization (VP) process as well as the IM cycle with additional cooling mechanisms (both forced and free convection) [4], the lifetime of the named inserts has been improved up to 4,500 shots. A significant challenge mentioned in several investigations [5,8] was introduced by the layer-wise orientation of CFs due to process parameters including build plate movement and print orientation, as well as flow patterns.…”