Abstract
Fiber-reinforced 3D printing technology offers significant improvement in the mechanical properties of the resulting composites relative to 3D printed (3DP) polymer-based composites. However, 3DP fiber-reinforced composite structures suffer from low fiber content compared to the traditional composite, such as 3D orthogonal woven preforms solidified with vacuum assisted resin transfer molding (VARTM) that impedes their high-performance applications such as in aerospace, automobile, marine and building industries. The present research included fabrication of 3DP fiberglass-reinforced nylon composites, with maximum possible fiber content dictated by the current 3D printing technology at varying fiber orientations (such as 0/0, 0/90, ±45 and 0/45/90/−45) and characterizing their microstructural and performance properties, such as tensile and impact resistance (Drop-weight, Izod and Charpy). Results indicated that fiber orientation with maximum fiber content have tremendous effect on the improvement of the performance of the 3DP composites, even though they inherently contain structural defects in terms of voids resulting in premature failure of the composites. Benchmarking the results with VARTM 3D orthogonal woven (3DOW) composites revealed that 3DP composites had slightly lower tensile strength due to poor matrix infusion and voids between adjacent fiber layers/raster, and delamination due to lack of through-thickness reinforcement, but excellent impact strength (224% more strong) due to favorable effect of structural voids and having a laminated structure developed in layer-by-layer fashion.
Highlights
Composites revealed that 3D printed (3DP) composites had slightly lower tensile strength due to poor matrix infusion and voids between adjacent fiber layers/raster, and delamination due to lack of throughthickness reinforcement, but excellent impact strength (224% more strong) due to favorable effect of structural voids and having a laminated structure developed in layer-by-layer fashion
Reinforcing with continuous fiber posed a great challenge, requiring to change in the configuration of the printer: either two separate supply systems for polymer and fiber, but a single extrusion process, or supplying and extruding polymer and polymer pre-impregnated fiber separately using a dual nozzle system [3]. The latter is preferred for its improved fiber–polymer interfacial property and desired fiber placing facility, the coaxial extrusion configuration can have high fiber content with relatively poor interfacial bonding between fiber and polymer that resulted in poor mechanical performance and premature failure of composites [3]
Apart from the void of the inherent supply materials, a significant amount of voids were found in the case of the fused deposition modeling (FDM) 3DP part due to its fashion of building a part [3]
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Reinforcing with continuous fiber posed a great challenge, requiring to change in the configuration of the printer: either two separate supply systems for polymer and fiber, but a single extrusion process ( called coaxial extrusion process), or supplying and extruding polymer and polymer pre-impregnated fiber separately using a dual nozzle system [3] The latter is preferred for its improved fiber–polymer interfacial property (good adhesion between fiber and polymer) and desired fiber placing facility, the coaxial extrusion configuration can have high fiber content with relatively poor interfacial bonding between fiber and polymer that resulted in poor mechanical performance and premature failure of composites [3]. The present research involved maximizing 3DP fiberglass-reinforced composites at different fiber orientations (0/0, 0/90, ±45 and 0/45/90/−45) and exploring their impact properties (Drop-weight, Izod and Charpy impacts), including tensile behavior, with a focus on the failure mechanism. Among the three major types of impacts, Charpy and Izod impacts are called pendulum impacts providing information about a material’s toughness, while the Drop-weight impact provides more information about the behaviors of material, such as longitudinal wave transmission, load distribution, peak force, peak energy and total energy absorption [15]
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