Quasi-Static Characterization of Polyamide-Based Discontinuous CFRP Manufactured by Additive Manufacturing and Injection Molding

Abstract

Generating serial components via additive manufacturing (AM) a deep understanding of process-related characteristics is necessary. The extrusion-based AM called fused layer manufacturing (FLM), also known as fused deposition modeling (FDM™) or fused filament fabrication (FFF) is an AM process for producing serial components. Improving mechanical properties of AM parts is done by adding fibers in the raw material to reinforce the polymer. The study aims to create a more detailed comprehension of FLM and process-related characteristics with their influence on the composite.Thereby, a short carbon fiber-reinforced polyamide (CarbonX™ Nylon, 3DXTECH, USA) with 12.5 wt.‑% fiber content, 7 μm fiber diameter, and 150 to 400 µm fiber length distribution was investigated. To separate process-related characteristics of FLM, reference specimens were fabricated via injection molding (IM) with single-batch material. For the mechanical characterization, quasi-static tensile tests were carried out in accordance to DIN 527‑2. Quality assessment including void content and void distribution was performed via micro-computed tomography (CT).The mechanical characterization clarifies effects on mechanical properties depending on process-related characteristics of FLM. CT scans show higher void contents of FLM specimens compared to IM specimens and void orientation dependent on printing direction. FLM shows process-related characteristics which generally strengthen mechanical properties of polymers. Nevertheless, tensile strength of FLM specimens decrease by more than 28% compared to quasi-homogenous IM specimens.

A review on carbon fiber-reinforced hierarchical composites: mechanical performance, manufacturing process, structural applications and allied challenges

“…But they are also susceptible to lower mechanical properties than conventional fabrication-based CFRP [ 176 ]. The same resultant lower property of 3D-printed CFRP has been rendered by previous studies [ 60 , 177 ]. High porosity combined with the poor interfacial and interlaminar bonding, inadequate infusion of the matrix and the geometry of the nozzle were the impeding factors [ 62 ].…”

Rapid consolidation of 3D printed composite parts using compression moulding for improved thermo mechanical properties

“…% for L-PA6-MEX-±45°-PC and L-PA6-MEX-0°-PC, respectively. Furthermore, the deviation observed in the L-PA6-MEX-0°-PC when compared to L-PA6-MEX ± 45°-PC may be attributed to different raster orientations (Striemann et al , 2019), because the L-PA6 processing in MEX and the compression moulding had similar settings. Comparing the void content quantified in counts·mm −3 , the results for the MEX samples are in a comparable range.…”

Interlayer Bonding Capability of Additively Manufactured Polymer Structures under High Strain Rate Tensile and Shear Loading

“…The material properties of the filament itself are less important, and the process–structure–property relationship results in the AM material properties. The layer-based structure yields anisotropic material behavior [ 6 , 7 ], while different effects of anisotropy are recognizable under quasi-static [ 8 ] and cyclic [ 9 ] loading. Compared to single-batched injection molded polymers, the fracture behavior is also highly anisotropic [ 10 , 11 ].…”