EFFECTIVE TENSILE STRENGTH OF ADDITIVELY MANUFACTURED DISCONTINUOUS CARBON FIBER-REINFORCED POLYMER VIA COMPUTED TOMOGRAPHY

摘要

The initial phase of extrusion-based additive manufacturing (AM) methods like fused layer manufacturing (FLM), fused deposition modeling (FDM), and fused filament fabrication (FFF) is characterized by prototyping. Due to improvements in technology, process, and material such as reinforcing the polymer, applications change to manufacturing final parts. The aim of this study is a detailed comprehension of process-related characteristics and the corresponding influence on the composite. Hence, a discontinuous carbon fiber-reinforced semi-aromatic polyamide (CarbonX Nylon, 3DXTECH, USA) was applied. The filament has a fiber content of 12.5 wt.-%, the fiber diameter is 7 μm by a typical length of fibers between 150 and 400 μm after fabrication to filaments. Separating process-related characteristics of FLM, reference specimens were fabricated via injection molding (IM) with single-batch material. Quasi-static tensile tests were executed for mechanical characterization. Void volume content and void distribution were analyzed via micro-computed tomography (CT). In further processing steps, micro-CT data were investigated by image processing receiving the void area share in the cross-sectional area. Taking the adapted cross-sectional area into account, the effective tensile strength of additively manufactured composite is calculated. The investigations show higher tensile strength, lower void content and smaller standard deviation of IM specimens compared to FLM. Process-related characteristics of FLM result in an alignment of voids in dependency of printing direction and a volume void content up to 6.5%. The adjustment of the cross-sectional area influences the tensile strength positively by an increased effective tensile strength up to 14%.