Investigations of the carbon fibre cross-sectional areas and their non-circularities by means of laser diffraction

Laser diffraction is a commonly used tool to measure the fibre diameter of carbon fibres prior to mechanical testing. However, non-circularities of carbon fibres need to be considered in order to minimise measuring errors. As the work at hand demonstrates, using a single measurement of the fibre diameter may cause deviations as high as 30% from a computationally determined value. It appears that the error can be minimised by acquiring a data set of several apparent diameters as a function of the angle around the fibre axis. Based on this data, the cross-sectional area can be calculated as a circle with an averaged diameter or as an ellipse by applying an elliptical fitting procedure

Fused filament fabrication: Comparison of methods for determining the interfacial strength of single welded tracks

The mechanical properties of plastic-based additively manufactured specimens have been widely discussed. However, there is still no standard that can be used to determine properties such as the interfacial strength of adjacent tracks and also to exclude the influence of varying manufacturing conditions. In this paper, a proposal is made to determine the interfacial strength using specimens with only one track within a layer. For this purpose, so-called single-wall specimens of polylactide were characterised under tensile load and the interfacial area between the adjacent layers was determined using three methods. It turned out that the determination of the interfacial area via the fracture surface is the most accurate method for determining the interfacial strength. The measured interfacial strengths were compared with the bulk material strength and it was found that the bulk material strength can be achieved under optimal conditions in the FFF process. It was also observed that with increasing nozzle temperature, the simultaneous printing of specimens influences the interfacial strength. To conclude, this method allows to measure the interfacial strength without superimposing the influence of voids. However, for example, the interfacial strength within a layer cannot be determined

Investigations of the carbon fibre cross-sectional areas and their non-circularities by means of laser diffraction

Abstract Laser diffraction is a commonly used tool to measure the fibre diameter of carbon fibres prior to mechanical testing. However, non-circularities of carbon fibres need to be considered in order to minimise measuring errors. As the work at hand demonstrates, using a single measurement of the fibre diameter may cause deviations as high as 30% from a computationally determined value. It appears that the error can be minimised by acquiring a data set of several apparent diameters as a function of the angle around the fibre axis. Based on this data, the cross-sectional area can be calculated as a circle with an averaged diameter or as an ellipse by applying an elliptical fitting procedure.</jats:p

Fused filament fabrication: comparison of methods for determining the interfacial strength of single welded tracks

The mechanical properties of plastic-based additively manufactured specimens have been widely discussed. However, there is still no standard that can be used to determine properties such as the interfacial strength of adjacent tracks and also to exclude the influence of varying manufacturing conditions. In this paper, a proposal is made to determine the interfacial strength using specimens with only one track within a layer. For this purpose, so-called single-wall specimens of polylactide were characterised under tensile load and the interfacial area between the adjacent layers was determined using three methods. It turned out that the determination of the interfacial area via the fracture surface is the most accurate method for determining the interfacial strength. The measured interfacial strengths were compared with the bulk material strength and it was found that the bulk material strength can be achieved under optimal conditions in the FFF process. It was also observed that with increasing nozzle temperature, the simultaneous printing of specimens influences the interfacial strength. To conclude, this method allows to measure the interfacial strength without superimposing the influence of voids. However, for example, the interfacial strength within a layer cannot be determined