Research article

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

¹ Karlsruhe Institute of Technology, Institute for Applied Materials – Materials Science and Engineering (IAM-WK), Kaiserstrasse 12, 76131 Karlsruhe, Germany
² TU Dortmund University, Department of Spatial Planning, August-Schmidt-Straße 10, 44221 Dortmund, Germany
³ Fraunhofer Institute for Chemical Technology (ICT), Joseph-von-Fraunhofer-Straße 7, 76327 Pfinztal, Germany

^* e-mail: anselm.heuer@kit.edu

Received: 29 September 2021
Accepted: 29 November 2021

Abstract

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.