Process Parameter Effects on Interlaminar Fracture Toughness of FDM Printed Coupons
In Fused Deposition Modeling (FDM), filaments of heated thermoplastic are extruded from a tip that moves in a raster-like motion. Depending on filament material properties and the processing parameters, the extruded beads and the fusion-bond between them
- PDF / 1,072,961 Bytes
- 9 Pages / 595.276 x 790.866 pts Page_size
- 117 Downloads / 191 Views
Process Parameter Effects on Interlaminar Fracture Toughness of FDM Printed Coupons G.P. Tandon, T.J. Whitney, R. Gerzeski, H. Koerner, and J. Baur Abstract In Fused Deposition Modeling (FDM), filaments of heated thermoplastic are extruded from a tip that moves in a raster-like motion. Depending on filament material properties and the processing parameters, the extruded beads and the fusion-bond between them could result in anisotropic properties (particularly with regard to strength). In this work, the focus is on characterizing the interlaminar fracture toughness of coupons produced by FDM with varying road-to-road offsets producing positive, zero and negative air gaps between neighboring roads resulting in coupons of varying density (void content). The resulting bond line formation is assessed through measuring and analyzing changes in the mesostructure and the contact attained at the interfaces between the adjoining roads. The bond quality is assessed by evaluating plane-strain fracture toughness using compact tension specimens. Results demonstrate an approximate five-fold increase in fracture toughness with varying air gaps. Keywords Additive manufacturing • Fused deposition modeling • Ultem*9085 • Fracture toughness • Air gap
8.1
Introduction
Additive manufacturing (AM) technologies such as FDM provide a means of producing parts of complex, 3-D geometry [1] by depositing material layer-by-layer. As successive layers are built up, new molten material will heat previously deposited roads causing their outer surfaces to melt. The formation of bonds among polymer filaments in FDM parts is driven by the thermal energy of the extruded material. The bonding quality depends on the growth of the neck formed between the adjacent filaments and on the molecular diffusion and randomization of the polymer chains across the interface. The bonding phenomenon is thermally driven and determines the integrity and mechanical properties of the resulting structure [2]. Suspected reasons include the presence of voids inherent to the FDM process (creating stress concentration and crack initiation sites) and the thermal history to which the material is exposed during the process (leading to large residual stresses). Test results also show that the mechanical strength properties depend on the given inner part structure as a result from the build direction and the toolpath generation [3]. The fact that the mechanical properties of the part depend on the orientation and path becomes particularly critical when FDM technology is used to produce components directly for end use [4]. The quality of FDM processed parts mainly depends on careful selection of process variables. Thus, identification of the FDM process parameters that significantly affect the quality of FDM processed parts is important [5]. FDM structures built with rasters (beads of material) oriented at bias angles to the primary axis of the structure morphologically resemble laminated composite materials. The “laminate analogy” and respectively application of classical lami
Data Loading...
