Part strength evolution with bonding between filaments in fused deposition modelling

Abstract

The present work investigates, by both mathematical modelling and experiment, the contribution of bonding between the filaments to the strength of the parts manufactured by fused deposition modelling (FDM). A mathematical model for neck growth between cylindrical filaments is derived based on viscous sintering for cylindrical filaments. Theoretical ultimate tensile load is determined from the layer thickness information and predicted average final neck size between filaments. The experimental ultimate tensile load is obtained by conducting a simple tension test with two different build directions. Agreement between theoretical and experimental ultimate tensile load and scanning electron microscope (SEM) photomicrographs of the fracture surface indicate that the strength of the FDM part is primarily due to intra-layer bonding, interlayer bonding and neck growth between filaments. It also indicates that the total time and heat available to the filaments are just sufficient to grow necks but not enough to fully coalesce.

Microstructure, Thermal and Mechanical Behavior of 3D Printed Acrylonitrile Styrene Acrylate

“…Thus, the result achieved for the tensile strength reflects more the effect of the in‐plane deformation through the −45°/+45° layups for which the intra‐layer bond is a major contributor in tensile response. The result obtained by Gurrala et al shows that the activation of the intra‐layer deformation mechanism (filaments aligned with the loading direction) leads to a ductile‐type failure against inter‐layer mechanism (layers normal to the loading direction), which enhances the brittle‐type failure. In addition, several studies demonstrate that the lowest tensile strength is achieved for vertical build orientation (loading direction aligned with the building direction) .…”

On Surface Finish and Dimensional Accuracy of FDM Parts after Cold Vapor Treatment

“…A temperature regulated extrusion head consists of liquefier nozzle that extrudes the semiliquid thermoplastic material and deposits in form of precise layers over a fixtureless base table [2]. The temperature inside the chamber is maintained lower than the melting temperature of the filament therefore, the deposited filament rapidly solidify when adhered to the previous layer thus involving highly transient heat transfer process [3].…”

An insight to the failure of FDM parts under tensile loading: finite element analysis and experimental study

“…The effect of building direction and model interior on volumetric shrinkage and tensile strength was investigated for FDM parts using multi-objective optimization technique [13]. They further investigated the effect of inter-layer bonding, intra-layer bonding and neck formation between adjacent filaments on tensile strength of FDM parts using both experimental and mathematical modeling [14]. They observed that in a FDM sample with 0° raster layers the failure of a specimen is due to inter-layer fracture whereas in 45° raster layers, specimen fails under both inter-layer and intra-layer fracture.…”