How did our process overcome the problem of mechanical performance and manufacturing capability?
First of all, the AREVO process starts with a superior quality filament with high-fiber content, homogeneous distribution of fibers, and low-void content (<2%) (Figure 4), which guarantees high modulus and strength.
Then, in the deposition process, instead of a heated nozzle that is typically used in the material-extrusion processes, a laser is adopted to provide rapid heating, which makes it a Direct Energy Deposition (DED) process. A compaction roller compresses the filaments with sufficient pressure to eliminate the voids inside and in between layers, and consolidates the parts in-situ. Detailed studies of the characteristic control of the deposition system were conducted to tailor the optimum process parameters for any given material and geometrical features, to obtain good interlayer adhesion and consolidation. This moves the technology from prototyping to manufacturing.
The following schematics in provide a visual comparison between the two general process types, as well as an overview of the advantages and disadvantages.
AREVO’s DED process
Material Extrusion (FDM) processes
With the AREVO system, a much higher strength is achieved, which can be seen by comparing Brenken’s and AREVO’s data in Figure 1 and Figure 2. It is the only process that eradicates all the defects from the material and the processing, such as voids, resin rich areas, insufficient compaction, degree of cure (for thermosets only). All of these issues have a detrimental effect on the mechanical performance of the components. Therefore, autoclaved composite parts show the highest strength and stiffness.
The blue bars in Figure 6 show the tensile properties of AREVO’s process compared to the same material and fiber content processed in an autoclave. The tensile modulus for both the unidirectional (UD) and quasi-isotropic (QI) materials are comparable to the autoclaved. The tensile strength of UD and QI materials achieved 80% and 70% of those of the autoclaved parts, respectively. This is even better than most out-of-autoclave (OOA) composite materials, which typically achieve less than 70% of the autoclaved strength.
With the excellent material properties, the AREVO DED process combines the advantages of additive manufacturing such as bridging (without support structure), overhangs and (in particular) load path optimized fiber path, with in-situ consolidation of high performance lightweight composite structures, without additional post-consolidation or curing. This provides tremendous benefits for the manufacturing of a large variety of engineering structural parts and, finally, brings the value of AM to manufacturing at scale.