FUNDAMENTO SISTEMA DE AGRUPAMIENTO

Additive manufacturing as a new technology for making mechanical parts opens news possibilities within the area of SFRP composites.

This technology loosen the constraints imposed by traditional manufacturing techniques during the design phases. Moreover, the new available design freedom match perfectly with topological optimization software which improves and enhances mechanical designs. Furthermore, the results from the mathematical algorithms can have now a physical materialization, opening a new paradigm in engineering design.

Additionally, the combination of these techniques with cutting-edge FEA simulations in which material micro-models as manufacturing processes can be accurately simulated, delivers a set of powerful CAE tools for evaluation purposes.

Additive manufacturing of SFRP composites can deliver lighter parts in which design specifications can be still accomplished. Topology optimization sets the dichotomy between having lighter parts and having stronger parts. In mechanical parts with low criticalities, these alternatives can be really interesting in order to get a cost saving due the mass reduction during design. It is especially amusing in the aero-spatial or the automotive industries where mass reduction downgrade additional costs regarding fuel saving.

These accurate tools make the strength of materials to be pushed into its limits getting parts using less material while achieving its design goals. Following with this idea with iterative design cycles, the gap between the addition of extra materials with conservative methods and the use of exact amount of material can be shortened.

Even then, the inclusion of this new manufacturing technology for the SFRP composite science, brings new challenges to face.

The AM process is still far from being mastered and final parts quality need a substantial improve. In order to do so, controlling parameters of the printing chamber as chamber temperature, nozzle printing temperature or the cooling system will allow to improve the final quality of the part. The printing process must be mastered in order to reduce as maximum air inclusions within the printed part.

Furthermore AM is not totally design constraint free. It is true that it removes several limitations of the traditional methods but it introduces another ones that have to be faced. One of them is to think in advance the correct utilization and removal of supports during the printing and post- printing phases. Actually, not all geometries can be manufactured with AM. Complex hollowed shapes like the one presented in this work will bring several issues for remove properly the supports after the part is completed. This is something that the designer will have to bear in mind during the design phases.

Additional challenges to increase the adhesion between layers are ahead. The control of the temperature where the material is deposited in each layer will reinforce the material adhesion. It has been exposed how the filament orientation can be controlled during the printing process with the definition of a toolpath. The fibers tend to get aligned to the path followed by the extruder nozzle, which is really important in order to control the local strength of the printed part. Controlling this can make long-lasting and stronger parts in parallel directions to the load application as if they would had been manufactured in injection moulding.

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The definition of the toolpath to get fibers aligned in the desired direction is critical. Similarly, this was done for the FOD tensor during injection moulding simulations, for AM the toolpath will determine the filament orientation and therefore the fiber orientation as well.

A powerful topology optimization software is critical to obtain better design results. Stable and powerful optimization tools are usually integrated with other powerful software which are more expansive than most of the commercial CAE software. This requires an investment if an improvement of this way of making engineering design is desired.

The cost of manufacturing with AM are significantly lower than with injection moulding. Using AM, do not require to use an injection moulding machine and a part mould. Besides, IM is an expensive technology which feasibility is possible thanks to scale economies. Taking profit from AM will save this great investment. A good commercial FFF AM machine for unfilled polymers or SFRP composites is a cheaper investment than the machine for IM.

Using a different initial material distribution as the input for the topology optimization would release different solutions. It has to be explored different alternatives starting from different geometries. In this way, the algorithm will be working in different directions and ending up with a diverse element connectivity and therefore, a particular element reorganization.

To conclude, new Digimat versions of AM and RP will allow to integrate the toolpath within a single model, as well as initial stresses and warpage. Displaying in the same model all the results will give a better approach of the actual behaviour of the part. The inclusion of the initial stresses into the model will decrease the maximum strength of the part, being able to bear less stress coming from external loads.

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