Mechanical characterisation of PA-Al2O3 composites obtained by SLS

The increasing need for strongly personalized products, to be produced in few parts with short time-to-market, makes Rapid Tooling and Manufacturing competitive with respect to traditional processes.The great advantages, in terms of reduced times and costs for the product’s launching, can be properly exploited only through a deep knowledge concerning the parts’ performances as a function of the process parameters. A promising material for application in SLS technology is polyamide composite (PA-Al2O3). An experimental campaign was started and some specimens, with different orientations in regard to powder deposition plane and laser path, have been manufactured and tested. Mechanical properties have been determined using tensile test performed both at room temperature and at 100 °C.The sintered material shows an evident main anisotropy between the growth direction (z axis) and the plane XY, as well as in this plane the parts seem to be not sensitive to the sintering direction at room temperature (x, y, xy). At 100°C the effect of sintering direction on XY plane becomes more evident and a different behaviour results considering x and y direction respectively (secondary anisotropy). Scanning Electron Microscopy (SEM), Atomic Force and Lateral Force Microscopy (AFM and LFM) have been carried out to understand the effect of the manufacturing anisotropy on the mechanical performances, both in terms of additive construction and laser sintering strategy. The observation of the rupture surfaces showed that at room temperature cracks originate from the external surface and propagate initially by the ductile failure of the polymeric matrix, up to the sudden fracture of the whole section