Additive manufacturing of soluble cores for composite manufacturing

Abstract Additively manufactured soluble cores enable the production of hollow composite components with complex internal geometries, but materials specifically developed for sacrificial composite tooling may be costly for prototype and low-volume applications. This work investigates the process feasibility of Stratasys SR-30, a soluble support material for fused deposition modelling (FDM) not originally developed for composite tooling, as a sacrificial core for low-temperature autoclave curing. A feasibility-oriented experimental campaign was conducted on cylindrical cores with different aspect ratios, double-diameter transitions, a horseshoe geometry and an automotive brake-cooling duct, considering different temperatures, pressures, isothermal holding times and internal infill architectures. At 90 $$^\\circ $$ C, core stability depended strongly on the internal architecture. The more robust configuration retained its geometry up to 4 bar, whereas the lower-material configuration showed localised deformation at 3.5 bar and partial collapse at 4 bar. All three specimens tested at 110 $$^\\circ $$ C and 3.5 bar exhibited severe non-axisymmetric deformation. Differential scanning calorimetry (DSC) showed that the 90 $$^\\circ $$ C cycle lies slightly above the upper bound of the glass-transition-related range measured for printed SR-30, consistent with the observed pressure- and architecture-dependent stability. Internal surface roughness was evaluated on representative single-ply woven laminates, while optical microscopy was performed on four-ply laminates as a qualitative process-validation step. A preliminary direct-cost comparison was also performed for a prototype-scale case. The results define an experimentally supported processing window for using SR-30 cores in low-temperature autoclave manufacturing, while highlighting the limitations associated with temperature, pressure and infill architecture.