Formability and Performance of Steel-Plastic-Steel Laminated Sheet Materials

Steel-plastic-steel (SPS) laminated sheet materials can be utilized in certain automotive applications to achieve significant weight savings over “conventional” sheet steels. Three SPS laminates were produced using various combinations of light gage steel skins and polypropylene cores. Compared to homogeneous steels, density reductions of 35 to 46 percent were achieved. Benefiting from the ductility of their steel skins, SPS laminates can posses adequate formability for typical automotive sheet applications. Furthermore, the forming limit curves can be predicted using the work hardening exponent and thickness of the composite laminate. In three-point bending, the elastic stiffness of SPS laminates is nearly equivalent to that of monolithic steels of the same thickness. Thus, weight reductions similar to those of aluminum alloys can be achieved utilizing laminates in stiffness-critical applications. The quasi-static dent resistance of SPS laminates is improved by increasing the plastic core thickness, by increasing the steel skin strength, and by utilizing bake hardenable steel skins. These results provide an indication of the suitability of SPS laminates for potential use in automotive applications.