Mechanical characterization of hybrid material systems consisting of sheet metal and advanced composites

Strip-shaped hybrid coupon specimens comprised of steel and glass/carbon fiber reinforced plastics are tested under quasistatic tension and 3-point-bending. The effects of major material and design parameters (steel and fiber type, laminate thickness and layup) on the stiffness, strength and the specific energy absorption are assessed. Furthermore, hybrid mechanisms resulting from the mutual interaction of both constituent materials are presented. Although anticipated effects on the hybrid specimens' stiffness and strength are widely confirmed, the fiber type for example exhibits a distinctly smaller impact than expected. The specimens' loading and failure behavior is rather dominated by the type of steel and its characteristics. Thus, glass fiber reinforced hybrid variants generally keep up with carbon fiber reinforced hybrid variants in terms of mechanical properties. Considering the difference in price, this is of particular interest for hybrid mid or high volume crash structural applications. As hybrid mechanism, a distinct extension of the maximum strain is observed for both composites (up to 48 %) and steel (up to 23 %) when joined in a hybrid specimen and tested under tensile loads. Furthermore, having composites on the rather pressure loaded side in 3-point-bending results in a 26 %-increase in mass specific energy absorption (compared to reverse loading) due to an enhanced composite failure mode and the stabilizing effect of the steel strip.