Specific Mechanical Properties of New Hybrid Laminates with Thermoplastic Matrix and a Variable Metal Component

Abstract

Hybrid laminates combine the positive properties of metals and fibre reinforced plastics. Thereby, the relatively free selectable components provide further benefits. Especially thermoplastic matrices offer positive aspects like the possibility of deformation, recyclability as well as the possibility of mass production. To obtain such hybrid laminates the first step is the production of pre-consolidated unidirectional endless fibre reinforced thermoplastic foils. In a second step, these pre-impregnated fibre-foil tapes were alternating thermally pressed with metallic layers in tailored compositions. To use the full capacity of the hybrid laminates an adequate interface between the fibre reinforced thermoplastics and the metallic foil is essential. Different investigations of the authors display the principle possibility to produce hybrid laminates with carbon endless fibre reinforced thermoplastics and aluminium alloy foils. Nevertheless, load free delamination’s occurs. The reason for these delaminations within the interface of the fibre reinforced thermoplastics and the metallic foil are the differences in the thermal expansion coefficient of the components. Caused by the consolidation at elevated temperatures these differences become more significant and reduce the reproducibility of the hybrid laminates. To minimize these thermal induced stresses the graduation of the thermal expansion coefficient is one possibility. This graduation is possible by utilising glass fibre thermoplastic tapes between the aluminium alloy foil and the carbon fibre reinforced thermoplastics. Further investigations are dealing with so called expansion alloys to adapt the thermal expansion coefficient. The latter approach provides the benefit to utilize the full mechanical properties of the carbon fibre reinforced thermoplastics and to economize the glass-fibre tapes. Nevertheless, these expansion alloys are characterized by a high density. Hence, within this contribution the specific mechanical properties as well as the advantages and disadvantages of hybrid laminates with expansion alloys or aluminium alloys with glass-fibre thermoplastics interlayers are discussed and assessed. These specific mechanical properties display the potential of the expansion alloy in spite of the high density by means of comparable values. The sample only consisting of carbon fibre reinforced plastics highlights the great variety and possibilities of different hybrid laminate structures and combinations regarding the thickness and positioning of the component layers.