Improving the Accuracy of Deep Drawn Fiber-Metal Laminate Parts by Preliminary Surface Treatment

Abstract

In the present study, fiber-metal laminates (FMLs) were formed by deep drawing after the metallic component was pretreated by laser structuring, sandblasting or anodizing in order to reduce the height of process-related wrinkles. Such surface texturing is commonly performed to improve the bond strength between the adhesively joined components of the FML by selectively increasing the surface area. This results in improved stability of the finished FML part due to increased resistance to delamination. First, the adhesion properties induced by each process were quantified using shear tensile tests. The shear strength was increased for all processes compared to the unstructured surface. The surface structures were characterized by roughness measurements and scanning electron micrographs. The surface properties adjusted by the different processes also contributed to the part accuracy of the deep-drawn FMLs. During forming, the matrix material contained in the unidirectional fiber composite plastic tends to build up against the forming direction, resulting in wrinkling between the flange and the cup shell. The increased adhesive strength of the metallic component impedes the flow of the matrix material and decreases the height of the resulting wrinkles. The height of the wrinkles was determined using a coordinate measuring machine on the formed FML cups.