Ultra-high-strength micro-mechanical interlocking by injection molding into laser-structured surfaces

Surface structuring provides the ability to generate new strong composite materials by employing micro-mechanical interlocking (MMI). The present state-of-the-art in composite materials is often based on advanced chemical bonding along with simple roughening of the surface, while the use of a specifically designed surface topography has been given much less consideration. The adhesive-based techniques may, however, not provide bonding that exhibits sufficiently high mechanical strength as well as a high tolerance to temperature changes that is essential for many industrially relevant situations. In the present paper, recent results from the optimization of material interlocking properties by laser-based surface microstructuring are reported. The laser-based structuring provides much flexibility in the geometry of the interface, and a high strength is ensured by directly injection molding a plastic into the laser-structured surface. The dependence of the mechanical strength of the joint on the exact laser generated surface morphology is investigated. It is shown that appropriate surface structuring can increase the bonding strength by several orders of magnitude, yielding interlocking of very high mechanical stability.