Metal Foams with Advanced Pore Morphology (APM)

Abstract

In many applications metal foam is used as light weight filler material e.g. to improve energy absorption, to reduce body sound/vibration or simply to act as lightweight core layer for increased bending performance of sandwiches. In this paper the Advanced Pore Morphology (APM) process particularly developed for these applications is described. The APM process is based on the powder metallurgical foaming process. The APM approach separates foam expansion from part shaping. Complex shaped APM foam parts are made from numerous small volume standard geometry foam elements, which are joined in a separate step e.g. by adhesive bonding. Producing small volume standard geometry foam elements is a simple and robust process. As a result, each APM foam element has a homogeneous pore morphology. By using different types of foam elements and joining processes new degrees of freedom in the adjustment of properties are opened. In a first test series APM foam parts and filled extrusion profiles have been characterized. Test results are displayed and discussed. Due to the bulk character fully automated APM foam mass production in (customized) standard equipment (handling, belt furnace, etc.) is possible. The APM approach allows for maximum flexibility and fast technology transfer. One type of foam element can be used for various different foam parts. End-users are able to produce foam filled structures without any metal foam expansion know how. After supply of adhesive coated (but non tacky) foam elements, e.g. from Fraunhofer IFAM, the end-user pours the foam elements into the cavity to be APM foam filled. The APM filling is finished by heat treatment at e.g. 200 °C, which activates and cures the adhesive coating. In total the APM process leads to drastically reduced production costs especially for metal foam fillings in hollow structures.