Microscopic Phenomenology of Plastic Deformation in Polymer-Metal Laminates
- PDF / 309,208 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 29 Downloads / 203 Views
Microscopic phenomenology of plastic deformation in polymer-metal laminates. W.P.Vellinga, R.Rastogi and H.E.H.Meijer, Materials Technology, Mechanical Engineering, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, the Netherlands. ABSTRACT Microscopic studies of the plastic deformation of a simple polymer-metal laminate (PETsteel) are outlined. Representative examples of deformation and failure modes are illustrated with qualitative results from birefringence microscopy. The relation between bulk PET mechanical behaviour and laminate properties is discussed. INTRODUCTION Polymer-metal laminates are increasingly used in forming processes that were previously the exclusive domain of metals, such as deep-drawing or wall-ironing (for example in the shaping of beverage cans or car body parts). Elastic moduli of both constituents, adhesion at the interface as well as the accessible plastic deformation mechanisms and the resulting microstructure are of importance. A coherent (microscopic) picture of the interplay of deformation mechanisms determining the processing limits of a laminate, is lacking. We aim at obtaining such an experimental record by performing deformation experiments and studying the evolution in microstructure with several types of microscopies, in-situ as well as ex-situ, in particular polarisation (birefringence) reflection optical microscopy. Confocal Laser Scanning Microscopy and Atomic Force Microscopy are also employed but are outside the scope of the current paper. These techniques cover both a wide range of length scales as well as physical contrast modes. It is expected to be useful in understanding and possibly controlling mechanisms that lead to failure such as interface delamination. Furthermore these data may be useful in guiding efforts to calculate the deformation behaviour or deformation limits of such laminates. EXPERIMENT The experimental work consists of investigations into the bulk properties of PET as well as the laminate properties. Two types of PET are being used, pellets of a slowly crystallising PET, PET9921w (Eastman) and a non-crystallising, modified PET, PETG 6737 (Eastman). Studies of the bulk involve uniaxial compression and tensile deformation to large strains, with PET that has undergone simple annealing treatments starting from the glassy state as well as from the melt. Here we only discuss material derived from the glassy state. Wide Angle X-ray Scattering (WAXS) studies of the resulting crystalline structures and their mechanical behaviour under high hydrostatic loads have been performed. Detailed results of those experiments will be reported elsewhere, however in the scope of this paper the WAXS studies have allowed us to calibrate qualitative values of crystallinity derived from Fourier Transform InfraRed spectroscopy (FTIR). L1.9.1
Bulk and thin film PET9921w samples were quenched from melt and subsequently annealed for 10 minutes at various temperatures above as well as below the cold crystalisation temperature Tcc (120 °C). Employing thickness fri
Data Loading...
