MECHANICAL BEHAVIOR OF LAYERED CERAMIC-POLYMER MICROSTRUCTURES

Stephen J. Bennison and Anand Jagota

Central Research & Development

E.I. DuPont de Nemours & Co. Inc.

Wilmington, DE 19880-0356

Assemblies of ceramic and polymer phases in layered microstructures demonstrate unique mechanical behavior. The combination of a hard, brittle phase with a soft, tough phase and the complex interfacial fracture behavior in such layered arrangements provide a myriad of possibilities for designed structural response. However, this combination of extremes in properties from phase-to-phase provides leads to difficulties in understanding mechanical response to a particular loading condition. We will present experimental approaches and supporting analysis to probe the following key physical processes in the generic sequence of deformation and fracture of layered brittle/tough microstructures:

1. stress development and first cracking of the ceramic;
2. multiple crack development and fragmentation;
3. polymer-ceramic debonding;
4. polymer rupture and energy dissipation.

We will use the example of laminated safety glass used in automotive windshields, security glazing and architectural safety glazing to demonstrate these stages of deformation for several loading conditions. Experiments are reduced to tests on model microstructures using simple loading configurations. Analysis draws heavily on computational methods. The use of cohesive elements implemented in finite elements to describe interfacial fracture (adhesion) and polymer-ligament energy dissipation will be described. The philosophy of materials design through combined model experiments and computational analysis will also be discussed.