Fabrication of Functionally Graded Porous Polymer Structures using Thermal Bonding Lamination Techniques

Functionally graded porous materials (FGPMs) are porous structures with porosity gradient distributed over volume. They have many potential applications in aerospace, biomedical, and other industries. Despite significant efforts have been made to fabricate FGPMs, the existing manufacturing techniques are either complex, expensive, unable to control exact porosity distribution, or unable to create closed cell structures. This paper presents an additive approach for fabrication of polymer FGPMs with both closed cell and open cell structures using thermal-bonding lamination techniques. Under applied compressive load, controlled heating, and appropriate holding time, it was shown that this thermally induced bonding technique can bond layers of polymer sheets to create porous three-dimensional objects. The effects of various factors on the bonding shear strength were investigated. It was found that the bonding strength can be controlled by properly setting the pressure, temperature, and time in the process. The fabricated FGPMs specimens with different porosity configurations were further characterized using compression test in the normal and transverse directions. The results show that the developed techniques can be used to obtain FGPMs with various effective moduli.