Fiber reinforced cement composites manufactured by extrusion technique have shown significant improvement in physical, mechanical ,and durable properties compared with the fiber reinforced cementitious composites made by traditional manufacturing techniques. As a result, they have a potential to be used in siding, backboard and paneling systems. For exterior wall application they must possess thermal insulation and even if possible thermal storage property .These properties could impart to the extruded composite by incorporating some materials whose thermal conductivity is low such as expanded perlite. Particulate paste, however, are quiet difficult to be extruded with smooth surface appearance of final extrudate due to arisen friction especially in die-land during extrusion process...[ Read more ]

Fiber reinforced cement composites manufactured by extrusion technique have shown significant improvement in physical, mechanical ,and durable properties compared with the fiber reinforced cementitious composites made by traditional manufacturing techniques. As a result, they have a potential to be used in siding, backboard and paneling systems. For exterior wall application they must possess thermal insulation and even if possible thermal storage property .These properties could impart to the extruded composite by incorporating some materials whose thermal conductivity is low such as expanded perlite. Particulate paste, however, are quiet difficult to be extruded with smooth surface appearance of final extrudate due to arisen friction especially in die-land during extrusion process.

This study, therefore, focuses on friction reduction in die-land by introducing an innovative method based on electro-osmosis flow induced in the die-land for friction mitigation.

The innovative introduced method forms a very thin layer of lubricant already present in the paste as liquid phase for friction reduction .

Regarding the research methodology applied in present study, first contact and friction in paste extrusion is investigated .Different friction models will be discussed .Then friction condition in die-land during ram extrusion is studied.

Second, formation mechanisms of surface defect is presented. What are the surface defect and how they form has been discussed. It has been established in this thesis that severe surface defects occurring inside the die-land are of surface pickup origin. To understand how they are formed, a microstructural study of the pickups have been performed. From these studies it was understood that formation of pickups is closely related to material transfer between the die-land and the extrudate surfaces, as a result of large adhesion between the counter-surfaces. A formation mechanism of surface pickups has been proposed.

Third, friction mitigation in die-land by electro-osmosis flow (EOF) has been studied. The results show that extrusion load reduces due to better wall slip as a result of EOF in die-land .Also in specimen panels manufactured by screw extruder, the surface roughness measured by a non-contact method called Vertical Scanning Interferometry (VSI) show reduction for those panels extruded by EOF even in case of panels contains expanded perlite particles

Finally, high performance fiber reinforced cement panels manufactured by extrusion using the newly developed EOF based lubrication method are introduced. The composites made from different raw materials has also thermal insulation behavior due to incorporated expanded perlite particles. The experimental results obtained in this thesis show that EOF is able to largely mitigate friction in die-land, help better wall slip of the paste and finally more smooth surface of particulate composite. The technique for friction mitigation has also potential to be applied in extrusion based 3D printing since during printing deposition rate will affect on properties of printed object/structure .So friction reduction to keep a constant rate of deposition during printing is very important .