Developing thermal energy-storing building materials is one of the effective ways to solve global energy and environmental problems we face. Incorporations of phase change materials (PCM) in building materials have been proved to be feasible to exploit high thermal storage capability of PCM to achieve the objective. In this study, short fiber reinforced cementitious panels incorporated with granular phase change composites have been manufactured by the extrusion technique which can significantly improve the mechanical performance of cement composites. In order to make extrusion process smooth and successful, rheological behaviors of fresh fiber reinforced cementitious composites need to be examined carefully....[ Read more ]

Developing thermal energy-storing building materials is one of the effective ways to solve global energy and environmental problems we face. Incorporations of phase change materials (PCM) in building materials have been proved to be feasible to exploit high thermal storage capability of PCM to achieve the objective. In this study, short fiber reinforced cementitious panels incorporated with granular phase change composites have been manufactured by the extrusion technique which can significantly improve the mechanical performance of cement composites. In order to make extrusion process smooth and successful, rheological behaviors of fresh fiber reinforced cementitious composites need to be examined carefully.

Firstly, rheological behaviors of fresh extrudate were investigated by utilizing upsetting or squeeze flow test throughout present study. Then a model containing both strain and strain rate was proposed to represent the stress strain relationships of fresh extrudate under different strain rates. The friction conditions were studied and friction factor was derived by using upper bound theory. Material parameters in the model were determined from experimental data. After that, the model was validated through Finite Element Method. Reasonable agreement between simulations and experimental results was achieved. Theoretical analysis of upsetting was further carried out in the interest of understanding the upsetting process better. A simple expression for the total force required to compress the specimen was developed. Agreement between this expression and experimentally measured force was good at strain values higher than elastic. In order to improve accuracy, an inverse problem was formulated with genetic algorithm to search accurate value of the parameters. During investigations process of rheological behaviors, digital image processing (DIP) technique was also used. Dimensions of deformed specimens which could provide useful information related to friction conditions were measured. And the displacements both at edges and contacting surface of specimen undergoing deformation were measured. Time dependent behaviors of fresh extrudate caused by chemical reactions and extrudability were assessed by stress relaxation and upsetting tests. A data interpretation method and generalized Maxwell model were used to interpret the stress relaxation process. At the same time, the influences of rheology modifier were addressed.

Secondly, productions of granular phase change composites and thermal energy-storing panels were presented. The thermal behaviors of extruded panels were investigated by one-dimensional heat conduction and simulated-room tests. It was shown that both heat capacity and thermal inertia were largely improved. The experimental results demonstrated that there could be a great potential for applying extruded thermal energy-storing panels in building constructions to improve energy efficiency.