The processing of polymer matrix composites requires the formation of an autohesive bond between the surfaces of adjacent polymer entities as well as with the fiber surface. This autohesive bond strength development in amorphous polymers has been extensively studied and modeled. This paper describes a study undertaken to describe the development of the autohesive bond between polymer surfaces in semi-crystalline matrix composites. The results show that the development of the autohesive bond competes with the formation of crystals and actually results in the decrease of fracture strength at long processing times.

No abstract

Powder impregnation technology is a relatively new fabrication method for polymer powder composites. A number of processes using this processing route have been developed. However, the transformation of these preimpregnated materials into fully densified composite structures has been performed empirically. A fundamental understanding of the process would therefore prove a good resource to the composite industry. The overall objective of this study was to develop a mathematical model that would describe the consolidation process. Experimental observations were used to categorize the process into three simple unit operations: heating, compression and cooling. Each of these stages was modeled independently. A one dimensional heat flow equation with appropriate boundary conditions was solved from the heating and cooling models. A three dimensional squeeze flow model with corresponding boundary conditions was used to describe the flow of the polymer in the lay-up. An existing fiber deformation model was used in order to predict the additional pressure required for consolidation. Data from experiments designed to test the heating and cooling model fit well with the simulations. Deviations from the model at short times were observed. However, the total heating and cooling times that were predicted were accurate. Experimental verification of the flow model showed that the time and pressure required for flow were extremely small compared to the fabrication cycle.

No abstract

No abstract