Non-Isothermal Autohesion Model for Amorphous Thermoplastic Composites

Abstract

Two-dimensional heat transfer analyses for non-isothermal molding of amorphous thermoplastic polymers and composites are presented. Solutions of the heat transfer analyses were obtained using the finite element technique, which includes convec tive heat transfer from the boundaries of the specimens. A non-isothermal autohesion model was developed by coupling the heat transfer analyses with an isothermal autohesion model for Udel P1700 polysulfone. The resulting computer code allows prediction of the time required for crack healing in amorphous polymers and autohesive bonding of the ply interfaces of fiber-reinforced composites under non-isothermal processing conditions. Results of the model are compared with data obtained during crack healing of Udel P1700 compact tension specimens and compression molding of 64-ply graphite/polysulfone com posites. Agreement between the model and data was good.

Adhesion of high performance thermoplastic composites: Development of a bench and procedure for kinetics identification

“…This is a classical approach used in the modelling of several manufacturing processes, such as press forming or compression moulding [16,26], tape placement processes [6,7] or welding [27].…”

A combined optical-thermal model for near-infrared laser heating of thermoplastic composites in an automated tape placement process

“…The melted surfaces are pressed together as they pass under the consolidation roller, forming a bond. The fundamental mechanism of strength development is the inter-diffusion of polymer molecules at the bond interface, a highly temperature dependent process known as healing or autohesion [2,3]. When two surfaces are brought together, the contact is limited to asperities.…”

Understanding Joint Formation in Thermoset Composite Welding (TCW) Joints

“…welding. It should also be noted that if the temperature distribution over an interface is not even, some portions of the interface may be better healed than others, leading to an uneven strength distribution [117]. For example, the formation of intimate contact is generally the rate controlling step for filament winding processes as the time over which pressure is applied to a specific point is very short in comparison to the TCW welding cycle.…”

“…of the interface using methods such as ultrasonic pulse echo to determine the degree of healing of the interface. [131]2.7.1 Fracture TestsFracture tests have been used in literature to determine the fracture toughness ( ) and the critical strain energy release rate ( ) of an interface[117, 118, 122,124,[144][145][146]. The fracture toughness of the interface is measured by initiating a crack in a specimen with either a thin insert or a crack created prior to or after welding with length, .…”

“…The two mechanisms that control the bonding xiii of the welded interface are: intimate contact, elastic and plastic deformation of surface asperities, and healing (or autohesion), diffusion of polymer chains at the interface. This section of the literature review covers these two mechanisms that occur during the welding of two thermoplastic surfaces together [26, 48, 49].Equation 2.13 shows that the degree of bonding for a thermoplastic interface is a factor of the degree of intimate contact and the degree of healing[117, 118]:…”