Manufacturing Process Models for Thermoplastic Composites

Abstract

Models were developed which simulate the processing of thermoplastic matrix composites. The models relate the applied temperature, pressure, speed, and time to the temperature, crystallinity, consolidation, interlaminar bonding, and residual stresses and strains inside the composite. The formulations follow the models proposed by Springer, Loos, and their coworkers for manufacturing plates in a press or in an autoclave, but were extended to include cylindrical geometries, variations in the applied temperatures and pressures with position and time, and rapid bonding. These extensions make the models applicable to the manufacture of plates by tape laying and to filament winding of cylinders. These models were incorporated into a user friendly computer code which can be used to generate numerical results and to select the appropriate processing conditions for processing thermoplastic composite plates 1) in an autoclave, 2) in a press, or 3) by tape laying, and 4) for filament winding thermoplastic composite cylinders.

Simulation of the Tape‐Laying Process for Thermoplastic Matrix Composites

“…Several models [10][11][12][13][14] were developed to study the intimate contact problem. It was first described by Dara and Loos, 10 assuming that the surface asperities are flattened through shear flow.…”

“…It is the only dependency of the viscosity that is currently considered for the simulation of the tape placement process. [12][13][14]18 Polymeric melts show a non-Newtonian flow behavior, which means that the shear stress is not proportional to the shear rate. In most cases, they show a shear thinning behavior, which means that when the shear rate reaches a certain value the viscosity starts to decrease with increasing of the shear rate.…”

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

“…When two surfaces are brought together, the contact is limited to asperities. Sufficient temperature and pressure application allows the surfaces to deform into one another, a process known as intimate contact development [4,5]. Autohesion can only occur in regions of intimate contact, therefore the bond strength development process is a combination of both phenomena.…”

An inverse model for optimisation of laser heat flux distributions in an automated laser tape placement process for carbon-fibre/PEEK

“…The consolidation roller then presses the molten surfaces together as they cool, resulting in a bond. The bonding process is a combination of the flattening of the asperities at the interface (intimate contact development [11][12][13]), and the diffusion of polymer chains across the interface (autohesion or healing [14][15][16]). Other physical processes occur simultaneously during the process such as changes in crystallinity [5,17,18], void content [9,19], residual stress [20,21] and degradation [22,23] -all of which are sensitive to the specific temperature history.…”