An experimental method for quantifying tool–part shear interaction during composites processing

The success with which dimensional control during processing of composite structures can be modelled depends on the level of understanding of the underlying mechanisms that drive the accumulation of residual stresses in the part. Tool–part shear interaction during processing can cause substantial warpage in initially flat laminates, yet this phenomenon remains poorly understood. This paper presents an experimental technique in which a thin tool, instrumented with strain gauges, is used for characterizing the interfacial shear stresses that arise between the tool and part during processing. The results show that a sliding interface condition occurs during the majority of the cure cycle, although, at times the tool and part adhere together resulting in high interfacial shear stresses. This tool–part interaction occurs despite the use of a release agent, though the use of a fluoroethylenepropylene (FEP) release film at the tool–part interface reduces the effect.