Investigating the Unrecovered Displacement of Glass Fibre Reinforced Polymers Due to Manufacturing Conditions

Abstract

In this industrial case study, the effect of processing conditions on the cure progression as well as the magnitude of creep strain due to storage/post-operations after de-moulding was investigated via a wet lay-up manufacturing of a glass fibre reinforced polymer (GFRP), commonly used in boat building. In addition, how the creep and the related permanent deformation in its recovery stage can be prevented or controlled was a focus of the study. Dynamic Mechanical Analysis (DMA) was used to monitor the creep rate of test samples while a constant stress was applied to mimic the sagging condition of GFRP parts during assembly stages. Differential Scanning Calorimetry (DSC) was used to determine the degree of cure as well as the glass transition temperature (Tg) at different curing temperatures. A direct relationship was found between the curing and the operating temperatures, and the unrecovered displacement seen in the final GFRP part. The unrecovered displacement was hypothesized to occur mainly due to a combination of cure progression and creep during the manufacturing process. Namely, cure progression results in the development of stiffness retaining the elastic deformation, while creep can create irreversible viscous flow. The results obtained may be particularly helpful to manufacturers of open moulded parts to prevent the costly consequence from excessive recurring of parts after de-moulding. doi:10.12783/issn. 2168-4286/2.2/Milani