Thermoplastic Composite Research Center (TPRC) members Remco Akkerman, Mark Bouwman and Sebastiaan Wijskamp co-authored an article titled Analysis of the Thermoplastic Composite Overmolding Process: Interface Strength, which has been published in Frontiers in Materials.
Thermoplastic Composite Research Center
TPRC over-moulding research paper published
Forming induced deconsolidation and remaining sink holes after overmolding the C/PAEK grid stiffened curved panels
The researchers analysed the over-moulding process of thermoplastic composites and studied the bond strength between the over-moulded composite laminate and the injected polymer resin by means of process modelling and mechanical testing. Their evaluation of both a single step and a dual step process led to distinctly different process mechanisms and resulting material structure, as well as mechanical performance of the parts.
Over-moulding, as defined by the TPRC, is a technology in which a thermoplastic composite laminate is thermoformed and injection over-moulded. This manufacturing process is suited for automated large-series production of complex 3D structures with excellent structural performance and a high level of function integration.
There is a need, however, for process design tools, which are currently lacking. For this purpose, the bond strength between the over-moulded composite laminate and the injected polymer resin was studied.
Starting from De Gennes' classical reptation theory for reptation and healing of amorphous polymers, an alternative approach was developed to describe the strength development for semi-crystalline materials. A rudimentary description of the degree of melting was implemented to predict the bond strength as a function of the thermo-mechanical history at the interface during forming and subsequent resin injection for PA6 and PEEK.
Dedicated coupon geometries were developed, manufactured and tested to evaluate the bond strength under tensile and shear loading conditions. Suggestions are presented for optimum process conditions and improved design features to further mature this technology.
Based in Enschede, the Netherlands, the TPRC performs high-end research in the field of thermoplastic composites. A list of all publications and PhD theses can be found on its dedicated publications website.