Overmoulding of Consolidated Fibre-Reinforced Thermoplastics - Increasing the Bonding Strength by Physical Surface Pre-Treatments

Fibre-reinforced thermoplastic materials enable an automated and economical manufacturing of lightweight structures in series-production. By combining different material-configurations, highly stressable components can be designed. Previous studies have shown that the combination of continuous fibre-reinforced hollow profiles and injection moulding compounds is suitable even for crash-relevant automotive parts. During the overmoulding process, the pre-consolidated hollow profile must remain cold in order to withstand high injection pressures. However, this leads to a poor adhesion between the profile and the overmoulding material. To increase the bonding strength, the interface can be pre-treated using laser and plasma technology. In this work, fibre-laser and atmospheric pressure plasma treatment are applied to glass fibre reinforced polyamide 6 composite (PA6/GF) sheets. The resulting surface properties are investigated by wettability and microscopy analysis. Afterwards, single-lap-shear specimens and special rib specimens are manufactured by overmoulding the sheets with PA6-66/GF bulk material. The resulting bonding strengths are characterised in tensile shear tests as well as pull-off tests of the ribs. The effects of different pre-treatment parameters on the bonding strength are analysed. Additionally, the effect of sheet temperature on the bonding strength is investigated, also including specimens without pre-treatment. Finally, the results are discussed with regard to the surface treatment of composite hollow profiles, considering bonding strength, manufacturing environment and processing times. (C) 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the 2nd CIRP Conference on Composite Material Parts Manufacturing.