Surface optimization of continuous fiber reinforced thermoplastics
Continuous fibre-reinforced polymers (FRP), based on flat sheets, benefit from excellent weight-specific features. These include the possibility of load path optimised design and the option of functional integration. Consequently, FRP offer a high potential for lightweight design. Materials using thermoplastic-based polymers (so-called “organic-sheets”) allow fully automated and fast manufacturing based on their physical processing and are environmentally sustainable because of their recycling capability. Additionally, through improved optical and aesthetic characteristics, new applications can be developed for a mid to high scale production range.
However, commercial products exhibit a textile surface structure (so-called “fibre print through phenomena” – FPTP) and are therefore not very common for aesthetic applications. The FPTP always appears on the surface of organic-sheets and affects the appearance of the reinforcing architecture. The effect is determined by the non-uniform shrinkage behaviour of both composite partners inside the total system, which is further impacted by the different local volume fraction of the agents. As a result of the high thermal shrinkage behaviour of the matrix, sink marks are generated in high polymer regions while processing which hamper a glossy appearance of the surface.
The dependent temperature performance of the polymer matrix zone outside of the textile reinforcement can be adjusted to the properties of the impregnated fibres by adding fillers into the polymer resin before manufacturing. To adjust the polymer matrix zone locally, a filter effect of the fabric structure can be achieved by using suitable fibre and particle sizes. If the amount of polymer-filler-compound is calibrated optimally, the overall shrinkage behaviour of the resulting three-phase-composite can be homogenised and the viscous behaviour of the compound can be reduced. As a result, the surface quality of the FRP will be improved and its creep behaviour under changing temperatures will be reduced.