No abstract

Objective of this study is to present new developments in thermo-plastic pultrusion (a pullbraiding process combined with a contact preheating system, and a new online forming method for pultruded profiles) and a new approach for modelling of the preheating process. After modelling of the preheating process of commingled glass fibre/polypropylene yarn, the preheating of a thermoplastic pultrusion line to produce profiles with unidirectional reinforcement in axial direction was modified by adding contact heating pins. Compared to the convective heating used before, profiles with higher qualities could be produced at three times higher processing speeds. First trials of a combined braiding and pultrusion process, also with contact preheating, led to promising results. Furthermore, a process to post-form pultruded profiles immediately after leaving the heated pultrusion die was developed, leading to profiles with a forming radiusof 10 cm.

The present study reports about the pultrusion of a carbon fiberreinforced PA12 yarn containing discontinuous carbon and polyamide fibers. This is the first attempt to pultrude this material. Rectangular cross sectional profiles have been successfully produced using a self-designed pultrusion line. In a series of experiments, the pultrusion parameters, such as preheating method, die temperature, and especially the pulling speed, which represents a determining factor regarding a potential industrial application, are varied.A complete characterization of each profile is conducted to examine the influence of processing parameters on the profile quality. The mechanical properties are evaluated by performing three-point bending as well as shear tests. The void content is also determined. The pulling speed seems to have the greatest influence on the profile quality. Under certain conditions of speed and temperature, the pultruded profiles exhibit good mechanical performance and a void content below 2%. The shear strength reacts most sensitively to the process parameter variations and can be used as a quality criteria.KEY WORDS: thermoplastic pultrusion, carbon fiber-polyamide 12 yarn.

The effect of electron beam (EB) radiation on carbon fibre reinforced (CF) thermoplastic (PBT, PPS, PA) composites was investigated. To clarify whether crosslinking could take place without or only with the presence of a crosslinking agent, special attention was paid to the incorporation of this agent into polymer sheets with a carbon fibre content of 50% by volume. The thermal and mechanical properties of the materials before and after exposure under different irradiation doses were evaluated. For materials based on PBT, PPS and PA46, no significant changes in properties after irradiation could be observed. However, CF/PA66 exhibited some changes in the presence of a crosslinking agent after irradiation, which could be related to an irradiation-induced crosslinking reaction. The effect of irradiation on the flexural properties was insignificant but an improvement in the creep behaviour was observed. Non-reinforced PA66 plates were also manufactured and a gel content measurement indicated that crosslinking was successfully induced. Additional studies allowed the changes in the polymer due to this crosslink to be quantified.