A study on Automated Fiber Placement of LM-PAEK using direct electrical resistance heating
Topic(s) : Manufacturing
Co-authors :
Yannis GROHMANN (GERMANY), Jonas VON HEUSINGER (GERMANY), Daniel STEFANIAKAbstract :
Within the research field of Automated Fiber Placement (AFP), the layup of thermoplastic tapes has emerged as a focal point in recent years. The state-of-the-art heating technology for this process comprises predominantly lasers. One of the goals using that technology is to achieve good part performance with minimal process complexity through the in-situ layup process, which has proven challenging. Difficulties arise from quality issues associated with complex part geometries and the inherently slow process speeds.
A promising highly productive alternative is introduced. The utilization of direct electrical resistance heating of the carbon fiber (cf) tapes during the layup process enables layup speeds exceeding 2 m/s. The basic principle of this technology is intrinsically heating the electrically conductive carbon fibre tapes directly in front of the consolidation roller. However, using layup speeds well above 1 m/s within the AFP process and only heating the tape that is fed during the process, reduces the layer adhesion. Nevertheless, the significant increase in layup speed allows for a post-consolidation of the preform, which is mandatory to ensure a good layer adhesion and furthermore can improve mechanical part performance in comparison to the in-situ process.
Nevertheless, using direct electrical resistance heating for the AFP process is a relatively recent approach and the technology is still undergoing development. Despite demonstrating promise in dry fiber placement processes, its advantages in heating thermoplastic carbon fiber prepregs have yet to be proven. The electrically isolating matrix complicates achieving a homogeneous temperature distribution within the tape when using the Joule effect, raising concerns about hot spots which could potentially damage the matrix.
This study investigates the layup of LM-PAEK laminates using an AFP prototype head that is equipped with the Continuous Resistance Heating Technology (CoRe HeaT). First layup trials are evaluated using wedge peel and single-lap shear test specimens. Furthermore, single tape tensile tests and micrograph samples help to understand the effects of different process parameters on the tape material. After improving the process parameters based on the results of the preliminary tests, a set of test laminates are produced. After the layup process, the laminates are post consolidated in a hot press. A reference laminate is manufactured using hand laid prepreg sheets of the same material, using the same post consolidation process. For the final evaluation, the test laminates are compared to the reference laminate using ILSS tests (DIN EN ISO 14130), 0° tensile tests (DIN EN 2562) and 90° tensile tests (DIN EN ISO 527-5).
A promising highly productive alternative is introduced. The utilization of direct electrical resistance heating of the carbon fiber (cf) tapes during the layup process enables layup speeds exceeding 2 m/s. The basic principle of this technology is intrinsically heating the electrically conductive carbon fibre tapes directly in front of the consolidation roller. However, using layup speeds well above 1 m/s within the AFP process and only heating the tape that is fed during the process, reduces the layer adhesion. Nevertheless, the significant increase in layup speed allows for a post-consolidation of the preform, which is mandatory to ensure a good layer adhesion and furthermore can improve mechanical part performance in comparison to the in-situ process.
Nevertheless, using direct electrical resistance heating for the AFP process is a relatively recent approach and the technology is still undergoing development. Despite demonstrating promise in dry fiber placement processes, its advantages in heating thermoplastic carbon fiber prepregs have yet to be proven. The electrically isolating matrix complicates achieving a homogeneous temperature distribution within the tape when using the Joule effect, raising concerns about hot spots which could potentially damage the matrix.
This study investigates the layup of LM-PAEK laminates using an AFP prototype head that is equipped with the Continuous Resistance Heating Technology (CoRe HeaT). First layup trials are evaluated using wedge peel and single-lap shear test specimens. Furthermore, single tape tensile tests and micrograph samples help to understand the effects of different process parameters on the tape material. After improving the process parameters based on the results of the preliminary tests, a set of test laminates are produced. After the layup process, the laminates are post consolidated in a hot press. A reference laminate is manufactured using hand laid prepreg sheets of the same material, using the same post consolidation process. For the final evaluation, the test laminates are compared to the reference laminate using ILSS tests (DIN EN ISO 14130), 0° tensile tests (DIN EN 2562) and 90° tensile tests (DIN EN ISO 527-5).