Sub-project A02 focuses on the manufacturing of unidirectional (UD) fibre-reinforced, functionally graded laminates using UD-reinforced, graded UD-reinforced and non-reinforced, monolithic thermoplastic tape materials. The laminates serve as a base structure for the Elementary Flat Structure (EFS) demonstrators manufactured in sub-projects A03 and A04. UD-tapes with different fibre volume contents, purely thermoplastic tapes without fibre-reinforcement and pre-graded UD-tapes from sub-project B05 are employed and combined to create novel, tailored, graded laminates. A02 analyses the processability of these materials to realise defined gradings as well as the interdependencies between the various process parameters, materials, and resulting properties. The SP Phase I uses carbon fibre-reinforced tapes due to the extensive existing research in literature and from previous research projects at AZL using this material. The process of automated tape placement originates from the aerospace industry, where carbon fibres are researched in depth.
Investigations span from machine components for processing graded and unreinforced tapes, process parameter windows and the influence of historical process data, to detailed material models including optical
and thermal properties for laser-assisted tape placement of these materials with in-situ consolidation.
The processability of the different tape materials is enabled through technological innovations and advanced process and material models. Therefore, novel machine components to process non-reinforced, monolithic thermoplastic tapes and graded tapes are researched and integrated. The main challenge here is the application of material tension as well as cutting and adding material during operation, which is necessary for highly productive manufacturing. Subsequently, the interdependencies of layup plan and ply-book, processing parameter levels, and resulting grading in the laminate are researched in depth. The resulting grading can be defined by parameters such as volumetric fibre distribution, thickness fibre distribution or fibre bundle homogeneity. Expected influences are the visco-rheological properties of differently reinforced materials, the temperature level, thermal distribution, thermal history, pressure distribution, material tensioning force, and layup sequence, i.e. the substrate material.
On a microstructural level, the fibre distribution and fibre volume content gradients are analysed using microscopic analysis of laminate cross-sections. Void content in the interlaminar layers is determined and a process-structure-property relationship for high-quality manufacturing of graded laminates is established. On a macroscopic level, the graded laminates are analysed in regard to bending stiffness, bending strength, maximum elongation at break, and peel strength.
Detailed analytical and numerical material models for optical absorption and thermal distribution resulting from laser-assisted tape placement of graded laminates are researched. Existing models for conventional UD-tapes are extended with thickness-dependent morphological, thermal, and optical properties.
Process planning and machine configuration constitutes an additional, major research focus. Manufacturing graded laminates adds a further dimension to part design and manufacturing. The innovative automated tape placement machine from AZL, the “Ultra-Fast Consolidator” is a highly modular system with the possibility to include multiple, different material batches. It additionally has the potential for manufacturing high lot sizes in short cycle times down to 5 seconds per laminate. The exponentially increasing complexity due to manufacturing high volumes of different variants using different, partially graded materials requires in-depth research for adaptive manufacturing planning and optimised machine configuration.
Finally, this sub-project integrates sensor and machine data during manufacturing in a global data ecosystem in collaboration with SP C06. A02 integrates relevant quality and process data from graded tape manufacturing (SP B05), further processing of graded laminates through pressing and injection moulding (SP A03, A04), and lastly from part quality control (SP B01). Sub-project A02 researches algorithms for controlling processing and process parameters to fulfil quality criteria of the final part in dependence on process parameters from tape manufacturing and part forming.