Robotized Automated Fiber Placement and Automated Tape Laying (AFP/ATL) Processes for Composite Material Part Production

Automated fiber placement and automated tape laying (AFP/ATL) with laser assisted heating (LAFP/LATL) is an attractive manufacturing technology for the development of lightweight and high performance components, primarily for the aerospace, automotive, military and many other dominant industries worldwide. The products are commonly manufactured from a material called prepreg, which consists of carbon fibers impregnated with polymer resins. The process comprises the automated laying of fiber reinforced thermoplastic tapes to formation of a layer which merges with the previous one until the build up a final laminate structure. For the automated laying of the prepreg tape or fibers, a robotic installation is used for precise laying of the tape along predefined paths.
The investigation in the frame of this paper focuses on the in situ obtaining high performance composite parts based on thermoplastic prereg, without additional processing. For this purpose, the technological parameters of the process, the interlaminar bonding of the layers in the laminate structure as well as the properties of the prepreg materials and the obtained composite structure have been analyzed. This was done through a combination of experimental work mechanical analyses and with optical and scanning electronic microscopy (SEM) to study the microstructure of prepreg materials and laminates and their relationship to process parameters. For the investigation, two types of unidirectional prepreg materials based on carbon fibers and thermoplastic polymer matrices PPS and PEEK have been used. The laminate plates from the two types prepreg have been produced by ATL process and the influence of some technological parameters (processing temperature, laser placement angle and compacion pressure of the roller) have been determined. For all produced specimens, the flexural strength have been tested. For all two types of laminate plates, it has been found that the processing temperature and the compaction pressure of the roller significantly influence on the flexural strength of the laminate plates. The change of the processing conditions makes a change in the mechanical characteristics of the laminate plates, as a result of a well achieved interlaminar bonding between the layers in the laminate. Namely, the samples obtained at the highest investigated processing temperatures and compact roller pressure have the highest values for flexural strength. Microscopic analysis of the samples with the highest values of flexural strength have shown a good interlaminar bonding between the layers and a small percentage of pores compared to the samples with the lowest values of flexural strength where the pore content is higher.

Key words: thermoplastic prepreg, automated fiber placement, automated tape laying, interlaminated bonding, compression molding, optical and scanning microscopy.