Composites are currently being used in several applications including aerospace, marine, and automotive applications due to their high specific strength and stiffness, thermal and chemical stability, and the possibility to control the strength and stiffness properties by tailoring the fiber orientations. Thermoset matrix-based composites are the most common in current industrial applications. However, due to recycling constraints, thermoplastic-based composites are currently receiving more attention. Automated tape placement (ATP) is one of the processes used to manufacture fiber-reinforced composites FRC with a thermoplastic matrix. The process is computer controlled and is usually carried out in a clean room, which is in line with the requirements of modern manufacturing. The ATP process is accomplished by placing the tape accurately using the robot arm; at the same time, the laser melts, in-situ, the portion of the tape ready to be laid and a silicone consolidation roller applies pressure and cooling to finalize the process. The roller used in the current study was pressed onto the substrate by a pneumatic cylinder and cooled externally using compressed air to prevent the tape adhering to the roller during processing. The laser temperature used is higher than the melting temperature of the thermoplastic. Due to the multiple in-situ heating and cooling cycles, the composite parts manufactured with this process usually contain residual stresses which may affect the final cured specimen’s dimensional and geometrical accuracy, particularly for flat specimens. Hot-plate molding is generally used to reduce the thermally induced residual stress. In addition to the geometrical tolerance, the parts manufactured by this technique are expected to have more voids, as compared to the techniques used for the standard thermoset composites.

In the current paper, the aim is to assess the quality of the manufactured composites at the microscale level and compare with a thermoset composite. The parameters of interest are the void volume fraction, the distribution of the fibers within the matrix and the alignment of the individual fibers. Three materials were used for this study. Two thermoplastic matrix-based composites (IM7/PEEK and AS4/PA12) were manufactured using the standard ATP machine. For reference, IM7/8552 thermoset matrix-based composite was manufactured using prepreg with autoclave. After manufacture, the composite sheets were sliced into specimens for optical microscopy and computed tomography. The optical microscope was used to assess the distribution of the fibers inside the matrix whereas, the CT scans were used to assess void content and fiber alignment. The data were statistically treated after scanning. Compared to the well-established IM7/8552 composite, the micrography images reveal that the ATP results in higher volume of voids. On the other hand, ATP processing improves the alignment of the fibers, as the solidification process occurs while the fibers are in tension. For the distribution of the fibers, the images showed an area in between the different tapes with a smaller number of fibers, compared to the other areas. These results present a one step forward in understanding and improving the quality of the thermoplastic composites.


On the Manufacturing Defects of Thermoplastic Carbon/Epoxy Composites Manufactured by Automated Tape Placement

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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