Abstract

The competitive advantage of an automated, true out-of-autoclave composite
manufacturing process is realized. Decades of research has been directed toward enhancing
technologies and processes such as the automated fiber placement AFP of carbon fiber
reinforced thermoplastic CFRTP composite materials. One of the latest technological
advancement in the AFP process is the introduction of continuous-wave high power fiber lasers.
Together with the development of thermoplastic material systems, it is now possible to in-situ
consolidate parts at efficient rates with promising quality. A ring manufacturing setup capable of
in-situ consolidation of thermoplastic composite tape is developed for the following study. A set
of collimating focusing and beam shaping lens are used to transform a Gaussian beam of a high
power continuous-wave fiber laser to a square, top-hatted beam, with uniform intensity profile at
the desired working distance. 20-Ply CFRTP PEEK rings, 152 mm in diameter, are manufactured
for the experimental studies. Design of Experiments using Taguchi approach is employed to
investigate the effect of major process parameters on the mechanical properties of the rings.
Effect of placement rate, laser power, and compaction force is evaluated against ILSS of samples.
Influence of parameters and a near-optimum point within the processing window is obtained.
Compaction force beyond a certain limit is deemed to have the least impact amongst others on
ILSS. An optimum set of parameters are then used to produce rings at a 50% higher placement
rate compared to those made using hot-gas-torch process. To investigate further increase in
placement rates variation of ILSS with laser power is studied for up to 152 mm/s. A decline in
ILSS is observed with the increase in placement rate as the degree of intimate contact
diminutions. The use of a conformable roller, with transparent to NIR light material, sufficient
hardness, and internal cooling is necessary to maintain the degree of intimate contact at higher
placement rates. To enhance the degree of autohesion a larger rectangular spot size could be used.
However, it is shown that the thermal efficiency decreases as the spot size widens away from the
nip point. Finally, the measurement of temperature at nip point suggests that the bonding of up to
two preceding layers may be affected at each pass and that to keep a constant nip point
temperature for the winding-like manufacturing process the laser power shall vary.