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