## 3 Experimental Results  
Depending on the winding speed, different results were obtained in terms of composite aesthetics, thickness and mechanical performances. Figure 5a shows the appearance of a typical consolidated composite (at the winding speed of 18 deg/s). All the consolidated composites showed a good adhesion of the prepreg tape along its revolutions. Evidently, the adopted process conditions (_i.e.,_ the low laser power, the focalization condition) were sufficient to cause the polypropylene to melt, and the applied force was sufficient to produce the matrix flow necessary for the consolidation. In particular, a very low consolidation force (on average 1 N) was used in combination with a very low laser power (50 W). Low laser power values are generally applied when a good radiation absorption is exhibited by the processed materials. In this case, not only the prepreg but also the underlying steel tube cooperate for the success of the laser-assisted forming operation. The efficiency of the consolidation phase is clearly shown by the mechanical tests. Figure 5b shows a composite sample during compression: A high deformation is applied to the sample without observing any delamination or break. Quantitative results are shown in Figure 6a and 6b in terms of compression curves. Figure 6a shows the dependence of the mechanical performance of the composite samples on the winding speed. In a previous study, the authors already discussed the results of compression tests on thin composite tubes which were produced by molding the same PP prepregs used in the current study [11]. Even if longer tubes were formed, a similar mechanical behavior was observed. By increasing the winding speed, the compression curve decreases. In all the cases, sample breakage was never observed because of the ductile behavior of the thermoplastic matrix composite. However, more reliable results were observed at the highest value of the winding speed: Figure 6b shows the comparison between two composite samples processed at 18 deg/s. Even if the overall reliability has to be improved, at lower winding  
Figure 5: (a) Wound composite at the end of the consolidation process and (b) during compression. speed much lower reliabilities were observed. The material degradation was always avoided, but at lower winding speed the input energy increased and the excess in the material flow made the control of the consolidation process impossible. At high energy inputs, the polymer viscosity is so low that the friction force of the tensioner generates a strong interpenetration of the adjacent layers. Probably the best way to consolidate the prepreg tape is to form the material in a semisolid state: the PP matrix has to be soft enough to make the layer joining possible, but not so much to squeeze away from the consolidated layers. This statement is confirmed by Figure 7a and 7b, where the final thickness of the composite samples and the appearance of a composite sample processed at 16.2 deg/s are shown, respectively. Unfortunately, a high thickness variation was observed in the composite rings: a similar variation was also observed along the circumference of each single ring. By increasing the winding speed, the composite thickness increases because of the lower interpenetration between adjacent layers. As the prepreg tape was 0.35 mm thick and 6 revolutions were performed, a maximum composite thickness of 2.1 mm would be expected in the case of a perfect joining between adjacent layers without interpenetration. However, due to the lack of uniformity of the provided tape, the non perfect circular shape of the first tape revolution, and the tape continuity, an average thickness about 2.6 mm was measured in the case of the composite sample processed at 18 deg/s. In this case, the structure of the superimposed layers was still visible through the thickness of the consolidated sample. By decreasing the winding speed, the layer interpenetration increases and the thickness decreases.