Development of intimate contact during processing of carbon fiber reinforced Polyamide-6 tapes

Contact development between the surfaces of two tapes is considered as a critical step in processing carbon fiber reinforced thermoplastic composites. In this study, the development of intimate contact between carbon fiber reinforced Polyamide-6 (PA-6) tapes is investigated experimentally using consolidation experiments and X-ray computed tomography for quantitative contact characterization. The experimental results indicate that the development of intimate contact occurs in the range of seconds even when temperatures are only slightly above the melting temperature and applied pressures is in the range of 1-4 kPa. Experimental data are compared with the results of the two analytical models proposed by Lee and Springer as well as Yang and Pitchumani. Both models overestimate the time needed to reach full contact for the PA-6 tape. In comparison to previously investigated PEEK materials, PA-6 has a relatively low viscosity and the tapes possess a resin-rich layer near the surface, which seems to influence the contact development process. Besides the assumptions made for viscosity, the sensitivity to input parameters describing the surface topology strongly influence the model results and the accuracy of predictions. </jats:p

Quantification of local fiber distribution for optimization of tape laying techniques

An image processing routine is proposed to quantify distribution of fibers on different length scales in unidirectional fiber reinforced composites. For this purpose the proposed image analysis is validated utilizing artificial images and subsequently demonstrated in application to micrographs of carbon fiber reinforced Polyamid-6 tapes and corresponding laminates fabricated by automated tape laying. We use 2D-mean filters with varying diameter to systematically reduce the image information to the characteristic length scale and to obtain the respective local fiber volume fraction. The results indicate a correlation between the microstructure of the tapes and the distribution of fibers within the corresponding laminate