Optical coherence tomography image analysis of polymer surface layers in sound-absorbing fibrous composite materials

The material surface layer affecting sound absorption was identified by optical coherence tomography (OCT) image analysis. To characterise this layer, a special algorithm was developed to distinguish the polymer surface layer in thermoplastic composite materials, define its structure and thickness, and specify differences in these properties. The composite materials were obtained by thermal pressing of multilayer systems comprising viscose/polylactide and polylactide nonwoven fabrics, yielding thin polymer surface layers on the order of several hundred micrometres. The results of the measured sound absorption coefficient were analysed together with the OCT results. The use of OCT for the study of materials with specific acoustic characteristics was successfully demonstrated.