Schematic diagram of experimental setup Investigation of composites using optical coherence tomography Vishesh Dubey1, Vishal Srivastava3, Krishna Dalal2, Devjyoti Dalal2 and Dalip Singh Mehta1 1Department of Physics, Indian Institute of Technology Delhi, New Delhi- 110016, India. 2Department of Biophysics, All India Institute of Medical Sciences, New Delhi- 110029, India 3Department of Electronics and Communication Engineering, Amity University, Noida, India Introduction Schematic diagram of experimental setup Internal Structure (b) Volume reconstruction with high transparency (a) Reconstructed Volume of composite Fiber A Composite material is a material system composed of two or more macro constituents that differ in shape, size and chemical composition and insoluble in each other. There are two types of constituent materials: (i) MATRIX and (ii) REINFORCEMENT The wide application of composites requires to maintain the quality of the material The specification such as residual porosity, fiber architecture and structural integrity are important parameters of composites Study of cracks and imperfections inside the composites The defects inside the composite affect the strength of the material The cracks and deformities inside having a negative effect on the physical property of the material Importance So it is important to check the quality and quantity of the composite material and make sure to avoid the use of defected material Report: Optical method for the non-destructive, high resolution testing of the materials. Optical coherence tomography (OCT) is an emerging optical imaging technology that performs high-resolution, cross-sectional tomographic imaging of internal structure in biological systems and materials. OCT is a nondestructive and noncontact technique to image microstructure within scattering media. OCT performs imaging by measuring the echo time delay of reflected light using low -coherence interferometry The system is based on a Michelson type interferometer Fig.5: (a) Reconstructed volume of glass-fiber-reinforced epoxy composite material, (b) reconstructed volume with higher transparency Fig.3: Swept laser source (SS), fiber coupler (FC), polarization controller (PC), circulator (CIR), collimator (C), adjustable pinhole variable attenuator (AP), data acquisition board (DAQ) and mirror (M). In fig.5 (a) the glass-fibers are visible so that the imperfections in the matrix can be recognized In this volumetric image, the crack can be clearly seen along with other features of the composites As the transparency of the reconstructed volume is increases the internal structure can also be visible as shown in fig. (b). Methodology SS- OCT images of the composite material was captured. Using Computation method (MATLAB) the data was analyzed. By stacking multiple cross-sectional (en-face) images, volumetric reconstruction of composite material was made. As the transparency of the reconstructed volume is increases the internal structure can also be visible. Conclusion In fig.5 (a) and (b) the volumetric reconstruction of composite material is shown, by stacking multiple cross-sectional (en-face) images Using OCT internal features as well as quality of the material can be analyzed. Result and Discussion Opaque References Crack Opaque Crack W. Drexler, U. Morgner, F. X. Kartner, C. Pitris, S. A. Boppart, X. D. Li, E. P. Ippen, and J. G. Fugimoto,“Spectroscopic OCT,” Opt. Lett. 25, 111-113 (2000). (2) J. P. Dunkers, F. R. Phelan, D. P. Sanders, M. J. Everett, W. H. Green, D. L. Hunston, and R. S. Parnas, “The application of optical coherence tomography to problem in polymer matrix composites,” Opt Laser Eng. 35, 135-147 (2001). (3) J P Dunkers, R S Parnas, C G Zimba,R C Peterson, K M Flynn, J G Fujimoto and B E Bouma,“Optical coherence tomography of glass reinforced polymer composites,”Composites A 30,139–45 (1999). (4) S. Ramakrishna, J. Mayer, E. Wintermantel, K. W. Leong, “Biomedical applications of polymer-composite materials: a review,” Comp. Sci. and Tech.61, 1189-24 (2001). Crack Fig.4: OCT images of a glass-fiber-reinforced epoxy compound material, the cross-section images were taken perpendicular to the supporting glass-fiber structure at (a) 0.6 mm and (b) 0.8 mm depth. The arrows in the fig. 4 show the cracks imperfections in the composite material The circles in fig. 4 shows where the glass-fiber structure has not been penetrated properly by the epoxy resin Acknowledgement One of the author Vishesh Dubey is thankful to UGC (Ref.No.23/12/2012(ii)EU-V) New Delhi for financial assistance .