72 A. Tessema et al. interface. The interfaces in our laminate are made of 0ı, 90ı, C45ı and 45ı plies, and the 0ı ply has the highest shear modulus, the C45ı and 45ı plies follows and the 90ı ply has the least. Therefore, the ˙45/0, C45/ 45, ˙45/90 and 90/90 interfaces have higher the stiffness accordingly. The other factor for the shear localisation at the interface is the relative axial and shear displacement between two adjacent plies. Variation in the axial/shear displacement occurs when the two plies have different properties or fiber orientation, and this variation induces shear lagging between the two plies. Under a given axial tension load, the ˙45 plies have the highest inplane shear strain. The inplane shear strains developed in the C45ı and 45ı plies have opposite orientations. As a result a higher shear strain localisation is expected at the interface of C45/ 45, ˙45/90and ˙45/0 plies accordingly. The combined effect of interface stiffness and interface shear lag produces the shear strain localisations at the interfaces. The shear strain localizations obtained at each interface from this study matches the above explanation. 9.5 Summary Uniaxial tension test is performed on three quasi-isotropic laminates with different ply arrangements. Using Digital Image Correlation (DIC) the full-filed strain across the thickness of the laminate at the free-edge of the tests coupon is captured at a different stage of loading. From the experiments, it is obtained that matrix cracking is the primary and dominant form of damage and it usually occurred in the 90ı-plies. However, the orientation and quantity of matrix cracks are highly affected by the stacking arrangement of the plies. Further, shear strain localizations have been observed in most of the interfaces and the highest shear strain are obtained at the C45/ 45 interfaces. References 1. Tong, J., Guild, F.J., Ogin, S.L., Smith, P.A.: On matrix crack growth in quasi-isotropic laminates—I. Experimental investigation. Compos. Sci. Technol. 57, 1527–1535 (1997) 2. Tessema, A., Mymers, N., Patel, R., Ravindran, S., Kidane, A.: Experimental investigation on the correlation between damage and thermal conductivity of CFRP. In: Proceedings of the American Society for Composites: Thirty-First Technical Conference, Williamsburg (2016) 3. Tessema, A., Ravindran, S., Kidane, A.: Experimental study of residual plastic strain and damages development in carbon fiber composite. Fract. Fatigue Fail. Damage Evol. 8, 31–36 (2017). Springer 4. Shelke, A., Uddin, A., Yang, J.: Impact identification in sandwich structures using solitary wave-supporting granular crystal sensors. AIAA J. 52, 2283–2290 (2014) 5. Berthelot, J.: Transverse cracking and delamination in cross-ply glass-fiber and carbon-fiber reinforced plastic laminates: static and fatigue loading. Appl. Mech. Rev. 56, 111–147 (2016) 6. Mittelstedt, C., Becker, W.: Interlaminar stress concentrations in layered structures: Part I – a selective literature survey on the free-edge effect since 1967. J. Compos. Mater. 38, 1037–1062 (2004) 7. Crossman, F.W., Warren, W.J.: Initiation and growth of transverse cracks and edge delamination in composite laminates Part 2. Experimental correlation. J. Compos. Mater. Suppl. 14, 88–108 (1980) 8. Amrutharaj, G.S., Lam, K.Y., Cotterell, B.: Delaminations at the free edge of a composite laminate. Compos. Part B Eng. 27, 475–483 (1996) 9. Joo, J.W.W., Sun, C.T.T.: A failure criterion for laminates governed by free edge interlaminar shear-stress. J. Compos. Mater. 26, 1510–1522 (1992) 10. Pagano, J., Pipes, R.B.: The influence of stacking sequence laminate strength. J. Compos. Mater. 5, 50–57 (2016) 11. Alton Highsmith, K.R.: Stiffness-reduction mechanisms in composite laminates- damage in composite materials: basic mechanisms, accumulation, tolerance, and characterization. ASTM STP. 775, 103–117 (1982) 12. Tessema, A., Mitchell, W., Koohbor, B., Ravindran, S., Kidane, A., Van Tooren, M.: On the mechanical response of polymer fiber composites reinforced with nanoparticles. Mech. Compos. Multi-funct. Mater. 7, 125–130 (2016). Springer 13. Ogihara, S., Takeda, N., Kobayashi, S., Kobayashi, A.: Effects of stacking sequence on microscopic fatigue damage development in quasiisotropic CFRP laminates with interlaminar-toughened layers. Compos. Sci. Technol. 59, 1387–1398 (1999) 14. Tessema, A., Mitchell,W., Koohbor, B., Ravindra, S., Kidane, A., Van Tooren, M.: Effects of nanoparticles on the shear properties of polymer composites. In: American Society of Composite Technical Conference (2015), Mesa Costa, California
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