The interface area of the face sheet and core of the sandwich composite is seen as a weakness due to its low de-bonding toughness. To overcome this concern, it is critical to develop a suitable modification strategy to enhance the de-bonding toughness of the face sheet/core interface. In the present study, the corrugated core reinforced sandwich composite was prepared through co-curing and secondary bonding approaches. The MWCNTs reinforced adhesive was induced in the face sheet/core interface in different weight concentrations. The MWCNT-reinforced adhesive was prepared using the sonication technique, and its dispersion was examined using atomic force microscopy (AFM). The three-point bending test revealed that sandwich composite prepared using the co-cure method has higher flexural strength than secondary bonded samples due to better bonding face sheet and corrugated core. Compared with MWCNT-free corrugated core reinforced co-cured sandwich composites (CCSC), the flexural strength of 1 wt.% MWWCNT-induced sandwich composite was increased by 101.28%. The microstructural study showed that secondary bonded samples had extensive fibre breakage at the face plate due to early de-bonding of the face sheet and corrugated core. Furthermore, the free vibrational analysis was performed to evaluate the natural frequency and damping values of the corrugated core reinforced sandwich composite. The modal test results indicated that inducing 1wt.% MWCNTs in the face sheet/core interface had enhanced the natural frequencies of co-cured sandwich composites. The present study provides a suitable method to address the weaker de-bonding toughness concerns of face sheet/core interface region of sandwich structures.

Evaluating the flexural and vibrational response of carbon nanotube strengthened co-cured sandwich composites
    Abstract
    1 Introduction
    2 Materials and methods
        2.1 Materials
        2.2 Synthesis of MWCNTepoxy adhesive
        2.3 Fabrication of secondary bonded corrugated core reinforced sandwich composite
        2.4 Fabrication of co-cured corrugated core reinforced sandwich composite
        2.5 Flexural analysis
        2.6 Free vibration analysis
        2.7 Microstructural analysis
    3 Results and discussion
        3.1 Flexural behaviour of corrugated core reinforced sandwich composites
        3.2 Free vibrational behaviour of corrugated core reinforced sandwich composites
    4 Conclusion
    Acknowledgements 
    References

• Thulasidhas Dhilipkumar(Department of Mechanical Engineering, Vinayaka Mission’s Kirupanada Variyar Engineering College, Vinayaka Mission’s Research Foundation (DU), Salem, Tamil Nadu 636308, India)
• Soundhar Arumugam(Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati, Assam, India)
• Murugan Rajesh(School of Mechanical Engineering, Vellore Institute of Technology, Vellore, Tamil Nadu 632014, India)
• Raja Venkatesan(School of Chemical Engineering, Yeungnam University, 280 Daehak‑Ro, Gyeongsan 38541, Republic of Korea) Corresponding author
• R. Sasikumar(Department of Mechanical Engineering, Vinayaka Mission’s Kirupanada Variyar Engineering College, Vinayaka Mission’s Research Foundation (DU), Salem, Tamil Nadu 636308, India)
• Bandar Ali Al‑Asbahi(Department of Physics and Astronomy, College of Science, King Saud University, P.O. Box 2455, 11451 Riyadh, Saudi Arabia)