Epoxy-based CFRP composites with induced single and multiple delaminations: flexural performance under four-point loading using digital image correlation

ABSTRACT

The present work explores the effect of induced single and multiple circular delamination(s) on both the strength and stiffness of carbon/epoxy composite laminate subjected to pure bending. The laminates consisted of stacking sequence [0/0/45/-45/90/45/-45/90]_S. They were manufactured using the hand layup method and vacuum bagging technique. The composites contained delamination(s) at the centre. The multiple delaminations have different sizes. They were inserted in a triangular pattern. Flexural tests were conducted in displacement control mode. The intact composite failed without delamination. The existence of multiple delaminations highly deteriorated the structural integrity and as a result the flexural properties decreased as compared to composites containing single delamination. Plies of the delaminated composite beams buckled locally on the compression side. Hence, the local out-of-plane displacement at the centre of the defect was measured using 3D DIC. The local out-of-plane displacement was higher in composites of induced multiple delaminations. Additionally, surface displacements and strains were measured at the region of interest. The causes of degradation in flexural performance and damages are also explained in detail.

KEYWORDS:

• Multiple delaminations
• Flexure
• local buckling
• out-of-plane displacement
• damage
• digital image correlation

Acknowledgements

The authors are grateful to Dr. Ramji Manoharan, Professor, Department of Mechanical and Aerospace Engineering, Indian Institute of Technology, Hyderabad, India for the permission given to work in the composites laboratory. The authors are also thankful to Dr. Gangadharan Raju, Associate Professor, Department of Mechanical and Aerospace Engineering, Indian Institute of Technology, Hyderabad, India for the suggestions given to carry out this work. They are grateful to Mr. Naresh Kolanu, Mr. Lala Bahadur Andraju, and Mr. M. Seshadri, Former Research Scholars, Department of Mechanical and Aerospace Engineering, Indian Institute of Technology, Hyderabad, India for the support given in the conduction of experiments.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The present research work has not been funded by any organization.