Advanced 3D and 2D damage assessment of low velocity impact response of glass and Kevlar fiber reinforced epoxy hybrid composites

Abstract

This work focuses on quasi-static mechanical (tensile, flexural, indentation), low velocity impact (LVI) and viscoelastic behaviour of different stacking sequences and ] of 16 layers woven roving Kevlar-E-glass/epoxy interply hybrid composites. The outermost layers are Kevlar and remaining 14 E-glass layers are placed as interior for making these hybrid laminates. The viscoelastic properties are measured over the temperature range from 25 °C (room temperature) to 180 °C at three different frequencies (1, 10 and 50 Hz) by using the dynamic mechanical analyzer (DMA). The LVI results indicated that Kevlar-glass/epoxy hybrid laminates exhibit the highest damage threshold load (DTL) whereas laminates possess the higher peak load and threshold and maximum energies. Advanced non-destructive testing techniques (NDT) such as X-ray computed tomography (X-CT) and ultrasonic C-scan are employed to evaluate the micro and macro damage mechanisms of LVI tested specimens, respectively. Detailed observations have been made on the onset and growth of cracks in 30°, 45° and 0° plies using X-CT scan imaging. These images show that the bottommost plies subjected to more impact than the topmost plies, the outer Kevlar plies protect the inner 0° glass plies and delays the delamination propagation. ‘C’ scan images indicate that laminates spread the damage to more area. The scanning electron microscopy (SEM) is used for examining the failure mechanisms of indentation specimens.

Keywords:

• Stacking sequence
• hybridization
• damage threshold load
• non-destructive testing
• activation energy

Acknowledgement

The authors are grateful to Prof. Krishnan Balasubramanian, MDS, IIT Madras for his valuable support and allowing us to perform NDT (‘X-CT’ scan and ‘C’ scan).