Abstract
The primary objective of this work is to demonstrate how the condition for biaxially loaded off-axis tunnelling crack growth can be reproduced in a modified laminate under uniaxial loading. More specifically, laminates with the stacking sequences [0/θ/0/-θ] s and [0/α/0/-α] s have been considered for the biaxial and uniaxial loadings, respectively. A steady-state crack growth condition is analysed for an isolated off-axis tunnelling crack. The crack tip stress state is expressed in terms of a through thickness averaged mode mixity and energy release rate. The presented framework uses an energy accounting method with the crack opening displacements extracted from a finite element analysis. Results shows that the tunnelling crack tip stress state of the modified laminate under uniaxial loading matches with the biaxially loaded laminate. With a modified off-axis lamina orientation and the additional load amplitude from the biaxially loaded laminate, a simplified uniaxial testing laminate can be designed that yields the same biaxial tunnelling crack tip conditions.
Highlights
Over the past few decades, fibre reinforced polymer composites (FRP) have been an excellent choice of material in several industry sectors like aerospace, automotive, marine and wind energy
Results shows that the tunnelling crack tip stress state of the modified laminate under uniaxial loading matches with the biaxially loaded laminate
For tunnelling cracks propagating in steady state condition, Beuth [11] and Ho and Suo [12] presented an energy accounting method to calculate the energy release rate
Summary
Over the past few decades, fibre reinforced polymer composites (FRP) have been an excellent choice of material in several industry sectors like aerospace, automotive, marine and wind energy. This is primarily due to their high strength and stiffness properties, combined with the low density. In one of the study by Nakamura and Kamath [10], it was shown that the energy release rate of a thin film crack bonded to a rigid substrate and oriented perpendicular to the loading direction reaches a steady state value (remains constant) when the crack length is approximately twice the ply thickness. The steady-state energy release rate found to be proportional to square of the applied stress and thickness of the lamina [12]
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