Influence of Ply Sequence and Thermoelastic Stress Field on Asymmetric Delamination Growth Behavior Emanating From Elliptical Holes in Laminated FRP Composites

The present study encompasses the influence of ply sequence and thermoelastic stress field on asymmetric delamination growth behavior emanating from elliptical holes in laminated fiber reinforced polymeric composites. Results, emphasizing the effect of thermal residual stresses on delamination growth behavior of the composite laminates subjected to two different loading conditions, i.e., in-plane tensile and compressive loadings, are presented. Two sets of full three-dimensional finite element analyses have been performed to calculate the displacements and interlaminar stresses along the delaminated interfaces responsible for the delamination onset and propagation. Modified crack closure integral methods based on the concepts of linear elastic fracture mechanics have been followed to evaluate the individual modes of strain energy release rates along the delamination front. In each case, the delamination is embedded at a different depth along the thickness direction of the laminates. It is observed that the fiber orientation of the plies bounding the delamination front significantly influences the distribution of the local strain energy release rate. Also, the residual thermal stresses have a detrimental effect on the laminates subjected to compressive loading and more so in the case of laminates with delaminations existing closer to the top and bottom surfaces of the laminate.

Transient Thermoelastic Stress Fields in a Half-Space

Computing the thermoelastic stress field of a material subjected to frictional heating is essential for component failure prevention and life prediction. However, the analysis for three-dimensional thermoelastic stress field for tribological problems is not well developed. Furthermore, the pressure distribution due to rough surface contact is irregular; hence the frictional heating can hardly be described by an analytical expression. This paper presents a novel set of frequency-domain expressions (frequency response functions) of the thermoelastic stress field of a uniformly moving three-dimensional elastic half-space subjected to arbitrary transient frictional heating, where the velocity of the half-space, its magnitude and direction, can be an arbitrary function of time. General formulas are expressed in the form of time integrals, and important expressions for constant velocities are given for the transient-instantaneous, transient-continuous, and steady-state cases. The thermoelastic stress field inside a translating half-space with constant velocities are illustrated and discussed by using the discrete convolution and fast Fourier transform method when a parabolic type or an irregularly distributed heat source is applied.