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Steel and Composite Structures
  Volume 35, Number 3, May10 2020, pages 439-447

Thermoelastic effect on inter-laminar embedded delamination characteristics in Spar Wingskin Joints made with laminated FRP composites
P.K. Mishra, A.K. Pradhan, M.K. Pandit and S.K. Panda

    This paper presents two sets of full three-dimensional thermoelastic finite element analyses of superimposed thermo-mechanically loaded Spar Wingskin Joints made with laminated Graphite Fiber Reinforced Plastic composites. The study emphasizes the influence of residual thermal stresses and material anisotropy on the inter-laminar delamination behavior of the joint structure. The delamination has been pre-embedded at the most likely location, i.e., in resin layer between the top and next ply of the fiber reinforced plastic laminated wingskin and near the spar overlap end. Multi-Point Constraint finite elements have been made use of at the vicinity of the delamination fronts. This helps in simulating the growth of the embedded delamination at both ends. The inter-laminar thermoelastic peel and shear stresses responsible for causing delamination damage due to a combined thermal and a static loading have been evaluated. Strain energy release rate components corresponding to the Mode I (opening), Mode II (sliding) and Mode III (tearing) of delamination are determined using the principle of Virtual Crack Closure Technique. These are seen to be different and non-self-similar at the two fronts of the embedded delamination. Residual stresses developed due to the thermoelastic anisotropy of the laminae are found to strongly influence the delamination onset and propagation characteristics, which have been reflected by the asymmetries in the nature of energy release rate plots and their significant variation along the delamination front.
Key Words
    delamination; strain energy release rate; Spar Wingskin Joint; thermoelastic; virtual crack closure technique
P.K. Mishra and S.K. Panda: Department of Mechanical Engineering, Biju Patnaik University of Technology, Rourkela, Odisha, India
A.K. Pradhan and M.K. Pandit: School of Mechanical Sciences, Indian Institute of Technology, Bhubaneswar, India

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