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Karel Matous



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Analysis of tongue and groove joints for thick laminates


K. Matous and George J. Dvorak

Department of Mechanical Engineering, Aeronautical Engineering and Mechanics
Rensselaer Polytechnic Institute
110 8th Street, Troy, NY 12180

Abstract


A finite element evaluation of local stresses in the adhesive and adherends is presented for a tongue-and-groove joint of a homogenized thick composite laminate to steel plate. The quasi-isotropic laminate is made of glass fabric/vinyl ester plies. Most results are obtained for elastic response of the Dexter-Hysol 9338 adhesive that was used in recent experiments (Dvorak, G.J., Zhang, J. and Canyurt, O., ``Adhesive Tongue and Groove Joints for Thick Composite Laminates'', Composites Science and Technology, 61, 1123-1142 (2001)). A nonlinearly viscoelastic adhesive is also considered, with illustrative properties taken from experiments on the FM-73 system. Both in-plane force resultants and out-of-plane moments are included in the applied loads. Scaling of the elastic results with regard to plate thickness shows that for given levels of overall stresses applied to the adherend plates, the stresses supported by the adhesive do not depend on plate thickness. Adhesive stress relaxation is shown to be relatively small, and occurring in a short time period.

Conclusions


The results illustrate the stress distributions encountered in adhesive tongue and grove joints of thick laminated composite plates. As in other joint configurations, the stress concentrations at the adhesive leading edge depend on the local geometry of the adherends. However, for given values of stresses in plate sections removed from the joint, the stresses in the joint remain independent of a plate thickness. This is a significant advantage that does not hold in conventional lap joints, and thus favors use of tongue and grove joints of different configurations in joining of thick laminates, where the unavoidable stress concentrations at the adhesive leading edge can be amply supported by the high in-plane strength of the laminated plate. Consideration of the viscoelastic response of the adhesive indicates a relatively small relaxation of the local stresses, within a fairly short time period.

Acknowledgment


The authors appreciate financial support of this work by the Ship Structures and Systems S&T Division of the Office of Naval Research. Dr. Yapa D.S. Rajapakse served as program monitor.
2009 Notre Dame and Dr. Karel Matous