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Interlaminar edge stress analysis of composite cross-ply flat specimens

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Sommario

Si analizzano gli sforzi interlaminari di bordo in provini piani di materiale composito. Il metodo utilizzato si basa sul Principio dei Lavori Virtuali e sviluppa una formulazione ad elementi flniti, estendendo ľapproccio di De Saint Vénant alle travi anisotrope. Si prendono in considerazione laminati piani simmetrici cross-ply a quattro strati sottoposti a estensione uniassiale e si mette in rilievo ľimportante ruolo svolto dal sottile strato interlaminare di resina posto tra due stati di flbra. L'eventuale esistenza di singolarità nell'andamento degli sforzi al bordo libero viene esaminata attraverso I'uso di schematizzazioni via via più dettagliate. I risultati sembrano indicare la presenza di tali singolarità solo all'interno dello strato interlaminare limitatamente alla zona di interfaccia con lo strato di fibre a 90°. Infine si mostra come i risultati ottenuti siano in buon accordo con quelli ricavati da altri autori.

Summary

Interlaminar stresses in composite flat specimens are analysed by a method previously presented, apt to compute inertial and elastic properties of anisotropic beam. This method is based on the Virtual Work Principle (V. W.P.), and develops a finite element displacement formulation, extending the De Saint Vénant approach to anisotropic beams. In the present paper symmetric four cross ply flat laminates under uniaxial extension are considered, and the important role of the resin layer between two fibre plies is pointed out by means of a detailed stress analysis of interlaminar regions. Through the use of increasingly refined meshes the possible existence of singularities in the stress trend at the free edge is examined. The results obtained are shown to be in good accordance with those already available in the literature; furthermore the modellization of the interlaminar layer shifts the possible presence of a free edge singularity to the fibre ply/interlamina interface, showing on the contrary a non singular trend in stress field inside the interlaminar ply. This is important especially in view of the fact that, through this approach, natural boundary conditions are enforced at convergence by the V.W.P., without any a priori assumption.

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Authors and Affiliations

  1. Dipartimento di Ingegneria Aerospaziale, Politecnico di Milano, Italy

    Gian Luca Ghiringhelli & Giuseppe Sala

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  1. Gian Luca Ghiringhelli
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  2. Giuseppe Sala
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Ghiringhelli, G.L., Sala, G. Interlaminar edge stress analysis of composite cross-ply flat specimens. Meccanica 21, 151–158 (1986). https://doi.org/10.1007/BF01556697

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  • DOI: https://doi.org/10.1007/BF01556697

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