Matrix and Fibre Stiffness Degradation of a Quasi-isotrope Graphite Epoxy Laminate Under Flexural Bending Test

Abstract

The permanent research of reliability and precision for failure criteria is a major concern for proper dimensioning of composite structures. Discrepancies are observed between theoretical results based on laminated theory or finite element analysis [Greif, R. and Chapon, E. (1993). Investigation of Successive Failure Modes in Graphite Epoxy Laminated Composites Beams, Journal of Reinforced Plastics and Composites, 29; Echaabi, J., Trochu, F., Pham, F. X. T. and Ouelette, M. (1996). Theroretical and Experimental Investigation of Failure and Damage Progression of Quasi-Isotropic Graphite Epoxy Composites in Flexural Bending Test, Journal of Reinforced Plastics and Composites, 15(7)] and experiments. In order to investigate these problems, numerical simulations were carried out to study the behavior of graphite-epoxy [[+45/-45/90/0]3] laminates subjected to three point bending tests. Two approaches were followed. The first one is based on laminate theory with transverse shear. The successive failures, failure modes, progression of failure and the effect of the geometrical characteristics of the specimens were analyzed during loading. Various failure criteria have been studied to predict the load when the weakest ply fails under flexural bending. Traditional failure criteria and new ones taking into account physical considerations were used. These criteria are tested with two models of stiffness reduction to account for ply failure. The second approach is based on a finite element analysis of laminate, in which three-dimensional failure criteria were implemented. Finally, the results obtained with these two approaches are compared with theoretical and experimental predictions of the scientific literature [Echaabi, J., Trochu, F., Pham, F. X. T. and Ouelette, M. (1996). Theroretical and Experimental Investigation of Failure and Damage Progression of Quasi-Isotropic Graphite Epoxy Composites in Flexural Bending Test, Journal of Reinforced Plastics and Composites, 15(7)].

Failure behavior of composite laminates under four-point bending

“…[8][9][10][11][12][13][14][15] However, similar studies are quite limited in number for out-of-plane loads (i.e. bending moment, twisting moment, transverse force, or a combination of them), and the existing ones [16][17][18][19][20][21][22] are not comprehensive; only some chosen configurations were studied under outof-plane loads: [0 8 19 [(AE45/90/0) 3 ] s , 20 [5] 22 In these studies, usually three-point bending tests were performed. 16,17,[19][20][21] The disadvantage of this test setup is that the line force applied by the upper support causes non-uniform bending moment in the critical region of the plate.…”

Degradation model based on Tsai-Hill factors to model the progressive failure of fiber metal laminates

“…Also, as this study is limited to predictions based on lamina properties, the degradation models employed based on micromechanics are not studied. A degradation model, employing different degradation factors, is proposed in Irhirane et al 6 for FRPs. In case of fiber failure, the total stiffness discount method is adopted, whereas for matrix failures the stiffness is reduced by three successive values, that is, 0%, 50%, and 100%.…”

Failure behavior of laminated composite plates under anticlastic bending

“…A number of researchers previously examined the intralaminar failure behavior of laminated composites under various out-of-plane loads and investigated the validity of different failure criteria. Irhirane et al 10 compared the predictions of several static failure criteria for the first-ply and progressive failure of composite laminates under three-point bending with experimental results. Meng et al 11 investigated the effects of lay-up configurations on the damage initiation under three-point bending.…”