A semi-analytical method to predict net-tension failure of mechanically fastened joints in composite laminates

Abstract

A Finite Fracture Mechanics model is proposed to predict the net-tension strength of composite mechanically fastened joints. A modification of coupled stress-energy criteria is suggested to take properly into account the effect of the R-curve in determining the crack length corresponding to the unstable crack propagation. The proposed model works for quasi-isotropic laminates and it requires as input the longitudinal strength and the fracture toughness of the laminate. The predictions obtained show good agreement when compared with the experimental results.

Comparison between models based on a coupled criterion for the prediction of the failure of adhesively bonded joints

“…the energy that must be overcome by a crack located at a distance d to grow). It must be noted that, as the fracture toughness may depend on the modemixity and thus on the crack length, to be strictly consistent with the energy balance, c ( ) G d should be replaced in (1) by c ( ) G d defined in (2) as suggested by previous authors [30] [16].…”

Large damage capability of non-crimp fabric thin-ply laminates

“…One possibility is to take into account the effect of the R-curve in the analysis method. This has already been done to predict net-tension failure of mechanically fastened joints in composite laminates using the FFMs model [23], and no other analysis method seems to be able to account for this effect.…”

Simulation of the Mechanical Response of Thin-Ply Composites: From Computational Micro-Mechanics to Structural Analysis

“…For simple geometries and loading scenarios, analytical models can satisfactorily predict failure of composite laminates with smooth geometries [174,175,177] or notched configurations [11,16,31,36,46,69,76,115,116,191,193], as long as delamination is not the predominant failure mechanism. These models are particularly suited for material and lay-up screening and for preliminary design and optimisation of composite structures.…”

“…To overcome this limitation of the classical analysis methods, physically-based criteria [11,36,46,116] provide accurate predictions of the notched response of composite laminates without requiring fitting parameters or complex Finite Element Analyses (FEA). Only independently measured material properties are necessary, the laminate strength and the laminate fracture toughness or crack resistance curve.…”

“…5, a similar strategy to that proposed in Ref. [46] is adopted to account for the in-situ effect, but in the framework of new invariant-based phenomenological failure criteria for FRPs [39]. These new failure criteria are not only simpler, but due to their invariant formulation, a priori knowledge of the angle of the fracture plane is not required.…”