F.-G. Buchholz

INVESTIGATION OF MIXED MODE I/II INTERLAMINAR FRACTURE TOUGHNESS OF LAMINATED COMPOSITES BY USING A CTS TYPE SPECIMEN

Abstract The interlaminar fracture behavior of a unidirectionally glass fiber reinforced composite under the full range of in-plane loading conditions has been investigated. Loading conditions from pure mode I through various mixed mode I/II ratios up to pure mode II have been generated by the aid of the proposed compound version of the CTS (compact tension shear) specimen. From the experimentally measured critical loads, the mode I, mode II and the various mixed mode I/II critical energy release rates at crack initiation have been determined by the aid of the finite element method and the modified virtual crack closure integral method. Based on these results the parameters for a fracture criterion for the composite under consideration have been determined.

Finite element estimates of strain energy release rate components at the tip of an interface crack under mode I loading

The strain energy release rate components

Fracture analyses and experimental results of crack growth under general mixed mode loading conditions

G_{I}

Computational fracture analysis of different specimens regarding 3D and mode coupling effects

and

Numerical and experimental analysis of residual stresses for fatigue crack growth

G_{II}

MODE I, MODE II, AND MIXED-MODE I/II INTERLAMINAR FRACTURE TOUGHNESS OF GFRP INFLUENCED BY FIBER SURFACE TREATMENT

in mode I and mode II at the tip of an interface crack in a bimaterial plate under tension in a direction normal to the interface were evaluated using finite element analysis and Modified Crack Closure Integral (MCCI) technique. Three models, namely the bare interface model, the resin layer model and the subinterface crack model were studied with two different material combinations with progressively decreasing crack tip element size Aa which is also the virtual crack extension considered in the MCCI evaluation. The finite element results for all the models show increasing mode II dominance as

Analytical- and computational stress analysis of fiber/matrix composite models

\Delta a \rightarrow 0

Comparison of Computational Crack Path Predictions with Experimental Findings for a Quarter-Circular Surface Crack in a Shaft under Torsion

. Interpretation of these results is meaningful if the virtual crack extension Au is identified as crack growth step size.

Comparison of DBEM and FEM Crack Path Predictions with Experimental Findings for a SEN-Specimen under Anti-Plane Shear Loading

Abstract In this paper detailed results of 3D finite element (FE) and mixed mode analyses of different fracture specimens are presented and discussed. Special interest is taken in 3D and mode coupling effects to be found in strain energy release rate (SERR) results along crack fronts, in particular adjacent to corners, where a crack front intersects a free surface of a specimen. It will be shown that these effects stay small if they are related to Poisson’s ratio but that they can also be considerably pronounced if they are related to the global deformation behaviour of the specimen. The computational fracture analysis is based on the calculation of separated energy release rates (SERRs) by the aid of the modified virtual crack closure integral (MVCCI)-method in order to calculate the local SERR-distributions along the crack front. Furthermore some qualitative experimental results will show the influence of these variable mixed mode I, II and III loading conditions along the crack front on crack initiation and on the further development of 3D crack growth in the specimens.

Computational Simulation and Experimental Results on 3D Crack Growth in a 3PB-Specimen with an Inclined Crack Plane

Abstract In this paper computational fracture analysis results for four different specimens are presented and discussed with regard to 3D and mode coupling effects. The specimens under consideration are a center cracked tension specimen, with a crack inclined to the loading direction, a single edge notch specimen under out-of-plane shear deformation, a quarter circular corner crack specimen subject to shear deformation and a three point bending specimen with a crack inclined to the mid plane between the supports. The numerical fracture analysis results are based on two different approaches. The stress intensity factor results are determined from the singular stress fields along the crack front and the strain energy release rate results are obtained by means of the modified virtual crack closure integral method. In all cases under consideration the computational results from the two different approaches agree very well. Furthermore, the agreement with the global behavior of the reference solutions is also good. However, significant deviations are found between the computational and the reference results regarding local 3D and mode coupling effects, which seem not to be covered sufficiently by the reference solutions available in stress analysis handbooks or the literature.