Influence of the Matrix Type on the Mode I Fracture of Carbon-Epoxy Composites Under Dynamic Delamination

Engineering Fracture Mechanics

et al. 2017

Self Cite

The delamination phenomenon is one of the major failure mechanisms in composite materials formed by the stacking of successive layers. The fracture mode that has been studied the least within this phenomenon is mode III, due to the difficulty its simulation involves. A novel test device is presented in this paper that allows laminated composites to be subjected to this mode of loading. Characterization tests were carried out on two materials with different matrices in order to analyse the influence of the type of matrix in the fracture behaviour under mode III-fracture. Furthermore, two analytical models adapted to this test methodology have been used for the determination of the value of the energy release rate for this mode of loading in both materials. The load was applied at different distances from the front of the notch, this being another parameter that was analysed. From the results obtained it follows that the device used in this work allows a dominant mode III and that this result holds for different points of load application studied.

Section: Resultssupporting

confidence: 51%

Analysis of mode III interlaminar fracture toughness of laminated composites using a novel testing device

López-Menéndez

Engineering Fracture Mechanics

et al. 2017

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“…This device has been successfully used by the authors in several static and fatigue delamination tests 15–17 …”

Section: Further Modification Of the Mechanical Hingementioning

confidence: 99%

Influence of the Loading System on Mode I Delamination Results in Carbon-Epoxy Composites

Experimental Techniques

López

et al. 2011

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In this paper, a modified mechanical grip fitting is used to perform double cantilever beam (DCB) tests. The advantage of using mechanical grips instead of piano hinges or end blocks lies in the fact that the use of adhesive bonding is not required to fix the sample. Adhesive bonding can be an important source of uncertainty and unexpected debondings in fatigue tests. Mechanical fittings are also well suited for high temperature applications where adhesive bonds usually undergo premature failure. An experimental programme has been developed in order to compare the performance of the modified mechanical hinges with classical hinges and end blocks. The highest GIc values and scattering were found for the end block system, while hinges and mechanical hinges furnished similar results. The material used to perform the experimental study was a Hexcel AS4/3501‐6 unidirectional laminate.

“…More in-depth knowledge of the damage mechanisms implied in the process is thus needed, as well as the quantification of the resistance of the material against this phenomenon. Many test methodologies have been developed for this purpose, all of which are based on fracture mechanics, both in pure modes [1][2][3][4][5] and in mixed modes. [6][7][8] In this field, the most widely used mixed mode I/II methodology normalized by ASTM is the mixed mode bending (MMB) test, 9 although other methods have been developed in which the tooling is less complex and therefore the results are less dependent on the person conducting the test.…”

Section: Introductionmentioning

confidence: 99%

Fracture behavior under mixed mode I/II static and dynamic loading of ADCB specimens

Rubiera

Journal of Reinforced Plastics and Composites

et al. 2016

In this paper, the phenomenon of delamination under static and dynamic loading of a composite made of an epoxy matrix and carbon fiber reinforcement has been studied, analyzing its fracture behavior under mixed mode I/II loading employing an asymmetric double cantilever beam test. Under static loading, some of the most representative formulations for calculating the energy release rate were analyzed, finding a good agreement between the results obtained by means of the different formulations. Under dynamic loading, the number of cycles necessary for the crack onset was determined (determination of ΔG − N fatigue curves and number of cycles necessary for the delamination onset for a given energy release rate). As regards the experimental results, apparent fatigue limits of the order of 38% of the critical fracture energy were obtained for an asymmetry coefficient of 0.1. Subsequent statistical analysis of the results enabled the fatigue limit to be defined more accurately. This was found to be 15% for this material, indicating the need to use these tools for the actual determination of the infinite fatigue life of the material. Finally, an optical study of the fracture surfaces was carried out which confirmed the presence of mixed mode fracture typologies.