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

Abstract

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.

A new approach for determining the R-curve in DCB tests without optical measurements

“…Nevertheless, this effect was not observed in the specimens tested. Moreover, piano hinges will be used in the tests in order to minimize the dependence of the deformation on the grips applied to load transfer [30].…”

Influence on the delamination phenomenon of matrix type and thermal variations in unidirectional carbon-fiber epoxy composites

“…In this study, instead of attaching the specimens to the grips by means of adhesive blocks or hinges as specified in the standard, a 15‐mm deep by 2‐mm thick notch was made on the film area of the specimens using an IsoMet 4000 Linear Precision Saw (Buehler). This notch was made to attach mechanical grips similar to those used by Blanco et al , although modified by Viña et al in their studies on the delamination of composite laminates in Mode I, and similar to that used by Brandt in a previous study , Fig. .…”

Investigating the effects of loading system on the fracture behavior of DCB specimens considering T-stress

“…As it can be seen in Figure 1, three useful and more practical methods are: drilled holes, piano hinges, and end load blocks. 11 Drilled holes are only applicable for relatively thick and tough substrate material and could not be used for composite laminates (for example see Borges et al. 12 ) Although the piano hinge has been accepted as a standard loading device for DCB specimens, the quality of bonding area, proper alignment of the hinges, and stiffness of the hinges can affect the results.…”