Abstract
Polymer-based composites are becoming widely used for structural applications, in particular in the aeronautic industry. The present investigation focuses on the mechanical integrity of an epoxy resin of which possible damage results in limitation or early stages of dramatic failure. Therefore, a coupled experimental and numerical investigation of failure in an epoxy resin thermoset is carried out that opens the route to an overall micromechanical analysis of thermoset-based composites. In the present case, failure is preceded by noticeable plasticity in the form of shear bands similar to observations in ductile glassy polymers. Thus, an elastic-visco-plastic constitutive law initially devoted to glassy polymer is adopted that captures the rate- dependent yield stress followed by softening and progressive hardening at continued deformation. A general rate-dependent cohesive model is used to describe the failure process. The parameters involved in the description are carefully identified and used in a finite element calculation to predict the material’s toughness for different configurations. Furthermore, the present work allows investigation of nucleation and crack growth in such resins. In particular, a minimum toughness can be derived from the model which is difficult to evaluate experimentally and allows accounting for the notch effect on the onset of failure. This is thought to help in designing polymer-based composites.
Highlights
Epoxy resins are used as a matrix in a large number of thermoset- based composites due to the large number of components that can react with the epoxy resin to form composites with a very wide range of properties [1]
A coupled numerical and experimental methodology to model and characterize the failure of an epoxy thermoset is presented. This is considered for a low cross-link density epoxy of which bulk mechanical response is similar to that of ductile polymers
Its mechanical response is realistically described by the Boyce et al model (1988) in the absence of failure, but any formulation able to capture softening upon yielding and hardening at continued deformation could be used
Summary
Epoxy resins are used as a matrix in a large number of thermoset- based composites due to the large number of components that can react with the epoxy resin to form composites with a very wide range of properties [1]. It is necessary to gain insight in the fracture response and the mechanisms underlying failure of epoxy resin under various loading rates for reliable design in engineering applications. The fracture mechanism in epoxy resins remains to be identified and at the moment there is no general agreement in the thermosets community about the physics underlying failure. In thermosets with a high cross-link density, Kinloch [2] considers that crazing as observed in glassy polymers is not likely to occur. The main argument for this point of view is that chain disentanglement or chain scission is not likely to take place in thermosets while this is key in the formation of the web of fibrils. Some evidence of craze-like structures are reported in toughened or low cross-linked thermosets [3,4,5]. When bulk viscoplasticity takes place prior to Polymers 2018, 10, 1321; doi:10.3390/polym10121321 www.mdpi.com/journal/polymers
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
