Exploring durability of interfaces in flax fibre/epoxy micro-composites

Abstract

The influence of wet aging on the behaviour of flax/epoxy micro-composites composed of single flax fibres embedded in epoxy micro-droplets has been studied. Interfacial shear strength has been examined by debonding the micro-droplets. The apparent interfacial shear strength decreases with immersion time in water, dropping rapidly during the first 15 min of immersion then stabilizing. Drying samples after short immersion periods allows recovery of properties, indicating a plasticization mechanism. For longer immersion times irreversible degradation is observed. Scanning electron microscopy reveals fibre surface peeling, indicating that an internal interface within the fibre is weaker than the fibre/matrix interface after aging. A simple descriptive model has been used to identify diffusion kinetics, with a critical diffusion time corresponding to a change in degradation mechanism.

Interfacial properties of flax fibre–epoxy resin systems: Existence of a complex interphase

“…Cell-wall layer interfacial failure, called peeling has been widely observed (Fig. 2C) confirming previous observations [11]. Similar observations can be done with Electra fibres (not shown here).…”

“…Microbond samples and characterization are done following the same protocol as described elsewhere [11]. The apparent shear strength at debonding (s app ) is calculated using (Eq.…”

“…Recently, Le Duigou et al [11] have shown that wet aging an epoxy microdroplet on single flax fibre induces reduction of interfacial shear strength but IFSS remains almost constant around 10 MPa. Mechanisms which are responsible for durable bond strength between flax and epoxy are still open to discussion.…”

Shear strength and fracture toughness of carbon fibre/epoxy interface: effect of surface treatment

“…For fibres without the surface treatment, interfacial separation was the main failure mode, indicative of poor adhesion (Figure 11(b)). There was no residual epoxy on the surface of fibres, which is a direct evidence of weak interface [27]. For fibres with the surface treatment, most of the droplets failed in a cohesive failure mode (Figure 11(c)).…”

Homogenization of carbon/polymer composites with anisotropic distribution of particles and stochastic interface defects

“…It is widely known that the interface defects appearing between different phases of composites (like a matrix and its reinforcement) play a crucial role in reliability, durability and failure of these materials [1][2][3]. Generally, structural defects in composites may reflect some manufacturing imperfections [4], following remarkable residual thermal stresses for instance, and may exhibit spherical or ellipsoidal shapes, at least for polymeric materials [5], resulting from the well-documented matrix cavitation processes [6].…”