Influence of moisture and drying on fatigue damage mechanisms in a woven hemp/epoxy composite: Acoustic emission and micro-CT analysis

Abstract

For the last 20 years, plant fibres have emerged as an alternative to glass fibres in composites.However, a crucial issue with plant fibre composites is their durability, i.e. their long-term hygrothermal and fatigue performances. This study deals with the influence of different conditionings (Ambient, Wet and Wet/dry) on the fatigue behaviour of [(±45)] 7 hemp/epoxy composites. The induced damage mechanisms are investigated by acoustic emission and micro-CT. Results show that the Wet samples exhibit the lowest fatigue sensitivity despite their greatest damage quantity, whereas the Wet/dry specimens behave like pre-damaged Ambient ones.Micro-CT scans show that the same type of damage appears in all cases: cracks are made of a coalescence of partial debondings at hemp yarn/matrix interfaces, which can lead to macro-cracks crossing the sample thickness.Moreover it is demonstrated that, during fatigue tests, the evolution of cumulative AE energy and hysteresis loop energy, and the evolution of damage quantity measured by micro-CT and final hysteresis energy, are very similar whatever the conditioning.

Fatigue behaviour of flax-basalt/epoxy hybrid composites in comparison with non-hybrid composites

“…Among these, it is possible to find the model proposed by D'Amore et al, based on the residual strength degradation of the composite [47]. This model was developed for glass-mat-reinforced thermoset based composites, but it was proved to be able to successfully predict the fatigue behaviour of continuous glass fibre reinforced composites [48,49] and woven hemp/epoxy composites [25]. The model proposed by D'Amore et al was used as a basis for the development of the Epaarachchi and Clausen model [50], used in the present study.…”

“…off-axis plies, moisture content, fibre crimp, 'out-of-plane' weaves in fabric) are all influencing longevity of plant fibre composites. Regarding the moisture content, Barbiere et al [25] have recently demonstrated the influence of the storage and the testing conditions on fatigue behaviour of a woven hemp/epoxy composite. Liang et al [26], in their study, showed that the [±45] 3S flax/epoxy specimens offer better specific fatigue endurance than similar glass/epoxy laminates, which was not the case for the [0/90] 3S specimens.…”

Influence of the stress level and hygrothermal conditions on the creep/recovery behaviour of high-grade flax and hemp fibre reinforced GreenPoxy matrix composites

“…Indeed, contrary to most petrosourced composites, PFCs are highly sensitive to hygrothermal conditions and their variation and/or cycling over time [13]. Their monotonic, fatigue and vibrational behaviours are reported to be significantly influenced by such parameters [8,9,[14][15][16][17][18][19].…”

Hemp From Disordered Lines for New Staple Fibre Yarns and High-Performance Composite Applications

“…Hybrid composites exhibit damage patterns that are mostly dominated by the higher fibre volume fraction of glass fibres and their location in the outermost layers (Boria et al, 2020). For applications that have to withstand dynamic loads, the determination of the fatigue behaviour of composites is also of particular interest (Yuanjian and Isaac, 2007;de Vasconcellos et al, 2014a;de Vasconcellos et al, 2014b;Fotouh et al, 2014;Shahzad and Isaac, 2014;Barbière et al, 2018;Barbière et al, 2020). Compared to GFC, HFC shows lower fatigue sensitivity and lower stiffness degradation at the same normalised peak stress levels and better resistance to crack formation (Yuanjian and Isaac, 2007;Shahzad and Isaac, 2014).…”