Enhancing vitrimer composite repairability via hybrid carbon/flax reinforcement
Topic(s) : Special Sessions
Co-authors :
Killian BOURDON (LUXEMBOURG), Daniel SCHMIDT (LUXEMBOURG), Tim HUBER (LUXEMBOURG)Abstract :
“Vitrimers” as we now know them – polymer networks capable of thermally activated associative covalent bond exchange – were first described by Montarnal et al as potential matrix materials for repairable composites [1,2]. Perrin et. al recently studied the effect of healing time on carbon fibre benzoxazine vitrimer composite performance focusing on the poly(PEG400-DPA-mea75/fa25) vitrimer developed by Adjaoud et al [3,4]. They showed that, at 170°C and with an applied pressure of 10 MPa, extended healing durations lead to improved recovery following a single healing cycle but diminished the overall capacity of the material to be repeatedly repaired when compared to shorter healing cycles.
In addition to their capacity for healing and repair, another means of potentially reducing the ecological impact of vitrimer composites is by increasing their bio-based content. In this context, we have identified carbon/flax hybrid fibre composites as a promising solution, given the potential to balance mechanical performance, cost and sustainability through the use of multiple types of reinforcing fibres. However, flax and carbon fibres differ significantly in terms of their mechanical and thermal properties and surface chemistry, all of which may influence bond exchange and healing performance. Given that the distribution of stresses and strains within such a hybrid composite will depend on its composition and structure, the type, content, and location of the different reinforcing fibres are expected to influence the healing process as well.
With this in mind, we investigate how the arrangement of carbon and flax fibres in inter-ply hybrid benzoxazine vitrimer composites influences their repairability, using the same matrix described by Perrin et al.
First, composites were prepared by vacuum assisted compression resin transfer moulding. Next, composite morphology and mechanical performance were assessed by X-ray micro-computed tomography (micro-CT) and interlaminar shear strength (ILSS) measurements, respectively. Following mechanical failure, a hot press-based healing process was applied with pressure and temperature were varied, and the healed composites were once more characterized to determine the impact of the stacking sequence.
Under optimal conditions, superior healing was observed in a range of hybrid composites compared to pure carbon and pure flax composites. It was observed that both the position and content of flax fibres in the hybrid composite were important in determining the optimal healing conditions and the extent of ILSS recovery. These results highlight the potential advantages of hybrid vitrimer composites in terms of repairability and lifetime extension.
In addition to their capacity for healing and repair, another means of potentially reducing the ecological impact of vitrimer composites is by increasing their bio-based content. In this context, we have identified carbon/flax hybrid fibre composites as a promising solution, given the potential to balance mechanical performance, cost and sustainability through the use of multiple types of reinforcing fibres. However, flax and carbon fibres differ significantly in terms of their mechanical and thermal properties and surface chemistry, all of which may influence bond exchange and healing performance. Given that the distribution of stresses and strains within such a hybrid composite will depend on its composition and structure, the type, content, and location of the different reinforcing fibres are expected to influence the healing process as well.
With this in mind, we investigate how the arrangement of carbon and flax fibres in inter-ply hybrid benzoxazine vitrimer composites influences their repairability, using the same matrix described by Perrin et al.
First, composites were prepared by vacuum assisted compression resin transfer moulding. Next, composite morphology and mechanical performance were assessed by X-ray micro-computed tomography (micro-CT) and interlaminar shear strength (ILSS) measurements, respectively. Following mechanical failure, a hot press-based healing process was applied with pressure and temperature were varied, and the healed composites were once more characterized to determine the impact of the stacking sequence.
Under optimal conditions, superior healing was observed in a range of hybrid composites compared to pure carbon and pure flax composites. It was observed that both the position and content of flax fibres in the hybrid composite were important in determining the optimal healing conditions and the extent of ILSS recovery. These results highlight the potential advantages of hybrid vitrimer composites in terms of repairability and lifetime extension.