Assessment of microcapsule—catalyst particles healing system in high performance fibre reinforced polymer composite

Abstract

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms Assessment of microcapsule -catalyst particles healing system in high performance fibre reinforced polymer composite. AbstractAutonomous self-healing in carbon fibre reinforced polymer (CFRP) is demonstrated using epoxy resin filled microcapsules and a solid-state catalyst. Microcapsules filled with oligomeric epoxy resin (20-450 µm) and particles of Sc(OTf) 3 are embedded in an interleave region of a unidirectional CFRP laminate and tested under mode I loading. Double cantilever beam (DCB) test specimens containing variable concentrations of microcapsules and catalyst were prepared, tested and compared to those healed by manual injection with corresponding healing resin formulation. The healing efficiency was evaluated by comparing the maximum peak load recorded on load-displacement curves for pristine and healed specimens. A 44% maximum recovery was observed for specimens containing 10wt% of solid phase catalyst and 11wt% of epoxy microcapsules. However, a significant (80%) decrease in initial strain energy release rate (G IC ) was observed for specimens with the embedded healing chemistries. Visual abstractEpoxy filled microcapsules with poly(urea-formaldehyde) shell wall after synthesis (left) and following fracture testing. 500#µm## 500#µm##

Progress in Self‐Healing Fiber‐Reinforced Polymer Composites

“…To the best of the authors’ knowledge, very few single or double capsule systems have been demonstrated in FRPs that meet the selection criteria specified. One exception published by Bolimowski et al utilizes the same chemistry as Coope et al to functionalize unidirectional (UD) composite specimens. Although Bolimowski et al did not report fiber volume fraction, it can be inferred from the cure procedure reported, and the manufacturer's data, that the sample fiber volume should be between 52% and 56%.…”

“…One exception published by Bolimowski et al utilizes the same chemistry as Coope et al to functionalize unidirectional (UD) composite specimens. Although Bolimowski et al did not report fiber volume fraction, it can be inferred from the cure procedure reported, and the manufacturer's data, that the sample fiber volume should be between 52% and 56%. Double‐cantilever beam (DCB) specimens demonstrated a maximum healing efficiency of 44% with a catalyst loading of 10 wt%; however, even this modest recovery is amplified by the significant detrimental effect the inclusion of the microcapsules and catalyst particles has on initial fracture toughness: the strain energy release rate of the virgin‐functionalized specimens only averaged 22% of that of the nonfunctionalized control specimens.…”

“…Although it would be imprudent to draw conclusions about the validity of microcapsule/catalyst systems from a single study, and only based upon recovery of fracture toughness, it nevertheless raises questions about the effectiveness of this approach when employed in an FRP compared with a bulk polymer. It should also be noted that Bolimowski et al observed an average of 14% recovery in peak load in samples with no catalyst present, suggesting a significant contribution from the solvent‐induced polymer reptation between the host matrix and the healing agent, further questioning the effectiveness of the microcapsule/catalyst system.…”

“…The findings of Bolimowski et al and Manfredi et al hint at the disparate outcomes achieved when self‐healing systems are applied to materials that either meet or fall short of the structural parameters defined at the outset. Future work needs to focus on the ability of self‐healing to address the greater loading that will typically be imparted to high‐performance FRPs, which are not present in low fiber volume or bulk polymer materials.…”

“…Although the host FRPs investigated thus far have typically been prepared via simple hand lay‐up or infusion techniques, several additional techniques have been utilized to incorporate the self‐healing functionality . Autoclave compaction of preimpregnated plies has also been explored with capsules, as reported in Bolimowski et al Adaptation in the cure and postcure temperature may however be required. As an example, for microencapsulated healing systems, the temperature needs to be carefully chosen to avoid damaging the microcapsules, whereas in latent functionality systems, appropriate cure schedules need to be defined in order to achieve the right amount of latent functionality.…”