The performance limiting factor for all general composite repairs (carbon or glass encased in an epoxy resin) is the strength of adhesion.The adhesive layer between the steel component and the composite laminate will be the first failure mechanism to occur in the situation where the load on the repaired component is slowly increased. This is true no matter if the defect that has been repaired in the component is through wall or not. In other words, it is not the strength of the composite laminate that is critical but rather it is the load transfer into the composite laminate that is limited by the failure in the adhesive layer (often termed interfacial delamination).
Therefore, when developing our composite repair system FutureWrap most attention was be paid to the strength of adhesion and how that strength can be optimised. Physically what is happening at the interface between the epoxy resin and the steel component that manifests itself as adhesion are two effects. One is a covalent bond between the epoxy and the steel, the other is mechanical interlocking, a physical interaction or locking between the roughness of the steel surface the epoxy resin. There is some debate about the relative importance of these two effects, with the majority of current opinion favouring the covalent bonding as the primary effect.
To enhance FutureWrap adhesion therefore the epoxy resin should cover or wet out as much of the steel surface as possible to ensure the maximum area over which these covalent bonds can act. When developing Futurewrap composite repairs maximising the surface contact between the resin and steel surface was a key consideration.
Further blogs will follow which will go into more detail about how this surface contact was maximised for Futurewrap repairs, specifically enhancing the covalent bond and epoxy resin wet out.
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