The mechanical properties of adhesives should be designed by careful selection of resin chemistry (e.g. epoxy, polyurethane, acrylate, polyamide, etc.) to match those of the substrate materials, thereby adding to the strength of the finished product. To achieve the optimum bond strength, it is important to: Source:https://www.adhesives.org/resources/knowledge-center/aggregate-single/adhesives-for-composites
`Clean surfaces free from dust or debris;
`Abrade or energize the surfaces to be bonded;
`Use appropriate adhesive for the application;
`Provide uniform bondline thickness, and constant clamping pressure along bondline until complete cure.
Conventional two-component epoxy adhesives are extensively used in the automotive industry to bond SMC, SRIM (structural reaction injected molding), and other substrates. However, many of these epoxy systems, particularly polyamide-based systems, have undesirably long open times and require post-baking in order to achieve full cure of the adhesive composition. This problem could be overcome by incorporation of a coupling agent with the epoxy resin and by using aliphatic amines as part of the curative.Acrylate monomers may be incorporated in the epoxy resins to further adjust open time and improve adhesion, in particular, to metal substrates.
An improved method and apparatus for fabricating adhesive fillers can reduce processing time and labor costs by extruding the fillers either directly onto a composite structural member in order to fill a void in a composite structure, or onto a tool that may be used to maintain the cross-sectional shape of the filler and place the shaped filler on a structural member. This method may substantially eliminate the need for prefabricating and storing fillers.