404 High-Density Adhesive Filler is an epoxy thickening additive developed for maximum physical adhesive properties in hardware bonding where high-cyclic loads are anticipated. It can also be used for filleting and gap filling with epoxy where maximum strength is necessary.
VIDEO: How to Guide for Adding Fillers to Epoxy
We recommend 404 High-Density filler as the most cost-effective and easiest-to-use filler for hardware/stud bonding. Even small amounts of High-Density adhesive filler help in reducing creep in the epoxy. We recommend a moderately loose slurry, the epoxy should be thick enough to stay in a horizontal hole but not overfilled. Too high a loading of 404 can result in possible air entrapment. Chopped glass fiber or carbon fiber can be added to the mix to increase the load carrying capability, but the additional cost and application difficulty are usually not worth it.
As mentioned above, we typically use 800 psi as the ultimate shear stress for the filled epoxy mix. This is a conservative value based on long term fatigue data. At this stress level, the epoxy is the limiting component. The interface between the fastener threads and the epoxy is the typical failure initiation point in fatigue. This is good. The fatigue failure mechanism for epoxy — cracking and gradual destruction of the matrix — gives some warning. A failure at the wood/epoxy interface or the loss of the bolt head is usually catastrophic.
Read more about bonding hardware with High-Density filler at Epoxyworks.com