Syndesil
Syndesil
Fiber-reinforced composites are strong but brittle — their connections fail with no warning. Syndesil puts a sacrificial ductile fuse in a parallel load path so the metal yields first, warns, and holds residual capacity.
Apply load, drag the joint, or run reversed seismic cycles — then tune the fuse yield and slip clearance and watch ductility, warning, and residual capacity recompute in real time.
Below the fuse yield load, the primary interface carries service demand. Both connections behave identically here.
Lower Pf yields earlier — more ductility and a wider warning margin, with lower residual; higher Pf carries more load and absorbs more total energy. Larger Δ buys ductility before the redundant path engages. Hold Pf < P0 and the failure mode is yours to design.
Composites carry enormous load for their weight and never corrode — but they're linear-elastic to failure. Push a composite connection to its limit and it ruptures at once: no yielding, no visible deformation, near-zero residual strength. That's the opposite of what codes and engineers require of a life-safety load path, and it's why composites rarely reach primary structure.
Adhesive joints reach high capacity but fail abruptly and unpredictably — sensitive to surface prep, heat, moisture, creep, and age. No ductility, no warning.
Fasteners through the laminate concentrate stress and cut load-bearing fibers, inviting bearing failure, net-section rupture, and delamination — all with sudden onset.
Combining bond and bolt helps capacity but adds no ductility. When the governing brittle mechanism is spent, the joint is still spent — at once.
Proportion the metal fuse to yield at a load below the brittle capacity of the composite interface. Then the fuse — not the composite — governs how the connection fails. Hold that hierarchy across overstrength, strain hardening, heat, and age, and the failure mode is yours to design.
Two cooperating load paths engage in sequence. The result is a connection that deforms visibly, dissipates energy, and keeps holding — converting a single brittle event into a controlled progression.
Service load runs through the primary bonded or bearing interface. The fuse rides along elastically; the redundant path sits idle.
At the fuse yield load the metal yields and deforms visibly, dissipating energy while the composite stays intact. This is the warning brittle joints never give.
Continued movement reaches a tuned clearance — a slotted hole or calibrated slip — and the secondary mechanical path comes into bearing.
Even if the primary interface is compromised, the redundant path carries a quantifiable residual load. The connection degrades; it does not vanish.
Pultruded or laminated CFRP, GFRP, aramid, or basalt — coupled through a load-distributing termination so no single fiber bundle governs.
Bond, bearing, or both. Carries all service load — and defines the brittle capacity P0 the fuse is tuned beneath.
A yieldable metal coupon, perforated plate, shear link, or buckling-restrained bar with a reduced section. Yields first; inspectable; replaceable after an event.
A pin in a slotted hole, key, or supplementary anchor that stays idle until a tuned displacement, then carries residual load independently.
Anywhere a brittle composite element meets ductile structure and the failure mode matters.
A pultruded composite beam seats to a steel column; the fuse yields before the bonded and bolted interfaces, slotted pins form the residual path.
The fuse yields before bond failure or a concrete breakout cone; supplementary anchors engage after slip to retain capacity.
The connection becomes the ductile, energy-dissipating end of a lightweight, corrosion-immune composite diagonal brace — the loop you traced above.
Composite bridge decks to girders, shear and cladding panels to frames, and FRP-rebar couplers — each with the fuse and sequenced path interposed.
Bonded and bolted joints inherit the composite's brittleness. The all-steel structural fuse — the closest prior art — supplies ductility but was never built to protect a brittle composite across a dissimilar-material junction. Syndesil does both.
| Property | Bonded | Bolted | All-steel fuse | Syndesil |
|---|---|---|---|---|
| Ductility at the joint | none | none | high | high |
| Warning before failure | no | no | yes | yes |
| Residual capacity | ~0 | low | varies | designed |
| Protects a brittle composite | n/a | n/a | not its job | core |
| Replace after an event | no | partial | sometimes | yes |
| Corrosion-immune member | yes | yes | no | yes |
The all-steel structural fuse (reduced-beam-section, yielding links, buckling-restrained braces) is the family the FTO search will target first. Syndesil's claims carve the novelty around protecting a brittle dissimilar-material junction with sequenced engagement and a residual path.
The novelty is the architecture — a parallel metallic fuse tuned beneath the brittle interface, plus a displacement-sequenced residual path. That sidesteps the crowded composite-composition art and anchors the claim on behavior.
A ligament joins rigid bone, yet sprains before it tears.The connection that does the same between composite and steel
This page is built and staged but must not go live until the provisional (SYND-001-PROV) is on file and employment-IP clearance is confirmed. This venture sits outside Mercury Paper's field of business, so the §13.5 / Cal. Lab. Code §2870 framework is expected to clear — confirm before deploying.