Closed Loop Cure Control

Thermal Kinetics

Real time sensor arrays measure dielectric permittivity or ultrasonic wave attenuation inside the mould cavity to track molecular mobility as crosslinking proceeds. Transducers embedded within the tooling face transmit frequency shifts to a central processor, which compares actual reaction velocity against a preprogrammed kinetic model. Controllers modulate platen heating fluid temperatures or induction coil wattage instantly, suppressing exothermic runaway spikes before volatile entrapment occurs.

Thermal conduction lags behind chemical exotherms in thick composite structures, forcing the algorithm to anticipate cooling requirements well ahead of the actual temperature peak. Platen heaters fail to remove heat fast enough once an over accelerated reaction begins, leading to matrix charring near the tool interface and unreacted monomers at the geometric centre. Sensor placement determines measurement accuracy, because misplaced probes record boundary layer conditions instead of bulk core reactions.

Viscosity Dynamics

Molecular weight growth during crosslinking alters flow properties exponentially before gelation locks the spatial network in place. Viscosity measurements govern the transition from liquid infusion to solid consolidation, dictating when external consolidation pressure must increase to expel excess volatiles. Pressure applications arriving too early squeeze out liquid resin and create fiber dry spots, while late interventions trap microscopic voids within the structural laminate.

Rheological testing establishes the minimum viscosity window for consolidation, ensuring uniform fiber wetting without resin starvation. Temperature gradients across large tooling surfaces cause differential viscosity drops, forcing the control system to zone heating inputs independently across distinct mould sectors. Material lot variations shift the gel time curve unpredictably, demanding adaptive algorithms that recalibrate reaction rates during the injection phase rather than relying on static recipe files.

Yield Verification

Post cure audit procedures measure glass transition temperatures and inter laminar shear strengths to confirm that the feedback loop maintained stoichiometry throughout the operational cycle. Destructive coupon testing validates crosslink density against design allowables, ensuring structural integrity under maximum operating loads. Ultrasonic C scan inspections map internal porosity distributions, revealing whether localised temperature excursions generated micro cracking or delamination zones.

Process logs record every thermal adjustment and sensor response, providing a traceable quality pedigree for safety critical aerospace and marine components. Deviations between predicted and measured exotherm curves trigger automatic quarantine flags, preventing substandard assemblies from advancing to machining operations. Full conversion data eliminates destructive testing requirements for routine production runs, replacing physical coupons with certified process signatures.