United Technologies Corporation

Jong-Min Ha

James R Dunphy

Robert M Rukus

Resin curing of a composite laminated structure is monitored using an optical fiber 20 having a grating sensor 28 embedded therein. The fiber 20 is surrounded by upper and lower buffer regions 12,14 having a predetermined minimum number of layers 30 (or thickness) with uni-directional reinforcing filaments 32 and resin 34 therebetween. When the filaments 32 are oriented perpendicular to the longitudinal axis of the fiber 20, the buffer regions 12,14 allow the sensor 28 to exhibit maximum sensitivity to detection of the minimum resin viscosity and the gelation point (i.e., the onset of a rapid crosslinking rate) of the resin 34. The buffer regions 12,14 also have a minimum thickness which serve to isolate the sensor 28 from interfering stresses from arbitrarily angled filaments 32 in layers 30 of outer regions 10,16 which surround the buffer regions 12,14.

Composite structure resin cure monitoring apparatus using an optical

An optical fiber entry strain relief interface includes a composite structure (lay-up) 10 having an optical fiber 20 embedded therein. The optical fiber 20 enters (or exits) the lay-up 10 at at least one point 24 and passes through transition layers 47 comprising an adhesive film 42, a thin rubber sealing layer 44, and a thick rubber strain relief layer 46, and through a polymer plug 48 located above the layer 46. The lay-up is consolidated by heating the lay-up over a temperature profile and applying pressure through mostly closed compression molding tools 30,32. The adhesive film 42 bonds the adjacent layer 44 to the upper surface of the lay-up 10, the sealing layer 44 becomes soft enough to seal around the fiber 20 at a temperature lower than the temperature at which the resin 16 exhibits a low enough viscosity to leak out of the lay-up 10, thereby preventing the resin from leaking out of the lay-up 10 during lay-up consolidation, the strain relief layer 46 provides a rubber strain relief for the optical fiber 20, and the plug 48 supports the layers 47 during consolidation.

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Seoul, South Korea

Jong-Min Ha