Abstract: Methods for making and curing resin-based adhesives are disclosed using encapsulated amine accelerators activated by providing ultrasonic energy.

Abstract: Ignition-quenching systems comprise an ignition-quenching cover configured to quench an ignition event in a combustible environment triggered by an ignition source associated with a fastener stack. The ignition-quenching cover comprises a porous body that is gas permeable and that has pores sized to quench ignition in the combustible environment. The ignition-quenching cover further comprises a cover attachment feature configured to mate with a fastener attachment feature of the fastener stack. The ignition-quenching cover is configured to cover the fastener stack, which may be associated with a potential ignition source that produces an ignition event in the combustible environment. The porous body may include one or more porous elements that may be formed of various polymeric, mesh, or fabric materials. The ignition-quenching cover may comprise a non-porous frame that is bonded to the porous body and that defines the cover attachment feature.

Abstract: Described herein is an apparatus for applying and curing a light-curable material on a work surface. The apparatus includes a nozzle from which the light-curable material is applied to the work surface to form a layer of light-curable material on the work surface. The layer of light-curable material has a leading edge and a trailing edge defined according to a direction of movement of the nozzle relative to the work surface. The apparatus also includes a light source fixed relative to the nozzle. The light source is operable to direct a light beam to the trailing edge of the layer of light-curable material.

Abstract: A low viscosity polysulfide sealant composition. The composition comprises a curable polysulfide polymer; a crosslinking agent; and a plurality of core-shell particles. The core-shell particles comprise: a core comprising a ferromagnetic material; and a shell comprising silica treated with an organic sulfur containing compound. The shell is capable of bonding with the polysulfide polymer.

Abstract: A low viscosity polysulfide sealant composition. The composition comprises a curable polysulfide polymer; a crosslinking agent; and a plurality of core-shell particles. The core-shell particles comprise: a core comprising a ferromagnetic material; and a shell comprising silica treated with an organic sulfur containing compound. The shell is capable of bonding with the polysulfide polymer.

Abstract: Cured flexible sealant may be removed from a substrate if the cured flexible sealant includes within its volume a susceptor such as metal susceptor particles. Removal proceeds by exposing the sealant with the susceptor to radio-frequency radiation sufficient to cause dielectric heating in the susceptor. The consequent heating in the cured sealant reduces the bond strength of the cured sealant. The reduced bond-strength sealant may be removed by physical methods, such as scraping etc., much more easily than the original (unexposed) cured sealant. Also disclosed are sealant compositions with susceptor, susceptor tools to introduce susceptor into cured sealant, and handheld radio-frequency heaters to apply radio-frequency radiation to cured sealant.

Abstract: A fastener providing protection against damage to an aircraft resulting from lightning strikes includes an elongated shaft having a head disposed at an upper end thereof, one, the other, or both of the shaft and the head containing a circumferential groove disposed proximate an intersection of the shaft and the head, a lower surface of the head including a plurality of grooves extending radially outward from the circumferential groove and terminating at an outer periphery of the lower surface. A tubular sleeve is disposed concentrically about the shaft and has a plurality of through-slots disposed therein. Each through-slot has a lower end disposed above a lower end of the sleeve, and an upper end disposed in fluid communication with the circumferential groove, such that superheated gases and particles generated in interfaces between the fastener and the adjacent skin due to lightning strikes are vented harmlessly to the atmosphere through the channels and grooves.

Abstract: Described herein is an apparatus for applying and curing a light-curable material on a work surface. The apparatus includes a nozzle from which the light-curable material is applied to the work surface to form a layer of light-curable material on the work surface. The layer of light-curable material has a leading edge and a trailing edge defined according to a direction of movement of the nozzle relative to the work surface. The apparatus also includes a light source fixed relative to the nozzle. The light source is operable to direct a light beam to the trailing edge of the layer of light-curable material.

Abstract: A fastener providing protection against damage to an aircraft resulting from lightning strikes includes an elongated shaft having a head disposed at an upper end thereof, one, the other, or both of the shaft and the head containing a circumferential groove disposed proximate an intersection of the shaft and the head, a lower surface of the head including a plurality of grooves extending radially outward from the circumferential groove and terminating at an outer periphery of the lower surface. A tubular sleeve is disposed concentrically about the shaft and has a plurality of through-slots disposed therein. Each through-slot has a lower end disposed above a lower end of the sleeve, and an upper end disposed in fluid communication with the circumferential groove, such that superheated gases and particles generated in interfaces between the fastener and the adjacent skin due to lightning strikes are vented harmlessly to the atmosphere through the channels and grooves.

Abstract: A low viscosity polysulfide sealant composition. The composition comprises a curable polysulfide polymer; a crosslinking agent; and a plurality of core-shell particles. The core-shell particles comprise: a core comprising a ferromagnetic material; and a shell comprising silica treated with an organic sulfur containing compound. The shell is capable of bonding with the polysulfide polymer.

Abstract: Methods for making and curing resin-based adhesives are disclosed using encapsulated amine accelerators activated by providing ultrasonic energy.

Abstract: A structural assembly of an aircraft which includes a structural element constructed of a composite material which includes a matrix material and plurality of fibers positioned to extend through the matrix material, wherein at least a portion of the plurality of fibers are accessible from a surface of the structural element. A fastener secures the structural element to a structural component. A metal structure comprising gallium is positioned in contact with a surface of the fastener. The metal structure extends from the surface of the fastener and contacts at least a portion of the at least a portion of the plurality of fibers. Also included is a method for assembling a structure.

Abstract: Cured flexible sealant may be removed from a substrate if the cured flexible sealant includes within its volume a susceptor such as metal susceptor particles. Removal proceeds by exposing the sealant with the susceptor to radio-frequency radiation sufficient to cause dielectric heating in the susceptor. The consequent heating in the cured sealant reduces the bond strength of the cured sealant. The reduced bond-strength sealant may be removed by physical methods, such as scraping etc., much more easily than the original (unexposed) cured sealant. Also disclosed are sealant compositions with susceptor, susceptor tools to introduce susceptor into cured sealant, and handheld radio-frequency heaters to apply radio-frequency radiation to cured sealant.

Abstract: Cured sealant may be removed from a substrate if the cured sealant includes a susceptor within its volume. Removal proceeds by exposing the sealant with the susceptor to radio-frequency radiation sufficient to cause dielectric heating in the susceptor and the consequent heating in the cured sealant reduces the bond strength of the cured sealant. The reduced bond-strength sealant may be removed by physical methods, such as scraping etc., much more easily than the original (unexposed) cured sealant. Also disclosed are sealant compositions with susceptor, susceptor tools to introduce susceptor into cured sealant, and handheld radio-frequency heaters to apply radio-frequency radiation to cured sealant.

Abstract: Cured sealant may be removed from a substrate if the cured sealant includes a susceptor within its volume. Removal proceeds by exposing the sealant with the susceptor to radio-frequency radiation sufficient to cause dielectric heating in the susceptor and the consequent heating in the cured sealant reduces the bond strength of the cured sealant. The reduced bond-strength sealant may be removed by physical methods, such as scraping etc., much more easily than the original (unexposed) cured sealant. Also disclosed are sealant compositions with susceptor, susceptor tools to introduce susceptor into cured sealant, and handheld radio-frequency heaters to apply radio-frequency radiation to cured sealant.

Abstract: A lightning-protected conductive composite fuel tank includes a conductive material arrayed on an outer surface to at least partially cover a fastener centerline. Through holes extend along the fastener centerline through the conductive material and the underlying fuel tank shell. These through holes are countersunk into the fuel tank shell to a depth such that a fastener in a through hole will avoid electrical continuity or communication with the conductive material on the fuel tank outer surface. The gap in the countersunk through holes, between the fastener heads and the coextensive outer surface of the fuel tank, is filled with a dielectric or nonconductive material.

Abstract: An apparatus comprises a wall, an internal structure, and a fastener. The wall has a conductive surface and a countersunk hole. The countersunk hole passes through the internal structure. The fastener has an interference fit within the countersunk hole.

Abstract: A lightning-protected conductive composite fuel tank includes a conductive material arrayed on an outer surface to at least partially cover a fastener centerline. Through holes extend along the fastener centerline through the conductive material and the underlying fuel tank shell. These through holes are countersunk into the fuel tank shell to a depth such that a fastener in a through hole will avoid electrical continuity or communication with the conductive material on the fuel tank outer surface. The gap in the countersunk through holes, between the fastener heads and the coextensive outer surface of the fuel tank, is filled with a dielectric or nonconductive material.

Abstract: A lightning-protected conductive composite fuel tank includes a conductive material arrayed on an outer surface to at least partially cover a fastener centerline. Through holes extend along the fastener centerline through the conductive material and the underlying fuel tank shell. These through holes are countersunk into the fuel tank shell to a depth such that a fastener in a through hole will avoid electrical continuity or communication with the conductive material on the fuel tank outer surface. The gap in the countersunk through holes, between the fastener heads and the coextensive outer surface of the fuel tank, is filled with a dielectric or nonconductive material.

Abstract: An apparatus comprises a wall, an internal structure, and a fastener. The wall has a conductive surface and a countersunk hole. The countersunk hole passes through the internal structure. The fastener has an interference fit within the countersunk hole.