Abstract: A low-density, halogen-free epoxy composition that is flame-resistant upon curing and is suitable for use as a potting compound. The epoxy composition includes: (a) an epoxy component; (b) at least one curative; (c) at least one latent curing accelerator; (d) a toughening component that includes nano-sized core shell rubber (CSR) particles having particle size of less than 1 micron; (e) a fire-retardant component that is halogen-free; and (f) hollow microspheres for reducing the density of the composition. The fire-retardant component includes a mixture of: (i) at least one polyphosphate; (ii) at least one metal borate; and (iii) at least one compound selected from alkaline earth metal hydroxides and aluminum hydroxides.

Abstract: A multifunctional surfacing material capable of providing lightning strike protection (LSP) and burn-through resistance. In one embodiment, the multifunctional surfacing material is composed of a conductive layer positioned between two resin layers, at least one of which contains one or more fire retardant compounds. In another embodiment, the multifunctional surfacing material is composed of a conductive layer positioned between two resin layers one of which is a thermally-stable layer. The surfacing material is co-curable with a composite substrate, e.g. prepreg or prepreg layup, which contains fiber-reinforced matrix resin.

Abstract: A method for surface preparation of composite substrates prior to adhesive bonding. A curable surface treatment layer containing blocked isocyanate compounds is applied onto a curable composite substrate, followed by co-curing. The surface treatment layer may be a resin layer without fibers or a removal peel ply composed of resin-impregnated fabric. After surface preparation, the composite substrate is provided with a chemically-active, bondable surface that can be adhesively bonded to another composite substrate to form a covalently-bonded structure.

Abstract: A bonding method for joining two structural parts using a curable adhesive layer having a fibrous veil embedded therein. The fibrous veil carries a polymeric binder, which is in a solid phase at room temperature (20° C.-25° C.) and is capable of dissolving into the adhesive composition during curing thereof.

Abstract: A multifunctional surfacing material capable of providing lightning strike protection (LSP) and burn-through resistance. In one embodiment, the multifunctional surfacing material is composed of a conductive layer positioned between two resin layers, at least one of which contains one or more fire retardant compounds. In another embodiment, the multifunctional surfacing material is composed of a conductive layer positioned between two resin layers one of which is a thermally-stable layer. The surfacing material is co-curable with a composite substrate, e.g. prepreg or prepreg layup, which contains fiber-reinforced matrix resin.

Abstract: A low-density, halogen-free epoxy composition that is flame-resistant upon curing and is suitable for use as a potting compound. The epoxy composition includes: (a) an epoxy component; (b) at least one curative; (c) at least one latent curing accelerator; (d) a toughening component that includes nano-sized core shell rubber (CSR) particles having particle size of less than 1 micron; (e) a fire-retardant component that is halogen-free; and (f) hollow microspheres for reducing the density of the composition. The fire-retardant component includes a mixture of: (i) at least one polyphosphate; (ii) at least one metal borate; and (iii) at least one compound selected from alkaline earth metal hydroxides and aluminum hydroxides.

Abstract: A method for surface preparation of a composite substrate prior to adhesive bonding. The surface preparation method includes applying a resin-containing peel ply onto a composite substrate, followed by co-curing. The resin-containing peel ply contains a non-removable textile carrier and a removable woven fabric embedded therein. After co-curing, the peel ply is removed from the composite substrate such that the removable woven fabric is removed but the non-removable textile carrier and a film of residual resin remain on the composite substrate, thereby creating a modified, bondable surface on the composite substrate. The composite substrate with the modified surface can be bonded to another composite substrate, whereby the textile carrier remains an integrated part of the final bonded structure.

Abstract: A method for surface preparation of a composite substrate prior to adhesive bonding. The surface preparation method includes applying a resin-containing peel ply onto a composite substrate, followed by co-curing. The resin-containing peel ply contains a non-removable textile carrier and a removable woven fabric embedded therein. After co-curing, the peel ply is removed from the composite substrate such that the removable woven fabric is removed but the non-removable textile carrier and a film of residual resin remain on the composite substrate, thereby creating a modified, bondable surface on the composite substrate. The composite substrate with the modified surface can be bonded to another composite substrate, whereby the textile carrier remains an integrated part of the final bonded structure.

Abstract: A multifunctional surfacing material capable of providing lightning strike protection (LSP) and burn-through resistance. In one embodiment, the multifunctional surfacing material is composed of a conductive layer positioned between two resin layers, at least one of which contains one or more fire retardant compounds. In another embodiment, the multifunctional surfacing material is composed of a conductive layer positioned between two resin layers one of which is a thermally-stable layer. The surfacing material is co-curable with a composite substrate, e.g. prepreg or prepreg layup, which contains fiber-reinforced matrix resin.

Abstract: A bonding method for joining two structural parts using a curable adhesive layer having a fibrous veil embedded therein. The fibrous veil carries a polymeric binder, which is in a solid phase at room temperature (20° C-25° C.) and is capable of dissolving into the adhesive composition during curing thereof.

Abstract: Peel ply for surface preparation and a method of surface preparation prior to adhesive bonding. A resin-rich peel ply is applied onto a curable, resin-based composite substrate, followed by co-curing. After co-curing, the composite substrate is fully cured but the matrix resin in the peel ply remains partially cured. When the peel ply is removed, a roughened, bondable surface with chemically-active functional groups is revealed. The composite substrate with the chemically-active, bondable surface may be bonded to another composite substrate to form a covalently-bonded structure.

Abstract: A method for surface preparation of composite substrates prior to adhesive bonding. A curable surface treatment layer containing blocked isocyanate compounds is applied onto a curable composite substrate, followed by co-curing. The surface treatment layer may be a resin layer without fibers or a removal peel ply composed of resin-impregnated fabric. After surface preparation, the composite substrate is provided with a chemically-active, bondable surface that can be adhesively bonded to another composite substrate to form a covalently-bonded structure.

Abstract: A method for bonding composite substrates is disclosed. A curable surface treatment layer is applied onto a curable composite substrate, followed by co-curing. After co-curing, the composite substrate is fully cured but the surface treatment layer remains partially cured. The surface treatment layer may be a resin film or a peel ply composed of resin-impregnated fabric. If a peel ply is used, the peel ply is peeled off after co-curing, leaving behind a remaining thin film of partially cured resin. A subsequent dry physical surface treatment, such as plasma, is carried out to physically modify the surface of the surface treatment layer. After dry physical surface treatment, the composite substrate is provided with a chemically-active, bondable surface, which is adhesively bonded to another composite substrate to form a covalently-bonded structure.

Abstract: A method for surface preparation of composite substrates prior to adhesive bonding. A curable surface treatment layer is applied onto a curable, resin-based composite substrate, followed by co-curing. After co-curing, the composite substrate is fully cured but the surface treatment layer remains partially cured. The surface treatment layer may be a resin film or a removal peel ply composed of resin-impregnated fabric. After surface preparation, the composite substrate is provided with a chemically-active, bondable surface that can be adhesively bonded to another composite substrate to form a covalently-bonded structure.

Abstract: A multifunctional surfacing material capable of providing lightning strike protection (LSP) and burn-through resistance. In one embodiment, the multifunctional surfacing material is composed of a conductive layer positioned between two resin layers, at least one of which contains one or more fire retardant compounds. In another embodiment, the multifunctional surfacing material is composed of a conductive layer positioned between two resin layers one of which is a thermally-stable layer. The surfacing material is co-curable with a composite substrate, e.g. prepreg or prepreg layup, which contains fiber-reinforced matrix resin.

Abstract: A method for surface preparation of composite substrates prior to adhesive bonding. A curable surface treatment layer is applied onto a curable, resin-based composite substrate, followed by co-curing. After co-curing, the composite substrate is fully cured but the surface treatment layer remains partially cured. The surface treatment layer may be a resin film or a removal peel ply composed of resin-impregnated fabric. After surface preparation, the composite substrate is provided with a chemically-active, bondable surface that can be adhesively bonded to another composite substrate to form a covalently-bonded structure.

Abstract: A method for surface preparation of composite substrates prior to adhesive bonding. A curable surface treatment layer is applied onto a curable, resin-based composite substrate, followed by co-curing. After co-curing, the composite substrate is fully cured but the surface treatment layer remains partially cured. The surface treatment layer may be a resin film or a removal peel ply composed of resin-impregnated fabric. After surface preparation, the composite substrate is provided with a chemically-active, bondable surface that can be adhesively bonded to another composite substrate to form a covalently-bonded structure.

Abstract: Peel ply for surface preparation and a method of surface preparation prior to adhesive bonding. A resin-rich peel ply is applied onto a curable, resin-based composite substrate, followed by co-curing. After co-curing, the composite substrate is fully cured but the matrix resin in the peel ply remains partially cured. When the peel ply is removed, a roughened, bondable surface with chemically-active functional groups is revealed. The composite substrate with the chemically-active, bondable surface may be bonded to another composite substrate to form a covalently-bonded structure.

Abstract: Peel ply for surface preparation and a method of surface preparation prior to adhesive bonding. A resin-rich peel ply is applied onto a curable, resin-based composite substrate, followed by co-curing. After co-curing, the composite substrate is fully cured but the matrix resin in the peel ply remains partially cured. When the peel ply is removed, a roughened, bondable surface with chemically-active functional groups is revealed. The composite substrate with the chemically-active, bondable surface may be bonded to another composite substrate to form a covalently-bonded structure.

Abstract: A composite bonding process is disclosed. At least one of two curable, resin-based composite substrates is partially cured to a degree of cure of at least 10% but less than 75% of full cure. The composite substrates are then joined to each other with a curable adhesive there between. Co-curing of the joined substrates is carried out to form a bonded composite structure, whereby the adhesive is chemically bonded to and mechanically diffused with the resin matrix of the composite substrates, resulting in a chemically bonded interface between the adhesive and each composite substrate. Furthermore, bonding can occur with the presence of contaminants on the joined surfaces.