Self-healing composite roofing sheet with vascular healing network

Abstract

A self-healing composite roofing tile consisting of stacked layers of bio-based fiber reinforcement impregnated with a thermosetting resin matrix, a vascular healing network of borosilicate glass tubes filled with a curing agent / solvent system located between the middle layers, and catalyst-treated intermediate layers adjacent to the tubes, wherein the laminate cures under low load at room temperature to form an integrated roofing tile configured to heal cracks following breakage of the tubes and release of the agent itself.

Description

AREA OF INVENTION

[0001] The invention relates to fiber-reinforced composite roof products with embedded healing channels and catalyst interfaces for autonomous repair of cracks, restoration of performance and extension of service life in building envelopes. BACKGROUND OF THE INVENTION

[0002] Self-healing polymer composites reduce maintenance by releasing curative agents into cracks, where they polymerize and bond damaged surfaces. This is achieved either through microcapsules or vascular channels that store monomers and curing agents and release them upon damage. Capsule-based systems disperse microcapsules and catalysts in resin matrices, while vascular approaches embed hollow fibers or glass capillaries that transport larger volumes and allow for repeated healing cycles. This is suitable for structural laminates such as roofing panels. By embedding glass capillaries or hollow fibers filled with epoxy resins or other monomers and introducing catalysts into adjacent matrix layers, capillary flow and in-situ polymerization are triggered upon crack formation. This results in a significant restoration of toughness and stiffness in fiber-reinforced laminates over multiple cycles.A roof panel that integrates bio-based fiber reinforcement, a thermoset matrix and strategically placed borosilicate glass tubes as vessel reservoirs with catalyst-coated intermediate layers offers durable and repeatable self-healing under operational cracks and environmental influences. SUMMARY OF THE INVENTION

[0003] The invention relates to a composite roof panel consisting of stacked layers of bio-based fiber reinforcement impregnated with a thermosetting resin matrix, a vascular healing network of borosilicate glass tubes filled with a curing agent / solvent system in predefined ratios, and catalyst-treated intermediate layers adjacent to the tubes that initiate polymerization upon release. The layers are arranged such that the initial matrix-wetted layers surround the glass tubes placed between the middle layers and coated with a catalyst-solvent solution. The remaining fiber layers are stacked on top, and the assembly cures under low load at ambient conditions to form a solidified laminate with embedded curing depots.When a crack propagates through a tube, the healing agent penetrates the damaged area via capillary action and hardens upon contact with dispersed or interface-based catalyst. This seals the crack and restores mechanical integrity. The vascular arrangement allows for multiple healing cycles during operation. DETAILED DESCRIPTION

[0004] The roofing membrane consists of several layers of bio-based fibers (e.g., flax, jute, hemp) cut to predetermined sizes and orientations to balance stiffness and adaptability. These are stacked on a laminating machine and impregnated with a thermosetting resin system (e.g., epoxy or bio-epoxy resin) mixed with its hardener to form the matrix material. During the initial application, the first two layers are coated to anchor the vessel elements. Borosilicate glass tubes with selected inner diameters are pre-filled under vacuum with a self-healing agent-solvent mixture in a predefined ratio optimized for viscosity, processing time, and polymerization kinetics. The tube ends are sealed to secure the contents until breakage during operation.The filled glass tubes are positioned between the middle fiber layers along expected crack paths or orthogonal grids to increase the probability of trapping. Adjacent fiber interlayers are coated with a catalyst-solvent solution compatible with the self-healing chemistry, so that contact between the released solvent and the catalyst triggers rapid curing at room temperature. The remaining fiber layers are stacked to enclose the vessel network. The laminate assembly is consolidated under a light, uniform load or using a vacuum bag method at room temperature for a specific duration sufficient to achieve complete matrix curing without damaging the glass tubes. Low-temperature curing preserves the integrity of the tubes and the activity of the catalyst.The resulting laminate features continuous vessel channels embedded within the matrix / fiber architecture, with the orientation of the tubes aligned to the stress fields of the roof structure. The outer surfaces can be finished with UV-resistant gelcoats or coatings to protect the matrix from weathering while simultaneously allowing for the repair of subsurface cracks. During operation, capillary action draws the repair compound into the crack as it crosses a tube. Diffusion into the catalyst-treated interlayers or contact with dispersed catalyst sites leads to in-situ polymerization, bonding the crack surfaces and restoring stiffness and fracture toughness, as demonstrated in vessel and hollow fiber systems in fiber-reinforced composites.The borosilicate glass composition of the tubes ensures chemical compatibility, thermal stability, and resistance to the environmental conditions typical of roof applications. Tube diameter and spacing optimize the ratio between structural load and healing reservoir capacity, based on previous vessel design studies. Alternative designs utilize hollow glass fibers or polymer capillaries instead of individual tubes and employ core-sheath nanofibers or microcapsules as additional healing reservoirs in matrix-rich areas to extend healing coverage. Catalyst distribution can be interfacial or particulate, depending on the desired activation kinetics. Manufacturing options include infusion or hand lamination with controlled resin viscosity and degassing to prevent air entrapment around the tubes.The end seals are designed to preferentially fail under critical stress energy release, so that the release of the sealant coincides with the formation of significant cracks rather than harmless microcracks. The architecture allows for multiple healing cycles from the remaining reservoir volume and can be combined with integrated structural monitoring sensors to record healing processes and remaining reservoir capacity throughout the roof's lifetime.

Claims

[1] A self-healing composite roofing tile consisting of stacked layers of bio-based fiber reinforcement impregnated with a thermosetting resin matrix, a vascular healing network of borosilicate glass tubes filled with a curing agent / solvent system located between the middle layers, and catalyst-treated interlayers adjacent to the tubes, wherein the laminate cures under low load at room temperature to form an integrated roofing tile configured to heal cracks after breakage of the tubes and release of the agent itself. [2] Composite roof panel according to claim 1, wherein the borosilicate glass tubes are vacuum-filled and sealed prior to insertion and are arranged along the expected crack paths to maximize the probability of interception while maintaining the stiffness and strength of the laminate suitable for use on roofs. [3] Composite roof panel according to claim 1 or 2, wherein the catalyst-solvent coating is applied to the intermediate layers surrounding the tubes in order to initiate the polymerization of the curing agent at ambient temperature upon release into a crack plane and thus restore stiffness and fracture strength over several cycles. [4] Composite roof panel according to one of the preceding claims, wherein the outer surface comprises a UV-resistant coating and the vascular network is supplemented by microcapsules or core-shell nanofibers dispersed in matrix-rich areas to enhance the healing coverage and capacity.