Repair Methods for Composites 250
This class covers basic procedures and best practices for repairing composites, as well as the structure of composite laminates and sandwich panels.
Number of Lessons 18
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- Composite Repair in Manufacturing
- Laminate Structure
- Parallel Laminates
- Crossply, Balanced, and Symmetrical Laminates
- Sandwich Panel Structure
- Tools and Supplies
- Safety Precautions
- Damage Assessment and Removal
- Repair Options
- Fill Repairs
- Injection Repairs
- Bonded Repairs
- Bolted Repairs
- Steps for Making a Bolted Repair
- Best Practices for Composite Repair
- Describe the role of composite repair in manufacturing.
- Describe the structure of composite laminates.
- Describe a parallel laminate stacking sequence.
- Distinguish between crossply, balanced, and symmetrical laminate stacking sequences.
- Describe sandwich panel composite structures.
- List the tools and supplies required for basic composite repair.
- Describe basic safety precautions for repairing composites.
- Describe how to assess and remove composite damage.
- Describe the options for composite repair.
- Describe fill repairs to composites.
- Describe injection repairs to composites.
- Describe bonded repairs to composites.
- Describe bolted repairs to composites.
- List the steps for making a bolted repair to a composite part.
- Describe the best practices for repairing composites.
- Describe the steps for finishing repaired composite parts.
The nominal temperature of the air that surrounds devices and systems. When performing repairs on composite parts, work in an area where the ambient temperature is below 90°F (32°C).
A laminate in which the individual plies occur in +/- pairs at various angles except for 0° and 90°. The pairs must be the same thickness but they are not required to be in any particular order.
A type of wood that is lightweight and springy. Balsa wood may be used in the core of a sandwich panel.
A threaded cylindrical device used for fastening parts. Bolts are used in bolted repairs of composites.
A composite repair method in which the damaged area is covered with a titanium plate that is secured to the part with fasteners and screws. Bolted repairs are typically done on thick laminates designed to bear heavier loads.
A composite repair method in which the damaged area is covered with some type of patch. The three basic types of bonded repair are patch repair, scarf repair, and stepped repair.
The bulging, bending, bowing, or kinking of an object as a result of compressive stress. Combining or stacking individual plies together to form a laminate helps to prevent buckling.
A substance that facilitates chemical reactions in another substance. Catalysts are used to promote hardening in resins and gel coatings.
A material made by combining a binding resin with small filaments of solid material. Composites have the strength of metal, the light weight of plastic, and the rigidity of ceramics.
The middle of a sandwich panel composite. Sandwich cores can be made of foam, balsa wood, or honeycomb.
A laminate in which the ply orientations are oriented at right angles to each other, with ply orientations limited to 0° and 90° only. It is usually best to arrange stacking sequences with fibers oriented in different directions.
The separation of the layers in a laminate. Delamination can occur locally, in a small area of the laminate, or it can affect the entire laminate.
The outer skin of a sandwich panel. Also known as face sheet.
The outer skin of a sandwich panel. Also known as face plate.
Reinforcement material made from extremely fine strands of glass. Fiberglass is the most commonly used reinforcement material in composites.
A relatively simple composite repair method in which resin and filler is applied to the damaged area to fill in nicks, scratches, and dents. Fill repairs are used for minor, non-structural damage on laminates, or on the outer skin of a sandwich panel.
A thin, transparent sheet that bonds to a surface. Film adhesive is used in bonded repairs of composites.
Any machining process that surfaces, conditions, edges, cleans, etc. a part or component. Usually the last step after a workpiece is constructed.
The resulting material after mixing a plastic resin with substances that cause the formation of tiny air bubbles in the resin. Foam may be used in the core of a sandwich panel.
The protective outer coating of a composite material. Gel coat requires the addition of a catalyst before applying so that the coating will harden.
Six-sided. Honeycomb cells in a sandwich core may be hexagonal.
A type of sandwich core in which empty cells are separated from each other by a solid wall. Honeycomb cells can be square or hexagonal.
A composite repair method used primarily for delamination. Resin is injected into the delaminated region and pressure is applied to the part.
Located between individual layers of the laminate.
The displacement of plies within a laminate. Combining or stacking individual plies together to form a laminate helps to prevent interlaminar shear.
Located within a ply of the laminate.
An individual layer of the laminate. Also known as a ply.
Two or more layers of fibrous material that have been bonded together for strength. One of the most common reasons for repairing a composite part is damage to the laminate.
The material that binds together the reinforcing fibers of a composite. The matrix is usually a viscous material that hardens to give shape to the composite part and protect the fibers from damage.
The middle layer of the laminate.
Cosmetic damage that is so slight, it does not affect the structural integrity of the composite material and poses no risk of part failure. Negligible damage can be corrected with a simple procedure, such as buffing, or it can be left as is.
Damage that is so extensive, severe, or expensive that the part must be discarded and replaced with another. Damage may also be deemed nonrepairable simply because the repair work is too costly to justify keeping the part.
A fastening device containing a hole and internal threads that mate with a screw or bolt.
A laminate in which all of the layers are oriented so that the fibers are parallel to the direction of the greatest tension. In composite materials, reinforcement fibers provide the greatest strength when they are oriented in the direction of the load.
Another name for the titanium plate used in a bolted repair.
A type of bonded repair in which replacement material is inserted to fill the damaged area and covered with a series of successively larger repair plies.
An undersized hole that holds a screw more securely when the screw is driven into the hole. Pilot holes are used in bolted repairs of composites.
An individual layer of the laminate. Also known as a lamina.
The period of time after mixing during which a resin remains suitable for use. When repairing composites, keep in mind that the pot life of the resin is limited.
A bond that forms between atoms and that involves the exchanging or sharing of electrons. In composites, the primary bond is formed when the composite is originally cured.
The part of the composite that provides strength, stiffness, and the ability to carry a load. In manufacturing, fibers are the most commonly used reinforcement.
Surface damage and structural damage that can be reversed with repairs, and the part restored to acceptable quality and durability levels. Always consult with someone experienced in composite inspection to determine whether the part can or should be repaired.
A substance made from either synthetic or natural polymers and used for composite matrices. In essence, a resin is a polymer that has not been processed into its final form.
A composite structure in which two stiff outer skins are bonded to a relatively thick but lightweight core. Sandwich panels are preferred in applications requiring a structure that is both highly resistant to bending and extremely lightweight.
A type of bonded repair in which the damaged area is sanded to produce a tapering effect. Film adhesive is laid over the damaged area and covered with a series of successively larger repair plies.
Sanding an area of a part to produce a tapering effect. Scarfing is a common way to create a large but visually attractive repair on a composite.
A bond that involves attraction between molecules, but no transfer or sharing of electrons. Secondary bonds are not as strong as primary bonds.
The arrangement of ply orientations within a laminate. The properties of the laminate vary depending on the stacking sequence.
A type of bonded repair in which the damaged area is sanded to resemble a series of steps. Film adhesive is laid over the damaged area and covered with a series of successively larger repair plies.
A laminate in which the layers below the midplane form a mirror image of the stacking sequence of the layers above the midplane. Symmetrical laminates may have an odd number of layers or an even number of layers.
A visual assessment of surface defects on the composite. Visual inspection is one of the most commonly used non-destructive inspection methods for composites.