title = "Structural Adhesive Bonding of Metal Assemblies"

content = """
Structural adhesive bonding uses polymer adhesives to join metal components, distributing load over the entire bond area rather than through discrete fastener points. At Ridgecrest Metalworks, adhesive bonding is used for joining dissimilar metals (where welding is impossible and galvanic isolation is needed), bonding to coated surfaces, vibration damping joints, and hybrid bonded-plus-welded or bonded-plus-fastened assemblies.

Adhesive types used for structural metal bonding include epoxies, acrylics (methacrylate adhesives), polyurethanes, and cyanoacrylates. Two-part epoxies are the most common structural adhesives: they cure at room temperature by mixing a resin with a hardener, developing high shear and peel strength. One-part epoxies require oven cure (250–350°F) and provide higher strength and better elevated-temperature performance. Acrylic structural adhesives (such as methyl methacrylate, MMA) cure quickly at room temperature and can bond to oily or lightly contaminated surfaces. Polyurethane adhesives provide flexibility and impact resistance—used where joint deflection must be accommodated.

Surface preparation is the single most critical factor in adhesive bond strength and durability. Metal surfaces must be chemically clean, slightly roughened, and free from oxide and release agent. Preparation methods include: solvent wiping (acetone, MEK) to remove oil and grease; mechanical abrasion (sanding, grit blasting) to increase surface area and remove weak oxide layers; acid etching or chromate conversion coating (for aluminum) to produce a thin, chemically active oxide layer that bonds well and resists moisture; and plasma treatment for difficult-to-bond metals. Adhesive must be applied promptly after surface preparation before re-contamination occurs.

Bond line thickness must be controlled: most structural adhesives have an optimum thickness of 0.005–0.020 inch (0.1–0.5 mm). Excessive thickness reduces joint stiffness and strength; too thin a bond line leads to voids and incomplete coverage. Spacer beads, shim foils, or part geometry (designed-in stand-off features) maintain correct bond line thickness.

Adhesively bonded joints are strong in shear and tension but relatively weak in peel (cleavage). Joint design must minimize peel loading. Bond-line integrity is checked by tap testing (audible tone change over disbonds), ultrasonic inspection for critical applications, and destructive pull/shear testing on process qualification specimens.
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version = "0.0.1"
