Body Structure Adhesive Material Requirements
|Publication Date:||1 December 2018|
Material Description. This standard is intended to cover the material and performance requirements of structural adhesive candidates that are used to bond automotive body substrates.
It is anticipated that assemblies bonded with these types of adhesives will incorporate a mechanical means of attachment (hems, fasteners, and/or welds) to facilitate fixturing prior to cure of the adhesive, generally, in the heat of the paint bake ovens, or in the case of two (2) component adhesives, the assemblies will be held in appropriate fixtures until the adhesive has attained sufficient strength for handling.
It is further anticipated that this specification shall cover ʺtrueʺ structural bonding applications, that is, cases where substrates are joined primarily by adhesives and the joint must maintain an acceptable strength level throughout the life of the vehicle. The adhesives covered by this standard are meant for use in the vehicle assembly plant body shops and are pumpable, other types of adhesive bonding shall be addressed in separate specifications.
Symbols. Not applicable.
Body Structure. For the attachment of body panels, reinforcements, frame members, floor pans, etc., where strength is required to augment welds, or increase vehicle durability and stiffness.
Closure Assemblies. Bonding of hem flanges and/or inner panel reinforcements to provide integrity and ʺlock-upʺ of the hem seam or durability and stiffness of the reinforcement to the inner panel.
Approvals. Adhesive candidates shall not be used for GM production vehicles without full approval by GM Materials Engineering. Full approval is a two (2) step process consisting of first a technical approval and additionally a production approval. Technical approval requires testing to this specification with at least one (1) GM approved production substrate as specified by the approving GM Material Engineer. Adhesives meeting these requirements shall be listed as "Approved" in the GM Materials Approved Source List. Adhesives can only be used in production (Production Approval) when there is an accompanying "AAA" number, that is an approved adhesive application (AAA) number for the intended application. The AAA number will require testing to this specification for each unique combination of substrates plus surface treatment, etc., intended to be used in vehicle production, or as specified by the approving material engineer. The AAA number can be used as surrogate for multiple bond joint configurations or multiple assembly plant locations as determined by the approving GM Materials Engineer.
Test Data Submission. Technical approval and AAA submissions shall be submitted on the standard test data template. Contact the approving GM Materials Engineer for an electronic copy of the standard test data template for submission.
Dispense. The adhesive system must be capable of being metered, mixed and dispensed using current production equipment.
Paint Bake. Adhesives approved to this specification shall be compatible with production paint systems and cannot be adversely affected by paint oven bake schedules.
Sealing. The use of a structural adhesive in an application does not automatically constitute ʺsealingʺ of that application. Each ʺbondʺ application, requiring ʺsealʺ shall be evaluated on a ʺcase by caseʺ basis, by the GM subject matter experts representing sealing and structural bonding disciplines.