GMW 14892 Adhesion Requirements for Glued Internal Parts

The “GMW 14892 Adhesion requirements for glued internal parts” standard developed by General Motors describes the adhesion requirements for internally bonded parts.

In addition to these requirements, all bonded internal parts must also meet the requirements of the “GMW14444 Material-related internal part performance” standard.

This standard applies to all internally adhesive-joined materials and components. For emblems, the "GMW 16742 Adhesion performance of decorative emblems and nameplates" standard applies.

Suppliers are responsible for evaluating adhesive bonds to ensure that the adhesive bonds comply with the requirements of this specification.

All tests must be performed in an accredited laboratory. Testing facilities and equipment must be in good working order and have a valid calibration label. Alternative testing facilities and equipment may also be used. However, all measurement variables specified in this standard must be determined accurately according to their physical definitions.

Equipment used in the tests includes:

• universal tensile testing machine
• An oven that can maintain a temperature of 105 degrees
• A freezer that can maintain temperatures below minus 30 degrees
• A compartment that can maintain at least 40 percent relative humidity at 95 degrees

In the tests, bonded adhesives prepared in the laboratory using materials for the production purpose or bonded adhesives prepared from produced bonded assemblies are used. At least three samples are evaluated in all tests (peel adhesion, edge adhesion, impact test and dead load test).

In the standard, the testing period is determined as follows: calendar time 10 days, testing time 7 hours and coordination time 1 hour.

When preparing samples, bonded test samples must be completed on production substrates for all visual and mechanical evaluation tests. Pooled test samples are conditioned for 3221 hours in accordance with Code A as defined in GMW 72 prior to exposure to the environment unless otherwise specified. Parts are connected using manufacturing fixtures and tools.

All test pieces are evaluated visually according to the table in the standard:

• The parts must not show any color transfer, bubble formation or delamination (separation of composite layers) after being subjected to dimensional stability testing in accordance with the dimensional stability and natural weather conditions in the GMW 14444 standard.
• In terms of edge adhesion, the parts are fixed to represent the in-car position. There should be no visual loss of adhesion such as peeling, lifting and unwrapping of edge wraps after exposure to one of the environmental effects specified in the standard.
• For mechanical evaluation, if one or both of the adhesives are flexible, a peel test is performed. If both adhesives are hard, coupon and part level testing is performed. In the peel test, at least three samples are tested for each adhesion test. Each test specimen must be at least 25 mm wide and 150 mm long. Peel adhesion test is performed according to ISO 8510-2 standard. The test specimens are subjected to peel testing at a 300-degree angle at a constant jaw separation speed of 180 mm/min. Peel adhesion tests should be completed at the temperature of the specified test specimens after removal from environmental exposures.
• If it is not possible to perform 180-degree peel adhesion tests on samples taken from the parts due to geometry, the ends of the adhesives are glued with a fixing mechanism to enable the adhesives to be tested at 180 degrees. Peel adhesion tests are performed on the samples taken after each of the environmental exposures (at least 72 hours after adhesive application).

Adhesive failure is the absence of adhesive in one of the two adhesives after the peel adhesion test. Adhesion failure of the adhesive is the presence of adhesive on both adhesives. Bonding or substrate failure is the presence of more than 70 percent adherent material on one side of the bond line area or a complete stock break failure of a bonded part during testing. Adhesion or substrate failure should be visible to the naked eye without the aid of a magnifying glass or microscope.

Among the numerous testing, measurement, analysis and evaluation studies provided to businesses by our organization, there are also testing services in accordance with the "GMW 14892 Adhesion requirements for glued internal parts" standard.