FRACTURE TESTING AND ANALYSIS OF ADHESIVELY BONDED JOINTS FOR AUTOMOTIVE APPLICATIONS.

In 1992, the Oak Ridge National Laboratory (ORNL) began a cooperative effort with the Automotive Composites Consortium (ACC) to conduct research and development that would overcome technological hurdles to the adhesive bonding of current and future automotive materials. In accomplishing this mission, the bonding of similar and dissimilar materials was identified as being of primary importance to the automotive industry since this enabling technology would give designers the freedom to choose from an expanded menu of low mass materials for component weight reduction. Early in the project`s conception, five key areas were identified as being of importance to the automotive industry. (1) The development of appropriate methods for determining the properties of the adherends and adhesives independent of one another. (2) The determination of accurate, highly standardized fracture test methods for quantifying, not just qualifying, an adhesive/adherend system`s resistance to crack growth. (3) Modeling of joints so that designers would be able to examine the effects of minor design changes without entering into an expanded testing program. (4) Non-destructive inspection of production bonds either during the bond formation, after adhesive curing or after component completion. (5) Mechanisms for increasing the manufacturability and reducing the production costs of bonded composites. Thismore » paper concentrates on the details of developing accurate fracture test methods for adhesively bonded joints in the automotive industry. The test methods being developed are highly standardized and automated so that industry suppliers will be able to pass on reliable data to automotive designers. Mode I fracture tests have been developed that are user friendly and automated for easy data acquisition, data analysis, test control and repeatability. Also, materials and manufacturing issues are addressed which are of particular importance when designing adhesive and composite material systems.« less