Development of a Methodology for Analysis of Full Field Strains in Thermoplastic Exterior Body Panels Using Photoelastic Techniques

Thermoplastics are rapidly gaining acceptance throughout the automotive industry as an attractive alternative to steel for exterior automotive body panel applications. The transition from steel to thermoplastic is driven primarily by the unique balance of physical properties derived from this new class of engineering polymers. These properties include corrosion resistance, dent resistance and reduced production costs. However, it is recognized that thermoplastic parts must be designed such that the stresses imposed on the component in service are minimized. By minimizing the strain and corresponding stress, the designer could help prevent problems associated with cracking induced by solvents or constraint at the panel attachment locations. This paper proposes a new methodology for analysis of full field stresses in thermoplastic exterior body panels. The methodology utilizes photoelastic stress analysis techniques to define areas of maximum stress in injection molded components. Results of the study are confirmed through conventional electrical resistance strain gage stress analysis techniques.