Development of CFRP Class A body panels and structural components for automotive applications

Abstract

Investigations were completed in two areas of research. Firstly mechanical compression test coupons of unidirectional carbon fibre composite were optimised to produce repeatable and reproducible data to support automotive structural applications. The compressive strength was determined through ASTM D 695 M testing, and the results were correlated with test variations implemented. Various preparation methods were evaluated in the determination of the cause of variation found in unidirectional carbon fibre test specimens. Analytical tools were implemented, including microscopical techniques, Scanning Electron Microscope, Talyscan and X-Ray Tomography to determine initiation of failure and to quantify the damage encountered by the compressive test specimen. The findings correlated well with the mechanical test results, which indicate that the higher quality laminates in terms of surface and edge finishes will have better mechanical properties compared to lower quality composites.

Secondly, the characterisation of the surface of a material designed for automotive body applications. The CBS 95 is manufactured by Gurit UK and has been designed to be the first carbon fibre material to be cured using vacuum bagging and have no evidence of print through at the surface. Various characterisation tools, including Proscan 2000, microscopical techniques, and Dynamic Mechanical Analysis, were used to evaluate anomalies found at the surface of the components manufactured from CBS 95. The origin and formation mechanisms of the anomalies was sought and explained with use of models and the analytical equipment, two main origins were found: porosity and kitting defects. Additionally, the sustainability of CBS 95 exposed to harsh environments was investigated. The CBS 95 was exposed for 20 weeks in three different environments (hot/dry, hot/wet and chemical). Analytical techniques such as MINOLTA Spectrophotometer CM-500 Series, Gloss analyser and microscopical techniques were used to quantify the environmental degradation of the CBS 95. The CBS 95 performed consistently in each of the three environments.

The work has also made many recommendations for improved manufacturing routes for both the compressive test specimen and the CBS 95, reducing processing time and improving quality. These suggestions, when considered together, contribute significantly to carbon fibre manufacturing.

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