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Objective of the investigations is the determination of the dynamic fatigue behaviour of sheet moulding compounds (SMC) by the application of a very precise hysteresis measur ing method. The influence of material composition such as glass content, amount of filler, resin toughness, etc. on the dynamic fatigue behaviour of R-SMC is of special interest.

Thermoelastic stress analysis (TSA) is a powerful technique to measure the temperature changes induced in a cyclically loaded material. For a quantitative analysis of the strain field from the measured temperature change a calibration of the measured TSA-signal is necessary. In the calibration of the fibre-reinforced materials, the anisotropic and inhomogeneous nature of the material has to be taken into account. The measured TSA-signal is usually provided in camera units (CUs). To calibrate the thermoelastic signal against the material's physical properties, a temperature calibration of the TSA-signal has to be performed. This is achieved using DeltaVision software by assigning the measured CUs to a temperature value, taking the infrared sensor's non-linear response into account.A calibration is conducted against a measurement on uniaxially loaded specimens with respect to the observed material's microstructure and its resulting mechanical and thermoelastic properties. The calibration constant evaluated is compared with a calibration against the material's physical properties and applied to a component under a working load.From the measurement results, it appears that the influence of the middle stress predicted by the higher-order theory of the thermoelastic effect is significant for the investigated material.

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