## 1 Introduction
### Mechanical Behaviour at Elevated Temperatures  
An understanding of the temperature behaviour of the represented metal-CFRP hybrids and its components is of utmost importance. In experiments, the mechanical behaviour at the temperature levels of 23 \({}^{\circ}\)C and 60 \({}^{\circ}\)C is investigated. Hence, in the following chapter, the temperature behaviour of aluminium, CFRP, and PPA-GF30 is shortly described regarding current literature with focus on this temperature range. Aluminium as a metal exhibits a naturally higher temperature resistance than the PPA-GF30 or the epoxy matrix of the CFRP. The crystalline structure of metals allows much higher temperatures without deforming or degrading the material. Up until 100 \({}^{\circ}\)C, the predominant mechanism of plastic deformation is dislocation gliding. The mechanical properties, whilst static testing, do not change significantly until 100 \({}^{\circ}\)C. The melting point for unalloyed aluminium lies at 660 \({}^{\circ}\)C, whereas the properties in dynamical testing are not examined as much [14]. Since most common matrix materials are thermosets and thermoplastics, the role of the matrix becomes more important when testing CFRP at higher temperatures. For this research, a thermosetting epoxy resin matrix was used. Since thermal and mechanical properties of a polymer rely heavily on process parameters and underlying monomers, this results in a wide range of different polymers which can consist of similar structures. In conclusion, even comparisons in the same polymer class (i.e., epoxy) are difficult to obtain, but compared to the melting point of carbon fibres or aluminium, the epoxy resin softens and finally decomposes at a relatively low temperature. [PERSON] et al. [15] carried out tests on the mechanical behaviour of CFRP at elevated temperatures using rectangularly shaped specimens. A dropdown of the tensile strength to about 68% at 60 \({}^{\circ}\)C was observed when 100% is at 16 \({}^{\circ}\)C, but eventually remaining constant at this level. This leads to the assumption that once the glass transition temperature (T\({}_{\text{g}}\)) of the matrix is exceeded, it contributes less to the tensile strength, hence lowering the tensile strength of the CFRP. This is implied by a comparison of dry carbon fibres which only reach 48% of the tensile strength of the CFRP at 16 \({}^{\circ}\)C. He also detected a change of failure modes for CFRP above 120 \({}^{\circ}\)C [15]. [PERSON] et al. [16] performed three-point bending tests and focused on the influence of temperature changes on the flexural strength and the delaminated area of CFRP with two different matrix types (epoxy and PEEK). It turned out that the delamination area of the CF/EPOX specimens increased inversely proportional to the surface temperature. Conclusive to that, lower temperatures exhibit larger delamination areas [16]. The tensile fatigue life prediction of CFRP was investigated by [PERSON] et al. [17]. They showed that with given stress ratio, frequency, and temperature the tensile fatigue life can be predicted by obtaining a master curve. This prediction method works for satin-woven CFRP laminates as well as unidirectional CFRP [17]. The term PPA-GF30 refers to a fibre reinforced polyphthalamide (PPA). In this case, it is filled with 30 vol.% of cut glass fibres. Generally speaking, the mechanical behaviour of polymers is strongly dependent on temperature, loading frequency and strain rate. Additionally, the tensile strength and stiffness of polymers are much lower than those are for aluminium. In this case, only thermoplastics and thermosets are considered. Thermoplastics melt before decomposing, whereas thermosets just decompose. The polyphthalamides contain an aromatic as well as an aliphatic group, which stabilise them at high temperatures. The heat distortion temperature of this PPA-GF30 with 290 \({}^{\circ}\)C is very high compared to other common used polymers [18].