THERMAL CONDUCTIVITY CHARACTERIZATION OF A CFRP SINGLE-LAP JOINT

Kurzfassung

Fiber reinforced plastics (FRP), especially Carbon-FRPs, are a frequently used material for spacecraft’s primary and secondary structural design. Optimal results are achieved when the distinctive orthotropic mechanical properties are considered in the composite structures’ design process. Besides their excellent mechanical properties, FRPs offer also a high potential for thermal applications. In order to allow a partially coupled analysis, Lange [1] proposed a semi-analytic formula which connects the structural and thermal analysis of loadbearing single-lap joints (SLJ). For its validation, a thermal vacuum test was conducted [1] which showed non-conclusive results. The present paper presents shortcomings identified in [1] and how they are resolved. Next to improvements on the setup an additional experiment on material basis was conducted. It not only allowed the precise confirmation of the calculated CFRP material’s thermal conductivity lamda_11, but also to validate the whole setup for the SLJ experiment. The latest test results revealed that after the implemented setup changes and even though the temperature gradients are strictly limited, the experiment is very sensitive to radiation effects. This is shown by an analytical approximation of the radiative heat loss from the specimen to the environment and comparing it to the experimental results. [1] M. Lange, V. Baturkin, C. Hühne, O. Mierheim (2018). Validation of an analytical model describing the heat flux distribution in load-bearing CFRP single-lap joints_v1. In Proc. of 15th European Conference on Spacecraft Structures, Materials & Environmental Testing, Noordwijk, The Netherlands.