# A Model to Study the Creep Behavior of Carbon Fiber/Epoxy Resin Composites Under Temperature
## 3 Materials and Methods
### Experimental Background  
The following describes the facility used to obtain experimental data giving useful results in the modeling performed. There were fifteen single-loop test stations and seven double-loop test stations with slope ratios of 10:1 and 25:1, respectively (Figure 1), in the creep testing facility employed in this study (see [14]). Under computer control, testing can be performed concurrently at all stations. While the latter have a robust working capacity of 30 kN, each lever station has a maximum working load capacity of 6 kN. The loading lever mechanism has three bearing locations. In essence, when the initial position is altered, all of these positions need to align in order to preserve a constant leverage ratio. To reduce friction, caution must also be used when selecting the type of bearing. Electronically, the samples' load level is ascertained. The axial load on the test piece can be linked to the lever's bending through the Wheatstone bridge's output when a single-lever station is used, for instance, and strain gauges are positioned to form a complete bridge. To perform the measurements, we used common bonded strain gauges and a Hottinger Baldwin Messtechnik Quantum X data acquisition system. To experimentally assess how a viscoelastic material responds to prolonged stress circumstances, numerous specimens may need to be tested simultaneously under various loading scenarios. Isothermal testing of a number of previously introduced laminate systems at room temperature and at higher temperatures was part of the current study's test schedule. Tests of room temperature and humidity were conducted at 23 \({}^{\circ}\)C and normal humidity levels. The sophisticated technology in the lab allowed for the consistent performance of creep testing. In experiments, we used [\(\pm\)45]\({}_{25}\) laminates. After adjusting and controlling the room's relative humidity, it was discovered to be within \(\pm\)5% RH. In experiments, we respected the standards DIN EN ISO 8044 [53] and DIN 50125 [54] (for the dimensions of the specimens). The material underwent 10 h of laboratory testing to determine material properties like creep compliance. Because of the restricted experimental options, it is almost impossible to forecast the material's mechanical behavior over longer time periods, like years or even decades, without this information. It is important to perform experiments as accurately as possible since the outcomes of these short-term tests can be used to forecast long-term behavior using a variety of characterization techniques, including the time-temperature overlap principle stated earlier. The strain gauges above the specimen's neutral axis stretch when the device is loaded, while the gauges below it compress in response to the applied stress. For the two-lever loading method, the applied sample force is measured in a somewhat different but fundamentally comparable way. The strain gauge is held in place on the specimen by two spring camps, while the initial length is established prior to the test starting. The sample is elongated when the load is applied because the extensometers on the outside of the platelets are compressed and those on the inside are proportionately stretched. The amount of strain induced in the sample can be ascertained by recording the electrical signal known as UB that is produced as a result. As previously noted, extensometers were used to detect Epsilon axial strain, whereas a traditional strain gauge was used to measure Epsilon transverse strain on the \(\pm\)45 laminates. Figure 1: The single-loop test station and double-loop test station. The shunt calibration method was used for transverse calibration. This effect need not be taken into consideration in axial strain measurements, in which the strain gauges are connected to create a full bridge circuit. Cylindrical heating chambers were installed in several test stations for testing at higher temperatures. The hot oil is regulated by a thermostat and pumped through a copper coil that circles each chamber.