## 4 Conclusions  
Fatigue tests were performed on flax/PLA laminates with different lamina configurations ([0\({}^{\circ}\)]s, [0\({}^{\circ}\)/90\({}^{\circ}\)]s, basket weave, [+45\({}^{\circ}\)/\(-45\)]s, and [90\({}^{\circ}\)]s) with the purpose of determining the fatigue limit using different methods; these are the main conclusions:  
Temperature measurement using infrared thermography is quite sensitive to the environmental temperature variation, especially at low stress applied, where stabilization temperature is below 1.5 \({}^{\circ}\)C; therefore, tests must be performed at different load ratios, which in the end increase the testing cost.  
The Weibull equation fits well to the fatigue life when the load is applied to the fiber direction [0\({}^{\circ}\)]s; however, the estimated fatigue limit is overestimated or even fails to evaluate composites with laminas in different directions; therefore, the Weibull equation should be used with caution.  
Temperature and the maximum strain reach stabilization over 2000 cycles for \(\sigma_{\text{max}}/\sigma_{\text{ut}}<0.7\), which is convenient to evaluate the fatigue limit; furthermore, the use of the thermographic bilinear method to evaluate only the fatigue limit is not recommended, since the results depend on the range of data used to fit both lines, even more so with the high variability of the temperature at low stress applied, which can misinterpret the values obtained.  
According to the results, the volumetric dissipated energy is an alternative, and together with the thermography method, results found can be corroborated, especially at lower stress applied. Furthermore, fatigue limits were found for the studied laminates, showing a low fatigue limit (0.18 to 0.23\(\sigma_{\text{ut}}\)) for laminates with reinforcement in the loading direction, contrary to the rest of the laminates, which show a higher fatigue limit.  
A cyclic stress-strain curve was established based on the strain measurement during the test and fitted to the Ramberg-Osgood model, which can be used to build loading hysteresis.  
The results found in this study can be used to design components where the tensile-tensile cyclic loading is applied; however, the overall mean stress effect is missing. Therefore, future works should focus on the study of composites with different mean stress levels and build the Haigh diagram.  
Conceptualization, S.C. and L.J.-W.; methodology, S.C.; formal analysis, S.C.; investigation, S.C. and D.G.C.; resources, L.J.-W. and C.S.; data curation, D.G.C.; writing--original draft preparation, S.C.; writing--review and editing, S.C., L.J.-W. and C.S.; visualization, L.J.-W.; supervision, C.S.; project administration, C.S.; funding acquisition, C.S. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by Ministerio de Ciencia e Innovacion [AEI/10.13039/501100011033]; and FEDER, Spain, grant number [PID2020-118946 RB-I00] and [TED2021-130314B-I00].  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.  
**Conflicts of Interest:** The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.