In this study the effect of basalt and carbon fiber content on
IntroductionPerformance improvement is one of the most important criteria when a novel polymer composite is developed for engineering applications. For the optimal mechanical performance of materials composite industry uses several types of reinforcing materials [1]. The popularity of glass fibers is unbroken, but nowadays carbon fiber is gathering ground, thanks to its decreasing price and well known good mechanical properties [2][3][4]. Another competitor is basalt fiber. Its composition is close to glass fiber, but this eruptive rock has less complex structure, its thermal and chemical resistance is much better and production is simpler compared to widely used E-glass fiber [5,6]. As well as glass fibers basalt fibers appeared not only as reinforcement of polymer matrices but also in concretes [7,8].Because of the high performance and the mass production the fiber reinforced plastics are becoming increasingly popular in the automotive industry. These composites usually suffer fatigue load, that is why it is important to investigate the fatigue properties of a new type of composite. More and more researchers assume that not just the fatigue life of a material is important but also the failure process itself, therefore researchers pay more attention to the investigation of fatigue crack propagation and failure analysis [9][10][11][12][13][14]. Esmaelliou et al. [14] investigated the fatigue properties of glass fiber reinforced polyamide 66, where the load factor which is the ratio of minimal and maximal stress was 0.1 and frequency was 20 Hz. They showed that the fatigue process during loading of polyamide 66 can be divided into three parts. In the first part the relative Young's modulus decreases intensively and temperature increases gradually. Then in the second part, both the temperature and the relative modulus are approximately constant. The third part begins typically when 75% of the number of cycles that belongs to failure is reached. In this part temperature increases and relative modulus decreases again until failure. At higher load levels the second and the third part become less remarkable and gradually disappear by further load increment.There are only a few publication that deals with the investigation of fatigue properties of injection molded thermoplastic