The Effect Of Thermal Cycling On The Properties Of A Carbon Fibre Reinforced Aluminum Composite

Continuous carbon fiber-reinforced aluminum alloy composites have shown considerable potential application in field of aerospace engineering due to their high specific strength, high specific stiffness, low thermal expansion coefficient and high thermal conductivity. However, when the composite is applicated in this field, the effect of environment factors in astrospace, especially the therm-cold alternation on the performance of material should be considered.In this paper, M40J/LF6 composites with the volume fraction of 55% was fabricated by a pressure infiltration method and thermal-cold cycling experiment of composites was conducted from -70℃to 120℃or from -196℃to 120℃. Microstructure, mechanical properties and mechanism of fracture of composites after different thermal-cold cycling times were analysed by scanning electron microscopy, transmission electron microscopy, sclerometer and drawing mill.Rare dislocation in the matrix and Al3Mg2 metastablephase and Al58Mg42 phase were observed in annealed M40J/LF6 composite. With the increase of thermal cycling times, micro-crack formed at the interface of carbon fiber and matrix and expanded slowly and finally became invariable.With the increase of thermal cycling times, bending strength of composites showed a fluctuation tendency of first decreasing ,then increasing and finally decreasing, hardness showed a fluctuation tendency of first increasing ,then decreasing and finally increasing and elastic modulus showed a increase of 20% first and then decreased to a stable value of 170GPa.Bending fracture of composites after thermal cycling treatment observed by SEM showed that with the increase of thermal cycling times, amount of pulled fiber tended to increase and finally became invariable. Bonding strength of interface decreased and and finally became invariable with the increase of cycling times.In the process of thermal cycling, microporous and micro-crack formed at partial interface of carbon fiber and matrix due to different thermal expansion coefficient, which resulted in the decrease of strength of composites. Increment of dislocation in the matrix played a important role in the strengthening of composites.