In the paper, a detailed experimental and numerical investigation of compression after impact (CAI) behavior of hygrothermal aged T300 985LV carbon/ epoxy composites is presented. Rectangular fabric laminates are damaged by low-velocity impact, and moisture absorption conditioning is carried out. The moisture absorption curves agree with Fick's law, with a moisture equilibrium rate of 0.84% at 1392 h. Then, CAI experiments are carried out on moisture saturated specimens at different temperatures. The effects of hygrothermal environments on CAI strength are obtained with an interpretation of corresponding mechanism. Furthermore, finite element analysis based on hygrothermal mechanics formulation and incremental Newton-Raphson mixed iteration equation is established. The numerical results are in good agreement with the experimental ones, with an accuracy of up to 92%, which demonstrates the effectiveness of the established numerical model. The results show that the CAI strength of 85 RH% hygroscopic saturated laminates is decreased by approximately 12% at 85 C and 17% at 128 C. Additionally, the allowable compression value of 3546 μϵ is obtained for T300 985LV composite laminates, which is useful for applications in civil aircraft design.
K E Y W O R D Scompression after impact, finite element analysis, hygrothermal aged, impact damage, moisture absorption
| INTRODUCTIONCarbon fiber reinforced plastic (CFRP) is widely used in aerospace, marine and other engineering industries. [1,2] Compared with conventional materials, CFRP is characterized by the advantages of high specific strength, high specific stiffness, and excellent fatigue characteristics. [3][4][5][6][7] The percentage of CFRP used in civil aircraft ranges from 25% for the A380 to 50% for the later B787, which indicates that the usage of composite is increasing in primary components for aircraft structures. [8] Since the environment that the composite structure is exposed to significantly affect its performance, it must be accounted for during design. The most important aspect of the CFRP is temperature and moisture (hygrothermal), [9][10][11][12] which are crucial for understanding these effects and considering them in composite design. In addition, the impact damage is another factor that significantly affects composite properties. The impacts (i.e., tool drop, runway gravel, and hail) cause through-thickness stress waves in
