Mechanical Property Study Of CFRP Laminates Subjected To High Impact Compressive Loads

Because of the outstanding mechanical properties, such as light weight, high specific modulus, high specific strength and corrosion resistance and so on, carbon fiber reinforced plastic(CFRP) has been widely used in national defense fields like aviation, aerospace, weapon system and so on. Research about the mechanical response of CFRP material under impact load is a hot issue in this field. Due to the complexity of the problem and the high dispersion of the experimental data, until now, it is still lack of perfect theory to describe the mechanical behavior under dynamic loading conditions, and the damage of composite laminates under high impact load is also lack of experimental data. Based on theoretical study, quasi-static compression and bending experiments and dynamic impact tests, this paper studied the mechanical behavior of CFRP material. The work and main conclusions of this paper are:(1) Based on bridging model, the dynamic constitutive equations and yield criterion containing strain rate effect are adopted to modify the static constitutive equations and yield criterion. The modified model is verified and validated by using some experimental results from relevant literatures, and it can be used in dynamic strength theoretical calculation.(2) Strength of CFRP laminates with different ply angles is studied by using bridging model and quasi-static test method, the influence of different ply angle on the strength of laminates is analyzed. Quasi-static mechanical properties of CFRP material are studied by quasi-static compression tests based on DIC method. The stress-strain curve of test is in agreement with the theoretical calculation results. And the shear strain field obtained by DIC method can reflect the delamination characteristics of laminated composite structure.(3) On the basis of the modified bridging model, the comparison among some structure design schemes are analyzed, and a ply scheme satisfied with use requirements is selected. Samples with this ply scheme are manufactured to conduct medium strain rate compressive tests. The previous theoretical calculation results are consistent with experimental results. Since the experiments can only obtain details like the in-plane strain on the surface and the failure mode, the theoretical calculation program is used to discuss the progressive failure phenomenon, and the relevant mechanical characteristic quantities of fiber breakage and matrix damage are also analyzed.(4) By using digital image correlation method(DIC method), the mechanical properties of CFRP material under quasi-static bending load are studied. The deformation fields obtained by DIC method can effectively reflect the deformation of CFRP material, and DIC method can be used to study different failure modes of CFRP material.