Analyzing the effect of energy dissipation on thermo-mechanical responses of viscoelastic fiber reinforced composites using finite element method

Carbon fiber reinforced composites (CFRCs) are preferred materials used in the aerospace industry for high performance load carrying applications. The polymer matrix in CFRCs is a viscoelastic material and its mechanical properties vary with time, temperature and applied external loads. Experimental work suggests that polymers and polymeric composites, subjected to high-frequency cyclic loading, can generate enormous amount of heat from the energy dissipation which softens the polymer and accelerates failure. Current research efforts on the cyclic response in CFRC focus on understanding the macroscopic (overall) performance of composites, i.e., number of cycles to failure for a given frequency and loading amplitude. A systematic understanding on the formation of heat generation and its effect on the mechanical properties of the constituents in composites, and microscopic responses of composite is currently lacking. Changes in the micromechanical field variables (strain, stress, temperature) of CFRCs during cyclic loading can be crucial in understanding failure in composites. This study attempts to provide a detailed understanding on the effect of energy dissipation due to the viscoelastic nature of polymer on the overall mechanical responses of CFRP composites subjected to cyclic loading. Finite element (FE) analyses on the deformations of CFRP composites under various boundary conditions and loading histories are presented. A thermo-mechanical viscoelastic constitutive model is used for the polymer which is defined using a material subroutine, in ABAQUS FE code. In addition, voids are added to the CFRC models to account for manufacturing imperfections and their influence on the field variables and macroscopic behaviors are investigated.