Mesoscale modeling of carbon fiber spread tow fabric subjected to in-plane loading

Ultra-light composites have been produced through the spread tow technology. The reason behind the spread tow fabric’s success originates from its unique woven structure. By interlacing wide spread thin flat tapes, instead of regular (and thicker) yarns, a smaller number of interstices are obtained which leads to less crimp and less accumulation of resin pockets and hence increased fiber volume fraction. In addition, straighter fibers and thinner plies are obtained which also contribute to improved mechanical performance in terms of both stiffness and strength. Yet another benefit is that the carbon fiber spread tow fabric composites combine the high performance of pre-impregnated tape-based composites and the high draping ability of woven fabric composites.It has been shown in previous studiesthat for very thin plies, the crack initiation is delayed, and the matrix cracks appear more closely to final failure. This mechanism requires further investigation and understanding. In the current study, a mesoscale finite element model of a carbon fiber spread tow plain woven composite has been realized, which can be used to analyze the effect of ply thicknesses down to 0.04 mm. The model has been used to study the effect of tow thickness and spacing on the stiffness knock down (due to crimp) and on the initial damage development. By applying shifted periodic boundary conditions through the thickness, also the effect of periodic layer shifting can be analyzed without having to discretize and model more than one layer of the composite