The Effect of Single Fiber Elastic Modulus Distribution and Modulus Strain Dependency on Carbon Fiber Tow Behavior

摘要

The relation of individual fiber properties to their assemblies, i.e. fiber bundles orrntows, is critical to the predictive performance of fiber reinforced polymer composites.rnStatistical modelling of fiber bundles based on the mechanical behavior of singlernfibers has demonstrated that a large distribution in single fiber failure strength within arntow will lower the tow failure stress, despite equivalency in mean fiber failure stress.rnUsing very precise mechanical testing, it has been shown by the authors that the elasticrnproperties of single PAN carbon fibers within a small fiber tow (12k) have significantrnvariation as well, which has only recently been quantified using a novel nano-tensilerntesting system. In this paper, the tensile behavior of a fiber tow is simulated using thernproperty distributions obtained from single carbon fiber tensile testing, in particularrnthe statistical distribution of axial modulus and the dependency of axial modulus onrnstrain amplitude. Considering identical fiber failure statistics, a 15% reduction in towrnfailure stress was found for a standard deviation in modulus equal to ±8%, a typicalrnvalue experimentally observed by the authors for high performance carbon fibers.rnFurthermore, carbon fiber modulus dependency on strain amplitude reduces towrnstrength if non-uniform fiber loading is considered, indicating that manufacturingrnprocess control of fiber alignment and residual stress is critical to improving thernoverall strength of a polymer reinforced carbon fiber composite.