FAR-FIELD AND NEAR-FIELD STRAIN RESPONSE OF AUTOMATED TOW-PLACED LAMINATES TO STRESS-CONCENTRATIONS

In this study, the response of laminates with stress concentrations is explored. Automated Tow-Placed (ATP, also known as Fiber-Placement) laminates are compared to conventional tape layup manufacturing. Previous tensile fracture tests on fiber-placed laminates show a 20% improvement in notched tensile fracture compared to tape layup laminates. A hierarchical modeling scheme is presented. In this scheme, a global model is developed for laminates with notches. A local model is developed to study the influence of inhomogeneities at the notch tip, which are a consequence of the fiber-placement manufacturing technique. In addition, a stacked membrane model was developed to study delaminations and splitting on a ply-by-ply basis. The results indicate that some benefit with respect to tensile fracture (up to 11 %) can be gained from inhomogeneity alone, but that the most improvement may be obtained with splitting and delaminations which are more severe in the case of fiber placement compared to tape layup. Improvements up to 36% were found from the model for fiber-placed laminates with damage at the notch tip compared to conventional tape layup.