Diese Website verwendet Cookies. Mit der Nutzung der Website stimmen Sie deren Verwendung zu. Weitere Informationen erhalten Sie in unserer Datenschutzerklärung.

The influence of ondulation in fabric reinforced composites on dynamic properties in a mesoscopic scale

Structural mechanic properties of fiber reinforced plastics depend on the single components’ properties, namely matrix and fiber. Simple Micromechanical homogenization theories reach a limit when a laminate consists of fabric reinforced layers instead of unidirectional layers. The ondulations of warp and fill yarn caused by the textile semi-finished product are the reason why the mesoscopic dimension, lying between the microscopic and the macroscopic dimension, has to be taken into account when mechanically characterizing fabric reinforced composites. A one-dimensional mathematical model is formulated in order to obtain a representative sequence of one complete ondulation. Because of the ondulation the total deformation is presumed to consist of the mechanical strain and additionally a purely geometrical deformation that contributes to the total deformation behavior. A theoretical approach for a correlation between the degree of ondulation and the material’s geometrical contribution to deformation is carried out. The aforementioned mathematical model is the basis for the following finite-element-analysis. As a first step the obtained results are compared with existing representative volume elements implemented in LS-DYNA. Their suitability for modeling the above described behavior is evaluated. Especially when considering structural dynamic properties there often is only moderate compliance between theoretically based finite-element-models and experimentally determined values for the damping behavior. The investigation focuses on the material model *MAT_234 already implemented in the LS-DYNA material library. It includes a representative volume element considering the geometry of ondulations in fabrics on mesoscopic scale. A solution for the combination of the fabric reinforcement with a matrix component based on the material model *MAT_234 and its adequacy for the prediction of the material’s damping behavior are examined. Finally the finite-element-model is validated by experimentally determined values. Therefore the structural dynamic properties of a free-vibrating cantilever specimen with selected layups are measured with a laser vibrometer.