Finite Element Based Degradation Model for Composites with Transverse Matrix Cracks

Abstract

A degradation model for predicting the effective homogenized threedimensional elastic constants of an interior ply with transverse matrix cracks was developed by analyzing a three-ply representative volume element using the finite element method. The degradation model was first evaluated by comparing the homogenized extensional modulus for a cracked [0/(90)3]s laminate with experimental results and finite element discrete models in which each crack was modeled discretely. Further, using the degradation model, the prediction of load redistribution for a cantilevered laminated plate with matrix cracks subjected to transverse end load was compared with a discrete crack model. Also, the prediction of load redistribution in a cracked plain weave composite subjected to uniaxial stress was compared with a discrete crack model. The degradation model showed good agreement in predicting the homogenized elastic constants and load redistributions.

Progressive failure analysis of 2×2 braided composites exhibiting multiscale heterogeneity

“…Specifically, the degradation factors are chosen based on micromechanics analysis of nonwoven laminates containing discretely modeled transverse matrix cracks [27]. When the finite element method is used for the progressive failure analysis, the damage is predicted at each quadrature point in the material coordinate system.…”

Effect of Various Parameters on the Effective Properties of a Cracked Ply

“…It has been observed that when transverse matrix cracks (TMC) form, only the diagonal terms in the compliance matrix change [9]. Laws et al [7] used the self-consistent scheme to calculate the compliance matrix of cracked unidirectional composites.…”

“…Therefore, if ·s i Ò is held constant during crack formation, is also constant. The volume averaged strains ·e i Ò include contributions from the material and the crack faces, as shown below (9) where CS denotes the crack surface. The term can be expressed in terms of ·s i Ò as follows 700 JAE NOH AND JOHN WHITCOMB Again, the formation of cracks does not affect S ij .…”

“…Determination of the degradation behavior of the individual cracked ply was presented in References [7,8] in which, however, the effect of adjacent ply properties and initial properties of a cracked ply on degradation behavior were not examined. A finite element based degradation model was presented in Reference [9] to predict the full three-dimensional effective elastic constants of a cracked ply as a function of crack density. The authors investigated the sensitivity of these constants to the crack density and adjacent ply properties.…”

“…In this paper, as an extension of the work in Reference [9], a wider range of material systems are considered and relationships that describe how initial properties of a cracked ply and the properties of the adjacent plies affect the effective properties of a cracked ply were obtained. These relationships are then used to explain the degradation behaviors of the homogeneous and hybrid laminates for various material systems with different damage states and adjacent ply orientations.…”