Effect of intra-ply voids on the homogenized behavior of a ply in multidirectional laminates

A Matveeva,L Pyl,L Farkas,M Zhu,R D B Sevenois,W Van Paepegem,D Garoz

doi:10.1088/1757-899x/406/1/012009

Abstract

This work focuses on the effect of intra-ply voids on the homogenized nonlinear behavior of a ply in multidirectional composites. Voids were modeled explicitly on the fiber scale and linked to the ply-scale by the recently developed two-scale framework which couples Classical Laminate Theory on the macro-scale with Finite Element analysis on the micro-scale. Laminates [±45]2s and [±67.5]2s were used as validation cases. The computed homogenized behavior of plies with and without voids for each laminate were compared against existing experimental data on manufactured plates. The nonlinearity of the homogenized stress-strain curves of all models is in a good agreement with experiments up to 1% of applied deformation for a laminate [±45]2s and up to 0.4% for a laminate [±67.5]2s. The effect of voids was assessed only virtually and it is shown that 4% of void content decreases the ply strength by 30%, transversal Young’s and shear moduli by around 10% and 8% respectively, whereas longitudinal stiffness is only slightly affected by the presence of voids. This work is the first step towards automatization of the virtual identification of the complete set of damage-plasticity parameters for the LMT-Cachan damage model accounting for the presence of intra-ply voids.

Highlights

The effect of voids on the mechanical behavior of the fiber reinforced composites, including multidirectional laminates and textile based composites attracts attention of the composite community since many years
To estimate the “as-manufactured” properties of specimens, the SimcenterTM virtual material characterization (VMC) ToolKit was extended with a feature of void generation at the fiber scale together with a special set of loadings and homogenization in order to perform virtual testing on multidirectional laminates
Simulations on the laminates [±45]2s and [±67.5]2s are conducted with and without voids, that are explicitly modeled at the fiber scale with different void type and content

Summary

Introduction

The effect of voids on the mechanical behavior of the fiber reinforced composites, including multidirectional laminates and textile based composites attracts attention of the composite community since many years. The effect of voids on the composite mechanical properties and on the set of parameters for LMT-Cachan model has been investigated in [10]. A clear influence of voids on the damage initiation and propagation and on the parameters of the LMT-Cachan damage model was established Such experimental assessments of the effect of voids is very challenging, especially if to compare the effect against the reference material without voids. In [12] Garoz et al provides a methodology to identify parameters of the LMT-Cachan damage model by means of dedicated micro-mechanical virtual tests with detailed constituent material models, representative geometry and specific load conditions. Micro-mechanical virtual tests on a void-free material were employed with the objective to compare the homogenized behavior of plies in [±45]2s and [±67.5]2s laminates under the static tensile loading against existing experimental data on the laminates. Material properties of the constituents are summarized in table 1

Data used for validation of the macro-scale behavior

Results and discussion

Conclusions and future work