On the Rate-dependent Plasticity Modelling of Unidirectional Fibre-reinforced Polymeric Matrix Composites

Abstract

Three different approaches to plasticity are investigated to model the experimentally-observed non-linear behaviour of unidirectional fibre-reinforced polymeric matrix materials. The first and simplest approach consists on assuming independent one-dimensional rate-dependent plasticity on in-plane (12) and through-thickness longitudinal (13) shear components of the Cauchy stress tensor. The second, employs a 3D extension of the plane stress Hill’48 anisotropic plastic surface. The third and the last is formulated as a quadratic yield function inspired by Puck’s fracture initiation criterion. It searches for a plastic localisation plane in which a certain combination of normal and shear stresses is maximum. Numerical simulations are conducted to analyse the off-axis compression behaviour of carbon fibre reinforced epoxy composite under varying loading rates. The afore-mentioned three different approaches are explored with an aim to predict the experimentally-observed non-linear response of such composites. The model parameters are determined using a deterministic inverse modelling strategy employing an iterative domain reduction optimisation technique. As far as the experiments are concerned, the quasi-static and medium rate tests were carried out in universal testing machines, while the experiments at high rate were conducted in a Split Hopkinson Pressure Bar system. The effectiveness in terms of accuracy and robustness of the three approaches are discussed.

A study on the longitudinal compression strength of fibre reinforced composites under uniaxial and off-axis loads using cross-ply laminate specimens

“…Up to 6°, however, there was no noticeable nonlinearity and no signs of damage or fibre rotation in the specimens before the point of failure. In addition, shear stress-strain curves for the same IM7-8552 material in [21,22] show significant nonlinearity starting only after shear stresses of around 60-70 MPa and both the 3 and 6° tests fall below that limit (see Figure 11). Therefore, for these specimens, an accurate estimate of the internal stress state in the longitudinal plies can be obtained using linear CLT, as was done for the uniaxial compression tests in section 3.2, and the use of CP material instead of UD can be considered valid.…”

Analyzing the failure and damage of FRP composite laminates under high strain rates considering visco-plasticity

“…This model is based on a model previously introduced for the plastic behavior of polymer composites [13] . Erice et al [14] compared 3 different approaches to analyze plasticity under rate dependency. The first approach is to incorporate rate dependency just for in-plane shear plasticity, the second one consists in using 3D extension of the plane stress Hill48 anisotropic plastic surface and third is a quadratic yield function inspired by Pucks fracture initiation criterion.…”