A micro-mechanics perspective to the invariant-based approach to stiffness

Journal article (2019)

Authors

A. Arteiro Universidade do Porto
M.A. Bessa (OLD) MSE-5
C. Furtado Universidade do Porto
PP Camanho Universidade do Porto, INEGI
Research Group
(OLD) MSE-5
A. Polymer-matrix composites (PMCs) C. Micro-mechanics A. Laminate C. Elastic properties C. Laminate theory
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Published Date

2019

Language

English

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Research Group

(OLD) MSE-5

Abstract

To simplify the analysis and characterisation of composite laminates, an invariant-based approach to stiffness that takes the trace of the plane stress stiffness matrix as a material property was recently proposed. In the present work, a study based on micro-mechanical models brings new insight to this invariant-based approach. The Rule of Mixtures and the Halpin-Tsai models are used to establish the relations between the fibre volume fraction, the fibre/matrix stiffness ratios, and the trace-normalised engineering constants of unidirectional laminae and multidirectional laminates. For sufficiently high longitudinal fibre/matrix stiffness ratios and for fibre volume fractions between 50% and 70%, typical of advanced CFRPs, the variation of the trace-normalised longitudinal Young's modulus is within 6% for unidirectional laminae and within 1% for multidirectional laminates, supporting the definition of an invariant-based approach to stiffness based on a Master Ply concept and laminate factors derived thereof, defining clearly a domain of applicability of the invariant theory and confirming the empirical observations of the past.