Multi-Scale Modelling of Long-Term Mechanical Behaviour in Polymer Composite Laminates with Woven Fibre Architecture

Abstract

A comprehensive analytical model for predicting the long-term durability of polymers and polymer matrix composites should in general take into account polymer viscoelastic/viscoplastic creep, hygrothermal effects, and the effects of physical and chemical ageing on material response. These effects, in turn are influenced by a multitude of factors such as polymer morphology, service temperature, ambient relative humidity, internal moisture concentrations, stacking sequence, fibre volume fraction, fibre architecture, applied stress level, degree of damage and ageing time. The primary objective of this paper is to present a multi-scale modelling methodology to simulate the long-term interlaminar properties in polymer matrix woven composites and then predict the critical regions where failure is most likely to occur. A micro-mechanics approach towards modelling the out-of-plane viscoelastic behaviour of a five-harness satin woven-fibre cross-ply composite laminate is presented, taking into consideration the weave architecture and time-dependent effects. In-plane properties are assumed to be dominated by the carbon fibres and are hence deemed elastic. The classical lamination theory model proposed by Raju and Wang is adapted to include the in-plane elastic behaviour of woven fibre composites. For the matrixdominated out-of-plane response, a viscoelastic creep model is employed to model the resin, based on Schapery's nonlinear viscoelastic constitutive law. In addition, physical ageing of the matrix has been included in the model, using the effective time theory proposed by Struik. Furthermore, the effect of large deflections and rotations on the time dependent out-of-plane behaviour is also investigated using the micro-mechanics model. The homogenized in-plane and out-of-plane compliance obtained using the proposed micro-mechanics methodology could be applied within the framework of a structural finite element code to model the macro-scale long-term behaviour of a woven fabric composite structure.

Non-linear Viscoelastic and Physical Ageing Characterisation of Thermoset PR-500 Epoxy Resin

“…In addition, creep and recovery experiments were conducted on un-aged resin specimens in order to characterise the pronounced stress-dependent nonlinear viscoelastic response of the PR500 resin. The resin characterisation data were used in a micromechanics model presented in 1 to predict the matrix dominated out-of-plane response of the graphite/epoxy 5-harness satin weave composite. Figure 6 shows the creep and recovery results at the stress levels of 10, 15, 20, 30, 40 and 50% UTS performed at room temperature.…”

“…Also, the physical ageing characterisation results for a set of temperature and stress conditions are summarised. The properties summarised were successfully used in a multi-scale micromechanical methodology 1 , to study the AS4/PR500 five-harness satin woven-fibre composite laminate. PR500 is the polymer matrix that was modelled using the data presented here.…”