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PROCEEDINGS OF THE ELEVENTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING
Edited by: B.H.V. Topping
Measurement of Diffuse Damage due to Environmental Stress in Polymer Matrix Composites Laminates
M. Gigliotti and A. Riccio
Laboratory for Computational Mechanics, Centro Italiano Ricerche Aerospaziali C.I.R.A., Capua, Italy
M. Gigliotti, A. Riccio, "Measurement of Diffuse Damage due to Environmental Stress in Polymer Matrix Composites Laminates", in B.H.V. Topping, (Editor), "Proceedings of the Eleventh International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 123, 2007. doi:10.4203/ccp.86.123
Keywords: environmental loading, damage mechanics, micromechanics, homogenisation techniques.
Environmental stress and cycling exposure to aggressive environment may promote damage in composite materials, in the form of fibre-matrix debonding, matrix microcracks, delamination. The first two scenarios of damage are sometimes referred as diffuse damage, this term means that this kind of damage is almost uniformly spread over wide portions of material. Experimental evidence of diffuse damage in polymer matrix composites subjected to mechanical and thermal loading has been provided in the literature [1,2,3].
From the modelling point of view, much effort has been put to an accurate mechanical description of diffuse damage in composites, by means of Continuum Damage Mechanics (CDM) , Shear-Lag (SL) , Micromechanics (MM)  and Finite Element Model (FEM) approaches. However, much is still lacking about the accurate modelling of long-term degradation-damage progression due to realistic environmental effects.
The present paper proposes a mixed theoretical-experimental methodology to assess damage development and progression in polymer matrix composites. The methodology consists in employing 0/90 unsymmetric samples for the continuous monitoring of the degradation mechanisms due to the environment.
The modelling approach is characterised by the employment of micromechanical models based on previous work by Kachanov  together with irreversible evolution laws. These models are specialised for composite plates under hygrothermal bending and are able to simulate the irreversible curvature evolution of 0/90 composite plates under environmental loads.
In detail, first, the elasto-fragile behaviour of 0/90 unsymmetric samples under environmental loadings is modelled by employing an explicit damage ply law based on micromechanics models and homogenisation based techniques. The model is then employed to simulate the response of the samples under complex environmental test conditions.
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