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) [4], Shear-Lag (SL) [5], Micromechanics (MM) [6] 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 [7] 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.

1

Garret, K.W., Bailey, J.E. "Multiple Transverse Fracture in 90^o Cross-Ply Laminates of Glass/Fiber Reinforced Polyester", Journal of Material Science, 12: 157-168, 1977. doi:10.1007/BF00738481

2

Lafarie-Frenot, M.C., Rouquie, S. "Influence of Oxidative Environments on Damage in C/Epoxy Laminates Subjected to Thermal Cycling", Composite Science and Technology, 64: 1725-1735, 2004. doi:10.1016/j.compscitech.2004.01.005

3

Gigliotti, M., Molimard, J., Jacquemin, F., Vautrin, A. "On the Nonlinear Deformations of Thin Unsymmetric 0/90 Composite Plates Under Hygrothermal Loads", Composites Part A: Applied Science and Manufacturing, 37: 624-629, 2006. doi:10.1016/j.compositesa.2005.05.003

4

Talreja, R. "A Continuum Damage Mechanics Characterization of Damage in Composite Materials", Proceedings of the Royal Society of London, A399: 195-216, 1985. doi:10.1098/rspa.1985.0055

5

Hashin, Z. "Analysis of Cracked Laminates: A Variational Approach", Mechanics of Materials, 4: 121-136, 1985. doi:10.1016/0167-6636(85)90011-0

6

Allen, D.H., Harris, C.E., Groves, S.E. "A Thermomechanical Constitutive Theory for Elastic Composites with Distributed Damage." Part I: doi:10.1016/0020-7683(87)90107-7 and II: doi:10.1016/0020-7683(87)90108-9 , International Journal of Solids and Structures, 23: 1301-1338, 1987.

7

Kachanov, M., "Elastic Solids with Many Cracks and Related Problems", Advances in Applied Mechanics 30: 259-445, 1993. doi:10.1016/S0065-2156(08)70176-5

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £120 +P&P)