The effect of long-term ultraviolet light irradiation on polymer matrix composites

The use of aircraft structural parts made of polymer matrix composites subjected to severe environment conditions calls for better knowledge of their long – term behaviour, with an emphasis on their ability to withstand important cyclic variations of moisture and temperature. The influence of temperature and moisture on such structures is receiving special attention, because it induces transient residual stresses within the plies. Such stresses must be taken into account in the design of composite materials, particularly aerospace structures, e.g. aircraft. In the present paper the transient hygroscopic stresses induced by cyclic and unsymmetric environmental loadings which simulate an aeronautical application are investigated. It is shown that the heterogeneity and anisotropy of such plates generally result in transient stress distributions which are very different from the equilibrium stress distribution. Some stacking sequences exhibit important stresses within the plies. These stresses have to be taken into account in the design of composite structures submitted to a moist environment.

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Effects of physical aging on long term creep of polymers and polymer matrix composites

International Journal of Solids and Structures ◽

10.1016/0020-7683(94)00163-q ◽

1995 ◽

Vol 32 (6-7) ◽

pp. 827-846 ◽

Cited By ~ 97

Author(s):

L. Catherine Brinson ◽

Tom S. Gates

Keyword(s):

Polymer Matrix ◽

Physical Aging ◽

Polymer Matrix Composites ◽

Matrix Composites ◽

Term Creep

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Application of the Electronic Speckle Pattern Interferometry (ESPI) Technique for the Localisation Analysis of Damage Development in Composites

Nondestructive Evaluation ◽

10.1115/imece2002-33448 ◽

2002 ◽

Author(s):

Pascal J. P. Bouquet ◽

Albert H. Cardon

Keyword(s):

Polymer Matrix ◽

Polymer Matrix Composites ◽

Electronic Speckle Pattern Interferometry ◽

Strength Analysis ◽

Creep Recovery ◽

Matrix Composites ◽

Damage Development ◽

Damage Initiation ◽

Delayed Failure

The analysis of the long-term behaviour of polymer matrix composites has to be performed for their stiffness evolution and for their strength changes. Long fiber reinforced polymer matrix composites exhibit an anisotropic viscoelastic-viscoplastic behaviour. The non-linear viscoelastic constitutive equations proposed by R. Schapery [1], with a viscoplastic correction are able to analyse the long-term stiffness evolution on the basis of some short-term creep and creep-recovery tests. For the strength analysis it is possible to consider some delayed failure approach as the end of a viscoelastic-viscoplastic behaviour. The experimental follow-up of the creep evolution till rupture needs a full field technique in order to have a complete view of the strain field and the evolution of this field where the damage initiation and development transforms the homogeneous strain distribution in an heterogeneous one. The ESPI technique shows clearly the location of the damage initiation and allows us to follow the damage development. Examples of the ESPI technique on graphite epoxy specimen will be presented and the results in relation to the delayed failure analysis will be discussed.

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Long-term Water-aging of Whisker-reinforced Polymer-Matrix Composites

Journal of Dental Research ◽

10.1177/154405910308200111 ◽

2003 ◽

Vol 82 (1) ◽

pp. 48-52 ◽

Cited By ~ 25

Author(s):

H.H.K. Xu

Keyword(s):

Polymer Matrix ◽

Polymer Matrix Composites ◽

Matrix Composites ◽

Nano Indentation ◽

Water Exposure ◽

Reinforced Polymer ◽

Aging Resistance ◽

Sic Whiskers

Long-term water exposure may degrade polymer-matrix composites. This study investigated the water-aging of whisker composites. It was hypothesized that whiskers would provide stable and substantial reinforcement, and that whisker type would affect water-aging resistance. Silica-fused Si3N4 and SiC whiskers were incorporated into a resin. The specimens were tested by three-point flexure and nano-indentation vs. water-aging for 1 to 730 days. After 730 days, SiC composite had a strength (mean ± SD; n = 6) of 185 ± 33 MPa, similar to 146 ± 44 MPa for Si3N4 composite (p = 0.064); both were significantly higher than 67 ± 23 MPa for an inlay/onlay control (p < 0.001). Compared with 1 day, the strength of the SiC composite showed no decrease, while that of the Si3N4 composite decreased. The decrease was due to whisker weakening rather than to resin degradation or interface breakdown. Whisker composites also had higher moduli than the controls. In conclusion, silica-fused whiskers bonded to polymer matrix and resisted long-term water attack, resulting in much stronger composites than the controls after water-aging.

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