The effects of hygrothermal ageing on the fatigue properties of a unidirectional glass/epoxy composite have been investigated. Damage nucleation was monitored in terms of fibre breakage by in-situ microscopic observation of the tensile face of the specimens during flexural tests. From the mapping of individual fibre breaks during monotonic and fatigue loading, the overall losses of properties were linked to the drop in the glass fibres’ load-bearing properties. The endurance properties of the composite declined after water ageing. A drop in the in-situ statistical distribution of fibre strengths could account for such an observation. Furthermore, this fibre weakening was associated with an increase in the pH of the ageing media. During water sorption, the water gradually becomes alkaline due to leaching and the hydrolysis of the matrix's unreacted hardener.
Get full access to this article
View all access options for this article.
References
1.
IshaiO., Environmental Effects on Deformation, 'Strength and Degradation of Unidirectional Glass-Fibre Reinforced Plastics’, Polymer Engineering and Science, 15, 7 (1975) 491.
2.
BlagaA., ‘Water Sorption Characteristics of GRP Composite: Effect of Outdoor Weathering’, Polym. Comp., 2, 1 (1981) 13.
3.
ApicellaA. and NicolaisL., ‘Effect of Water on the Properties of Epoxy Matrix and Composites’, Adv. Polym. Sci., 72 (1985) 69.
4.
CollingsT.A., HarveyR.J. and DalzielA.W., ‘The Use of Elevated Temperature in the Structural Testing of FRP Components for Simulating the Effects of Hot and Wet Environmental Exposure’, Composites, 24, 8 (1993) 625.
MengesG. and GitshnerH.W., ‘Sorption Behaviour of Glass-Fibre Reinforced Composites and the Influence of Diffusing Media on Deformation and Failure Behaviour’, Proc. of Third Int. Conf. Comp. Mat. (ICCM/3), A.R Bunsell Ed., Pergamon, Oxford, U.K., 3, (1980) 25.
7.
MikolsW.J., SeferisJ.C., ApicellaA. and NicolaisL., ‘Evaluation of Structural Changes in Epoxy Systems by Moisture Sorption-Desorption and Dynamical Mechanical Studies’, Polym. Comp., 3, 3 (1982) 118.
8.
EllisT.S. and KarashF.E., ‘Interaction of Epoxy Resins with Water: the Depression of Glass Transition Temperature’, Polymer, 25 (1984) 664.
9.
PerezJ., MuzeauT. and CavailleJ.Y., ‘α and β Mechanical Relaxations in Amorphous Polymers. Rubber-Glass Transition and Physical Ageing’, Plastics, Rubber and Comp. Processing & Appl., 18 (1992) 139.
10.
ChateauminoisA., ChabertB., SoulierJ.P. and VincentL., ‘Dynamic Mechanical Analysis of Epoxy Composites Plasticized by Water: Artifact & Reality’, Polym. Comp., 16, 4 (1995) 288.
11.
ZhouJ. and LucasJ.P., ‘The Effects of a Water Environment on Anomalous Absorption Behaviour in Graphite-Epoxy Composites’, Comp. Sci. & Tech., 53 (1995) 57.
12.
JonesF.R. and MulheronM., The Effect of Moisture on the Thermal Expansion Behaviour and Thermal Strains in GRP’, Composites, 14, 3 (1983) 281.
13.
SubramaniamN., BlumF.D. and DharaniL.R., ‘Effects of Moisture and Other Contaminants in Friction Composites’, Polym. Eng. & Sci., 33, 18, (1993) 1204.
14.
CharlesR.J., ‘Static Fatigue of Glass’, J. Appl. Physics, 19, 11 (1958) 1549.
15.
MetcalfeA.G., SchmitzG.K., ‘Mechanism of stress corrosion in E-glass fibres’, Glass Technology, 13, 1, (1972) 5.
16.
MazerJ.J. and WaltherJ.V., ‘Dissolution Kinetics of Silica Glass as a Function of pH between 40°C and 85°C, J. of Non-Cryst. Sol., 170, (1994) 32.
17.
ChamisC.C. and SinclairJ.H., ‘Durability/Life of Fibre Composites in Hygrothermomechanical Environments’, Comp. Mat.: Testing & Design (Sixth Conference), ASTMSTP787, DanielI.M., Ed., American Society for Testing and Materials, (1982) 498.
18.
JonesC. J., DicksonR.F., AdamT., ReiterH. and HarrisB., ‘The Environmental Fatigue Behaviour of Reinforced Plastics’, Proc. R. Soc. Lond., A396, (1984) 315.
19.
FrenchM.A., PritchardG., ‘Environmental stress corrosion of hybrid fibre composites’, Composites Science and Technology, 45 (1992) 257.
20.
BrownR.P., ‘Durability of Polymers - Material Property Data’, Polym. Testing, 12 (1993) 423.
21.
ChateauminoisA., ChabertB., SoulierJ.P. and VincentL., ‘Hygrothermal Ageing Effects on the Static Fatigue of a Glass-Epoxy Composites’, Composites, 24, 7 (1993) 547.
22.
ChateauminoisA., ChabertB., SoulierJ.P., VincentL., ‘Long time ageing of glass-epoxy composites’, Proc. Int. Symp. “Textiles in Building Construction”, HamelinP. and VercheryG. Ed., Pluralis, Paris, Part 3 (1990) 155.
23.
JonesF.R., ShahM.A., BaderM.G., BonifaceL., ‘The Analysis of Residual DICY and amide and its Effect on the Performance of GRP in Water and Humid Environments’, Sixth Int. Conf. on Comp. Mat. (ICCM/6), 4, Ed. by MatthewsF.L., Elsevier Applied Science., London & N.Y. (1987) 4.443.
24.
HagnauerG.L. and DunnD.A., ‘Dicyandiamide Analysis and Solubility in Epoxy Resins’, J. Appl. Polym. Sci., 26 (1981) 1837.
25.
GalyJ., PhD Thesis, Institut National des Sciences Appliquees de Lyon (1985).
26.
KasturiarachchiK.A. and PritchardG., ‘Free Dicyandiamide in Crosslinked Epoxy Resins’, J. Mater. Sci., Letters, 3 (1984) 283.
27.
KasturiarachchiK.A. and PritchardG., ‘Scanning Electron Microscopy of Epoxy-Glass Laminates Exposed to Humid Conditions’, J. Mater. Sci., 20 (1985) 2038.
28.
BrockmanW., HennemannO-D., KollekH. and MateC., ‘Adhesion in Bonded Aluminium Joints for Aircraft Construction’, Int. J. Adhesion & Adhesives, 6, 3 (1986) 115.
29.
HöhneL. and UllnerC., ‘Modelling of Time Strength Behaviour of Soda-Lime-Silica Glass in Moist Environment’, Glass Sci. Tech., 67, 8 (1994) 220.
