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RESEARCH PRODUCT

Moisture Absorption Effects on the Resistance to Interlaminar Fracture of Woven Glass/Epoxy Composite Laminates

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The influence of moisture absorption on the interlaminar fracture behaviour of 8/8 harness satin weave glass/epoxy composite was investigated. Two series of specimens with 0°/0° and 90°/90° predominant interfaces immersed in water for different duration were tested under double cantilever beam (DCB mode I), single leg bending (SLB mode I + II) and end notched flexural (ENF mode II) loadings. In general, the apparent flexural modulus: E, and the fracture toughness: G C, decrease with increasing moisture content. This effect is more remarkable if mode II participation is bigger. The value of G C measured on 90°/90° specimens reveals higher than that on 0°/0° ones, but the variation in G C is inversed under ENF loading. The experimental results have been correlated with a criterion previously proposed by the first author expressed by: \( G_{TC} = G_{IC} + (G_{IIC} - G_{IC} )\left( {\frac{{G_{II} }}{{G_{I} + G_{II} }}} \right)^{m}.\) A good agreement is shown with m = 2/3 at all moisture contents and interfaces. Regarding the R-curves under DCB loading, water absorption leads to a higher rate of increment in the resistance in the early crack growth. However, the maximum of the resistance to the crack growth decreases with the moisture content.