Dear all,

For my graduation project I am looking into the degradation of flax reinforced epoxy composites, with a bidirectional (5H satin) weaving pattern.

Background

For the mechanical properties I want to add an engineering prediction model so a rough estimate can be made for in the design stage. I found several articles with model mainly based on the rules of mixtures. Most are only applicable to unidirectional composites, however, I have a othotropic (only fibres in two principle directions) or a quasi-isotropic final composite. I found the article ‘Laminate mechanics for balanced woven fabrics’ from Remko Akkerman, which have closed form expressions for quasi-isotropic laminates (see figure for formula). It is unclear for me how the lamina properties are obtained. I have obtained/guessed most of the values of the seperate components. I have the feeling that I’m overlooking something really basic since it is generally not explained in the articles. Simply using the rules of mixtures like it is a unidirectional composite seems wrong.

For the fibres the coordinate system is '1' for the fibre direction and '2' for the radial directions. For the composite the 12 plane is the plane of the composite plate. Direction '3' is the normal of the composite plate. Properties in the '1' and '2' directions are equal.

Question

How do I determine the properties of a lamina (or the whole laminate) with 5-Harness satin weave and epoxy, for both orthotropic and quasi-isotropic laminates?

Thanks in advance for any help you can provide.