Abstract: The moisture absorption curve of a plain weave composite was measured experimentally, and a moisture-absorbing finite element model containing the plain weave microstructure was established. Through this model, the effects of random offset, the angle ratio of the laminate lay-up and the fiber volume in the fiber bundle on moisture absorption were studied. The investigation shows that the moisture absorption behavior of the plain weave composite laminate is in accordance with Fick's law in general. The FEA results agrees well with the test. A random offset of the layup position has an effect on the balanced moisture content. The angle ratio of composite lay-up has a slight effect on the balanced moisture content, but it has no significant effect on the exposure time before banlance.The fiber content in the fiber bundle of plain weave composite material increases, which makes it easier to reach the moisture absorption balance, but the equilibrium moisture absorption rate and the moisture absorption rate decrease.

Key words: plain weave composites, mass diffusion, Fick's law, lamina offset, lay-up ratio, composites