Electromagnetic modeling of composite panels as planar multilayers involving a periodic set of circular cylindrical fibers in each constitutive layer is considered. As a first step, the case of a single layer is studied. Combining multipole method and plane-wave expansion leads to full-wave field representations in all space, yielding in particular reflection and transmission coefficients for TE/TM oblique plane-wave illuminations. Gaussian beams are accounted for via a Fourier transform and numerical quadrature scheme. Comparisons with data available for photonic crystals show the accuracy of the method, while results for fiber-reinforced composites illustrate its effectiveness.