The inhomogeneity of the local stiffness and strength of a composite based on glass mat

Composite plates based on randomly oriented short fibers are widely use as construction material because of its manufacturability and isotropy of mechanical properties in the plane of the plate. However a significant inhomogeneity of the short fibers distribution makes to use the additional safety factor, which depends on the variation coefficient of local strength characteristics. In this paper, the object of study is fiberglass, produced by the method of the contact molding in which the filler - four layers of glass mat Ahlstrom M-600 (the length of fiber 50 mm), and the matrix - polyester binder resin Polylite 440-M850 and catalyst Butanox M50. Standard methods for studying the inhomogeneity of the mechanical properties require the use of large samples for tensile tests (width of not less than 50 mm, length 500 mm, - a few dozen) that does not give correct information on the distribution of local strength. In a study done by the fundamental assumption that the local stiffness and strength in the plane of the plate is linearly related to the volume content of filler, therefore, with stiffness in the transverse direction, the study is available for non-destructive testing - indentation. We obtain a map of the distribution of transverse stiffness and the statistical characteristics - the average stiffness and coefficient of variation. Mathematical modeling of the distribution of values of transverse stiffness possible to determine the dependence of the coefficient of variation, and the volume fraction of glass fibers for plates made of mats, with an arbitrary surface density. The dependence of the coefficient of variation of the number of layers in the composite