Strength Criterion Variants for Unidirectional Polymer Composites by the Fracture Condition of the Inter-fibre when there is Compression Perpendicular to the Fibers

When analyzing the strength of structures made of layered fibrous polymer composite materials, the fracture criterion of a monolayer, a unidirectionally reinforced composite is used. In a unidirectional composite, the matrix shearing area makes a dihedral angle with the plane of fibers. This angle increases with an increase in the ratio of transverse compressive and shear stresses. This type of fracture of the binder is the most dangerous and leads to the complete destruction of the composite structure. Linear and quadratic versions of the strength criterion are formulated according to the binder strength condition, taking into account the effect of normal stress on shear resistance, corresponding to the asymmetric friction law. A formula is derived that determines the plane angle of possible fracture. Types of installation tests are considered, and experimental verification of the proposed criteria is carried out.