Brittle fracture of the reinforced composite element has been a matter of considerable concern to engineers for many years. It is now generally accepted that the mode of failure is the centerpiece of the problem. The publication presents the experimental and numerical procedure used to determine the state of' the stress in the photoelastic model of reinforced beams. The fracture process of fiber reinforced composite materials is very complicated, and the fracture strength is affected by: matrix cracking, fiber breakage and interfacial debonding between matrix and fibers. The criterion used to calculate the maximum load was derived based on two processes only: matrix cracking and deformation of the rei nforcerncnt. The theoretical ultimate bending moment was calculated using the strain energy release rate Ge and the stress intensity factors (K11 and K1) corresponding to the crack propagation of the matrix and the elastic-plastic deformation or the yield limit of the reinforcement.

For an impact fracture test, the influence of Coulomb friction between the specimen and anvil on contact forces and dynamic stress intensity factor (DSIF) has been investigated numerically. It has been shown that friction leads to increasing of the mean tup and anvil forces and decreasing of mean DSIF. Additionally, in most cases, friction leads to increasing of the amplitude of DSIF oscillations and, in consequence, makes interpretation of the test results more complex. Simple formulae for correction of reduced by friction mean DSIF values have been proposed.