Effect of the Matrix on the Properties of Carbon Fiber Reinforced Plastics

The effect of rigid and flexible matrices on the properties of carbon fiber reinforced plastics has been studied using the impact break method at different rates of loading the composite material (CM). It has been established that the strain of CM under static loading conditions has a smooth character and is generally tensile. For this reason, CM with a plastic matrix under static loading conditions has higher properties, such as the maximum specific absorbed-in-fracture energy alpha = 154 J/cm(2) and the maximum strength sigma = 524 MPa at a greater relative strain epsilon = 6%. The fracture mechanism of carbon fiber reinforced plastics (CFRPs) abruptly changes upon an impact. The fracture of CMs is initiated by an impact at the first moment of its action. The entire process of CM strain until fracture is accompanied by fiber filament breaks. Load fluctuations occur due to filament breaks and are reflected in the strain curves in the form of peaks. The processes of filament break and crush are superimposed on the overall process of multistage CM tensile strain at a higher level. The accumulation of fiber crushes and breaks decreases the strength of CMs. This leads to fast fracture at lower strain in comparison with the case of static loading conditions. The specific absorbed-in-fracture energy alpha of CFRPs with a flexible matrix decreases upon an impact by a factor of 3.4, from 154 to 45 J/cm(2), relative to the specific absorbed-in-fracture energy of CM in the static case; the material is fractured at a smaller relative strain epsilon = 1.7% and a lower strength sigma = 496 MPa.