The physicomechanical and thermophysical properties of phenocarbon plastics based on UVIS carbon fabric were determined. It was found that use of UVIS carbon fabric ensures a high level of performance characteristics of the phenocarbon plastics. Phenocarbon plastics with a 60 wt. % degree of filling with 10 × 10 to 20 × 20 mm reinforcing elements have optimum strength and thermophysical properties with a random scheme of reinforcement.Carbon fibre materials (CFM) are the most promising reinforcing filler for polymer construction materials (PCM). Their manufacture is constantly increasing, the assortment is expanding, and the technologies are being improved [1][2][3][4]. The possibility of using them for reinforcing a wide spectrum of matrices, including polymeric thermosetting matrices, is one of the advantages of CFM [5][6][7][8][9].We investigated the physicomechanical and thermophysical properties of carbon-fibre-reinforced plastics based on phenolformaldehyde binder (LBS-1 bakelite lac, 57.8% dry residue) randomly reinforced with UVIS carbon fabric cut into 5 × 5, 10 × 10, and 20 × 20 mm squares. The samples were prepared for the tests by direct molding of phenocarbon prepregs at 433 K and 20-25 MPa specific pressure followed by heat treatment at 393 K for 4 h.The physicomechanical tests of the carbon-fibre-filled plastics were conducted on standard samples according to GOST for plastics. The thermal stability of the material was determined with the Martens method on a Thurluger WPM VEB instrument, the impact strength was determined with the Sharpy method on a KM-5T impact tester, and the breaking stress and relative compressive strain was determined on a FP-100 testing machine. The flexure tests were performed on a FP-10 universal testing machine.The thermophysical characteristics of the phenocarbon plastic were determined with IT-S-400 (the specific heat capacity in the 323-573 K temperature region) and ITEM-1M instruments (thermal conductivity).The thermal conductivity of the samples was calculated with the equationwhere a is the thermal diffusivity, m 2 /sec; λ is the thermal conductivity, W/(m⋅K); C p is the specific heat capacity, kJ/(kg⋅K); ρ is the density of the sample, kg/m 3 .The thermal stability of the samples was investigated with a PaulikPaulikErdey system Q-1500 D derivatograph from the Hungarian company MOM in the 298-1273 K temperature range with an elevation rate of 10°/min and sample weight of 200 mg.To attain the maximum effect of matrix strengthening in a random reinforcement scheme, the effect of the degree of filling and the overall dimensions of the reinforcing element on the properties of the phenocarbon plastic was investigated. The amount of filler in the plastic was varied within the limits of 50-70 wt. %.