Determination of the shaping behavior of thermoplastic composite materials required for simulation of thermoforming

Abstract

The shaping of composite consolidated plates into products is a complex process. To obtain a defect-free product, we have to bear in mind that thermoplastics reinforced with a fabric practically do not stretch, and their shaping behavior is determined by the mechanisms of shear deformations within a layer or between layers, by the processes of sliding a composite over the surface of tooling and by the flexural rigidity of the consolidated plates. Due to the complex behavior of the material during deformation, the optimization of the thermoforming process by trial and error is rather expensive in implementation and can be successfully replaced by a preliminary simulation. The available software packages intended for modeling the thermoforming process which provide construction of a correct model of the material consistent with the reality, require the introduction of input parameters for the drape of the consolidated plate, its flexural stiffness, the coefficient of friction between layers and with tooling. However, until now there are no standards for their measurement, which significantly hinders the process of modeling the thermoforming of products from consolidated plates based on thermoplastic binders. We present experimental data on the determination of some physical and mechanical properties of carbon fiber reinforced plastics based on polypropylene PP01030, including tensile-displacement tests of the sample, tests with a moving frame that provide evaluating the shear behavior of thermoplastic composite materials, as well as tests for determining the interlayer friction and friction of a composite with tooling. The tests were carried out at the melting temperature of the matrix using specialized tooling, made taking into account the experience of foreign research groups in physical and mechanical testing of thermoplastic composite materials. A method for determining the flexural rigidity of thermoplastic carbon fiber reinforced plastics is proposed. The presented tooling does not require the application of a complex force, and needs only standard tensile test clamps of the testing machine. The data obtained from the physicomechanical tests can be used in virtual modeling of the thermoforming process of consolidated composite plates.