Fracture energy for orthogonal cutting in unidirectional CFRP at different cutting directions

A unidirectional carbon fibre reinforced polymer (CFRP) laminate is a composite material made up of strong parallel carbon fibres incorporated in a polymer matrix such as epoxy to provide high stiffness and strength in the fibre direction of the laminate. Unfortunately, the interlaminar or intralaminar plane of this material has a low resistance to damages as the fracture toughness of a unidirectional CFRP laminate is related to the energy dissipation during the orthogonal cutting. The aim of this study is on cutting a unidirectional CFRP along the longitudinal or transverse directions, characterizing orthogonal cutting forces and the related fracture energy. Orthogonal cutting is performed using braised carbide tools for a range of cutting depth of 10-100 ³m with a rake angle of 30° to quantify the cutting forces and to observe the fracture mechanisms. The fibre orientations have a significant impact on surface bouncing-back. For some fibre orientations, the energy balance model is applicable, deducting the reasonable value of fracture toughness due to high normal force (F t). Fibre subsurface damage and cutting forces during cutting are found to be strongly influenced by the cutting depth. The input energy of cutting is released in form of new surface energy, fibre breakage, high bending energy, and chip fracture energy.

Influence of Stacking Sequence on Strength and Stability of Suspension System Control arm CFRP Laminate Rods

The paper deals with buckling and strength analysis of suspension system rods made of carbon fibre reinforced polymer (CFRP) laminate. The whole suspension system of urban solar vehicle, Eagle Two, designed by Lodz University of Technology students was considered. The calculations and analysis focused on suspension rods, where the traditional metal material was replaced with CFRP laminate. The influence of layer arrangement on rod strength, static, and dynamic buckling were analysed. The research was conducted using numerical simulations employing finite element method software. The static and dynamic load was considered. The obtained results show that the plies’ order in the laminate influences both the strength and stiffness of the considered rod. The best results considering both failure force and longitudinal elasticity modulus were obtained for the stacking sequences with axially oriented (0°) plies on the outside of the rod.

Mechanical Behavior of Active and Passive Strain Sections in CFRP Laminate under Uniaxial Tension

This study investigates the nonlinear behavior of quasi-isotropic CFRP laminate under uniaxial tension. To verify the convergence of the calculated and experimental deviations, the approximating nonlinear equations describing the upper and lower hysteresis loop branches were found. The formation of a hysteresis loop in the active and passive strain sections in CFRP laminate has been studied. The open hysteresis loop development stages are shown from maximum expansion to stabilization, and to the tendency of branches to connect and narrow the loop. The point of the maximum angle between the upper and lower branches of the loop is determined – the apex of the hysteresis loop at maximum deformation. The strain region is found, in which the branches of the loop are parallel. The equations are determined, describing the nonlinear behavior of modules of Ex(ε) in the sections of increasing and decreasing strain. The dependence between mechanical energy dissipation per unit volume and strain was obtained.