Estimation of Notched Composite Plates Fatigue Life Using Residual Strength Model Calibrated by Step-Wise Tests

Abstract

The proposed new technique of fatigue life prediction for notched composite plates is based on a residual strength model calibrated with the use of step-wise fatigue tests. It was proposed to calibrate the fatigue model with fatigue tests in which load conditions are in a step-wise fashion. The adopted fatigue model takes into account the most important loading parameters such as testing frequency, stress ratio, layer orientation and maximal fatigue stress. It was demonstrated that with the use of step-wise fatigue tests, it is possible to calibrate the fatigue model for a particular material and structure with the use of fewer samples. In the experimental tensile and fatigue tests TVR 380 M12/26%/R-glass/epoxy composite plates [+45°/−45°]4 with circular and elliptical cut-outs were used. The fatigue tests were performed under different loading conditions. The influence of testing frequency, stress ratio, maximal fatigue load and also geometry of the cut-out on damage growth rate and fatigue life were studied. The predicted fatigue life was in good agreement with the durability determined experimentally in all investigated samples.

Application of DIC Method in the Analysis of Stress Concentration and Plastic Zone Development Problems

“…The cutouts of various shapes, such as circular, rectangular, triangular, etc., often occur in the structural elements [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 32 ]. They may be used to reduce the weight of the object or to provide access to a certain part of the device or structure during its operation.…”

“…On the other hand, machine or structure design for several years has become a compromise between the cost and time spent on designing. The contemporary designed structural machine elements are increasingly complex and may include certain shape modifications, e.g., holes or openings [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ]; grooves, shoulders, and undercuts [ 26 , 27 , 28 , 29 , 30 , 31 ]; threads [ 10 ]; keyways [ 9 ]; welded connections [ 13 , 32 ]; etc. Such disturbance of the geometry disrupts the flow of the internal forces and causes the local high-stress occurrence, which is sometimes several times higher than the nominal stress calculated with simple basic formulas [ 33 , 34 , 35 ].…”

The Thickness Effect of PSF Nanofibrous Mat on Fracture Toughness of Carbon/Epoxy Laminates

“…Carbon fiber-reinforced polymers (CFRPs) are among the most common composite laminates used in different industries, especially in the automotive and aerospace industries. Despite their advantages, such as a high specific strength and elastic modulus, they can be easily damaged under fatigue, impact, or other loading [1][2][3][4]. The main damage modes of composite laminates are matrix cracking, fiber breakage, matrix/fiber deboning, and delamination.…”

Experimental and FEM Studies on Secondary Co-Curing Reinforcement of Laminates

“…The geometry of the holes is small relative to the overall size. Results of static and fatigue tensile tests for composite laminates with large cut-outs have been reported in the literature [13,14]. Vinayak et al [13] have carried out experimental studies on the fatigue behavior of laminated composites with a circular hole under in-plane uniaxial random loading, and the degradation of material strength as a function of applied number of cycles.…”

“…Vinayak et al [13] have carried out experimental studies on the fatigue behavior of laminated composites with a circular hole under in-plane uniaxial random loading, and the degradation of material strength as a function of applied number of cycles. Romanowicz et al [14] have given a fatigue life prediction method for notched composite plates based on a residual strength model calibrated with the use of step-wise fatigue tests. The maximum buckling load can be increased by approximately 1.5 (depending on cut-out size and reinforcement type) of a simply supported panel with reinforcement rings on both sides, but reinforcement form of only one side does not increase buckling stability [15].…”