Compression Fatigue Testing Setups for Composites—A Review

Abstract

Continuous fiber reinforced plastics show major advantages in tensile loading conditions. This is especially true for cyclic loading due to the good fatigue performance provided by glass and carbon fibers. However, it is widely accepted that compressive loading is a critical load case for most composites. For fiber reinforced plastics, this is mostly due to instabilities on different length scales-beginning at the smallest scale with microbuckling of single fibers to instabilities of fiber bundles, namely, fiber kinking, up to global buckling of the hole laminate. The sequence of events is hard to discern for quasi-static testing, and often, it remains unclear as to the cause of failure. This is even more the case for compressive fatigue testing. Different approaches can be found in the literature on how fatigue tests should be performed. A mandatory requirement for reliable design data is tested under conditions found in subsequently manufactured components. Therefore, it is generally sought to prevent the global buckling while allowing for all other damage mechanisms to take place. Two main testing strategies for axially loaded plates or strip-like specimens can be identified to achieve this goal. One common strategy is shortening the gauge length to a value where global buckling occurs after compressive failure. The second approach uses anti-buckling guides to prevent global buckling. These testing strategies are established methods for static compression testing and are sometimes also used for fatigue testing. However, the number of fixtures in both approaches is numerous, and only some of the fixtures are viable for fatigue testing. These generally accepted methods for compression testing are supplemented by different specimen geometries or loading conditions. A generalized overview is given in Figure 1. The aim of this review is to evaluate the applicability of these testing methods in terms of compressive fatigue testing, namely, loading ratios (load ratio R < 0 and R > 1) containing compressive loads. The evaluation is based on the reported use of a test setup or by discussion of pros and cons of setups for quasi-static testing. This approach is necessary, as the number of reported works on compressive fatigue testing is sparse. This review is structured by testing type rather than chronological order. Before evaluating compression testing methods, a quick summary of failure modes observed in static compression testing is given along with the damage progression under compressive fatigue loading. The review of testing methods then starts with axially loaded flat specimens. In the second and third parts, work on bending tests and tubular specimens is reviewed, respectively. 2. Failure Modes 2.1. Compressive Failure Modes in Fiber Reinforced Composites The properties of fiber reinforced plastics depend mainly on the type of reinforcement chosen as well as the stacking sequence of layers within a laminate. For compressive loads, the matrix

Methodology for testing the compressive strength of pultruded composites

“…5 Some researchers have reported compressive testing of composite laminates using different fixtures and anti-buckling arrangements. 6,7…”

“…5 Some researchers have reported compressive testing of composite laminates using different fixtures and anti-buckling arrangements. 6,7 Budiansky and Fleck 8 conducted theoretical and experimental study on the compression failure of carbon and glass composites. The failure mode was found to be plastic kinking of the composite.…”

“…Some researchers have conducted compression testing in bending or tubular arrangement. 7 However, this compromises on the accuracy of the results by introducing non-uniform stress distribution. Some fixtures make use of guidance sleeves to deal with misalignment and buckling issues.…”

“…Some fixtures make use of guidance sleeves to deal with misalignment and buckling issues. 7 The compressive properties are highly sensitive to the manufacturing defects and the specimen geometry should reflect the material properties. 27 The compressive strength properties of composites reported in the literature have large scatter.…”

Tension-Compression Fatigue Induced Stress Concentrations in Woven Composite Laminate

“…Investigating the fatigue behaviour under T-T loading is relatively simple due to the uncomplicated nature of the loading mechanism. However, the tension-compression (T-C) and compression-compression (C-C) fatigue loadings on large samples are complicated due to the involvement of anti-buckling rods that prevent buckling during loading [13]. Due to this complexity, the T-C and C-C fatigue studies are usually performed on specimens with very small gauge lengths (~15 mm) [14].…”