Comparison of Quasi-static and Cyclic Fatigue Delamination Resistance of Carbon Fiber Reinforced Polymer-matrix Laminates under Different Mode Loading

Abstract

Delamination resistance data from different carbon-fiber reinforced polymer-matrix (CFRP) composites are compared for different loading modes, i.e., quasi-static and cyclic fatigue, opening tensile mode I, in-plane shear mode II, and fixed-ratio mixed-mode I/II. For this, data from round robin tests conducted at the authors laboratories will be complemented by selected results from literature. Questions related to delamination resistance of CFRP composites with implications for composite structural design and testing include, e.g., the determination of threshold values in cyclic fatigue, the question of conservative mode (mode I versus mode II), approaches for data analysis, and possible analogies in short crack cyclic fatigue between fracture behavior of structural metal alloys and CFRP. The scatter in Paris-type law data analysis of cyclic fatigue tests and the resulting apparent threshold behavior that has implications for composite structural design will be presented. Load measurement resolution yields the major contribution to scatter in displacement controlled fatigue tests. The analogous displacement resolution for load controlled tests is discussed and limitations in test control and of power law displacement data fitting for analysis are pointed out.