In the continuing effort to understand the processes involved during the compressive failure of statically and dynamically loaded composite structures, this work is concerned with the role the fiber, matrix, and interphase play in determining a composite's compressive performance. Fourteen material systems representing permutations of four carbon fiber systems, three matrix systems, percentages of fiber surface treatment, and three sizing conditions have been laminated and cut into coupons. The bond strength arising from the particular combination of fiber, surface treatment, sizing, and matrix is quantified by measuring the transverse flexural strength of each material system.
Center-holed, cross-plied specimens of each of the 14 materials were tested in quasi-static compression to determine their structural strength. An attempt was then made to correlate differences in compressive strength to differences in the properties of the three phases. A fixed percentage of each strength value was then utilized to establish the tension-compression fatigue stress level employed for each of the 14 material systems. Damage analysis revealed the mechanisms responsible for the wide variation in fatigue life witnessed. The interphase is seen to play a second-order role in determining the compressive strength of these particular notched cross-plied laminates. On the other hand, the interphase is shown to be a key variable in dictating these laminates' compression-dominated fatigue behavior.