Interlaminar Fracture of Random Short-Fiber SMC Composite

Abstract

The interlaminar fracture behavior of a random short-fiber SMC composite is studied both experimentally and analytically. In the experimental phase of the study, the random short-fiber SMC-R50 composite with different thicknesses is used. The commonly used double-cantilever-beam (DCB) fracture test is employed to evaluate the mode-I interlaminar fracture toughness. In the analytical portion of the research, owing to significant deformation in the DCB test, a geometrically nonlinear analysis is introduced to account for large deflection and nonlinear load-deflection curves in the evaluation of the interlaminar fracture toughness. For the SMC-R50 material studied, the interlaminar toughness of the composite is found to be an order of magnitude higher than that of unreinforced neat resin due to unusual damage mechanisms ahead of the crack tip and significant fiber bridging across crack surfaces. The effect of com posite thickness on the interlaminar fracture is appreciable. The influence of the SMC material microstructure on interlaminar crack resistance is discussed in detail.

Characterization of Damage and Fracture Processes in Short Fiber BMC Composites by Acoustic Emission

“…These differences all suggest that the fibers play an important role in both damage accumulation during deformation and crack propagation at fracture. Similar damage and fracture process have been observed by other investigators [3,5,7] in fatigue crack propagation experiments. In this case, the order of magnitude increase in fatigue toughness of an SMC over the resin was associated with formation of small cracks in a damage zone ahead of the crack tip while the propagating crack followed a tortuous pathway spanned by numerous pulled-out fibers.…”

“…The heterogeneous nature of sheet molding compound (SMC) and bulk molding compound (BMC) produces a structure with numerous stress concentrators. As a result, fatigue and fracture studies have shown the failure to be highly flaw sensitive [1,2,3] and subsequently the materials are more brittle than is desireable.…”

Compressive Stability of Delaminated Random Short-Fiber Composites, Part II—Experimental and Analytical Results

“…The letter R refers to randomly oriented, chopped fiber strands, and the number following indicates the weight percent of reinforcing fibers.) This particular short-fiber composite was used because its mechanical properties were readily available in the literature [2][3][4][5][6][7][8][9][10]. The reinforcement was OCF 433AB-114 roving glass filaments, chopped to a length of 25.4 mm (1.0 in.).…”

Identification of embedded interlaminar flaw using inverse analysis

“…Nakamura et al (1995) also showed that embedded delamination in composite could trigger a collapse at lower loads than the original critical buckling load. The delamination behaviors under dynamic loadings were studied by Grady and Sun (1986), Sun and Manoharan (1989) and Wang et al (1984). These investigations underlined the importance of identifying such a delamination to assess the residual strength of a composite panel and prevent possible catastrophic failures.…”