Mechanical characterization of anisotropy on a carbon fiber sheet molding compound composite under quasi-static and fatigue loading

Abstract

The paper presents an experimental analysis of the anisotropic effects of the structural advanced carbon fiber sheet molding compound composites (AC-SMCs) subjected to quasi-static and fatigue loading. Two configurations of AC-SMC composites (randomly oriented and highly oriented) considering three different orientations (0°, 45°, 90°) with respect to the material thermo-compression flow direction are investigated under quasi-static and fatigue tensile loading. The effects of fibers orientation induced by the thermo-compression process are analyzed in terms of ultimate strength, elastic modulus, and macroscopic damage corresponding to the stiffness reduction, and related to the quasi-static and fatigue behavior. For both loading conditions, the macroscopic damage of AC-SMC randomly oriented exhibits a two-stage evolution without any damage saturation prior to the samples' failure. In addition, the difference between the highly oriented and randomly oriented configurations is pronounced especially for the 45° and 90° orientations. Post-mortem X-ray radiography and SEM observations show that damage mechanisms such as microcracks appear between and inside bundles, and their occurrence depends on the sample orientation. Experimental findings are compared with those of an equivalent advanced glass fiber reinforced sheet molding compounds composite. The degree of anisotropy is more pronounced for AC-SMC. Indeed, the dependency of the behavior during the manufacturing process induces orientation. Furthermore, the damage evolutions of the two types of SMCs have displayed different kinetics, especially for the saturation stage which is not observed for the AC-SMC composite.

Carbon fibre sheet moulding compounds with high in-mould flow: Linking morphology to tensile and compressive properties

“…Nony-Davadie et al [28] have recently investigated the anisotropic response of CF-SMC induced by the high flow during compression moulding. They performed quasistatic tensile tests on CF-SMC specimens having an induced preferential orientation of 0°, 45° and 90°, and on specimens with no in-mould flow.…”

A thick-walled sheet moulding compound automotive component: Manufacturing and performance

“…A much smaller number of works investigates the link between manufacturing and mechanical properties [11,15,23]. However, those works were mainly focused on the induced tow orientation resulting from high in-mould flow, rather than on the effect of moulding parameters.…”

Effect of a Post-Fatigue Damage on the Residual Dynamic Behavior of Advanced-SMC Composites

“…In fact, one can note that basically, the automotive component is not always at an undamaged state. Indeed, in many applications, especially the automotive structural components, constitutive materials are subjected to vibration or oscillation forces [6][7][8][9] inducing a fatigue pre-damage accumulation prior to undergo the service loading. Thus, for a precise prediction of the dynamic response and the related energy absorption, the study of the material behavior exhibiting a fatigue pre-damage by performing fatigue tests prior high strain rate loading is of high importance.…”

“…An understanding of fatigue behavior is important for any material that experiences repeated loading during service [6][7][8][9]. Fatigue response of composites is usually characterized by an S-N curve, also known as a Wöhler curve [5,6].…”

“…It can be presented as a curve giving the value of cyclic stress amplitude, σ max, versus the number of cycles to failure, N. Fiber orientations, applied stresses, temperature, frequency, and self-heating effects are main parameters to reliably estimate the cyclic behavior of the materials [10][11][12]. Many authors [7] have indicated that augmentation of the fatigue stress, σ max , leads to a stiffness reduction rate and shorter fatigue life. The undamaged material constitution is defined in terms of the material elastic modulus, mass density, and yield stress.…”