Effects of hygrothermal aging on the thermomechanical properties of a carbon fiber reinforced epoxy sheet molding compound: An experimental research

Abstract

Carbon fiber sheet molding compounds (C-SMCs) are discontinuous fiber reinforced composite materials. Among them, epoxy-based C-SMCs are becoming relevant materials due to their high thermomechanical performance and better formability than continuous fiber reinforced composites. The thermomechanical performance of epoxy resins and epoxy based continuous carbon fiber composites have shown to be influenced by hygrothermal aging. In this work, this influence is studied for an epoxy-based C-SMC. Epoxy-based C-SMC samples were hygrothermally aged by means of accelerated conditioning, exposing them to 65% relative humidity, and 80 C in a climatic chamber. The equilibrium moisture content, as well as the moisture diffusion coefficient has been determined. The thermomechanical properties of epoxy C-SMC have been analyzed by dynamic mechanical analysis, tensile, 3-point bending, and short beam tests in dry and aged samples. The results showed that epoxy C-SMC is affected by hygrothermal aging in the cases of moisture intake and its effects on T g value, but interestingly, the hygrothermal aging did not generate any degradation effects in the mechanical response of epoxy C-SMC.

Improvement of structural vibration damping performance of SMCs through SMC/TPE sandwich structures

“…Being thermoset based composites, SMCs use to exhibit high stiffness values and high glass transition temperature ( T g ) values 9,10 . These two properties are usually associated to low vibration damping capabilities at room temperature, 11,12 which in fact, could be a detrimental factor against the demanding NVH behavior requirements of HEVs.…”

“…[5][6][7][8] Being thermoset based composites, SMCs use to exhibit high stiffness values and high glass transition temperature (T g ) values. 9,10 These two properties are usually associated to low vibration damping capabilities at room temperature, 11,12 which in fact, could be a detrimental factor against the demanding NVH behavior requirements of HEVs. Consequently, in order to fulfill the vibration damping requirements of the modern mobility industry, research studies need to be performed for improving the damping capabilities of SMCs.…”

SMC/TPE bi‐layer configurations for structural vibration damping applications

“…[4][5][6] SMC components are characterized by high glass transition (T g ) values and so a relatively poor vibration damping performance at around room temperature. [7][8][9] Then, when operating at this temperature, the vibration of SMC structures would lead to detrimental effects such as noise, dynamic stresses that shorten the structural fatigue life and reduced performance. [10][11][12] Therefore, enhancing the vibration damping capacity of SMC structures represents an interesting field to be studied.…”

An evaluation of the curing characteristics of thermosetting epoxy carbon fiber sheet molding compounds and validation through computer simulations and molding trials

“…Finally, for validation purposes, experimental compression molding trials have been completed in order to generate samples with different curing degrees at two different molding temperatures. The curing degree of the samples was determined by water intake process based on the hydrophilic nature of the present SMC material 42 stablishing a relationship between the water intake and crosslinking density of thermoset resins 43 . The obtained experimental results were compared with the cure predictions run by the software, operating as a function of two curing characterization techniques, in order to check the accuracy of the proposed methodology.…”