On creep, recovery, and stress relaxation of carbon fiber‐reinforced epoxy filament wound composites

Abstract

This work encompasses an analytical procedure and experimental tests for the study of creep/recovery, stress relaxation, and viscoelastic behavior, focusing on the glassy state, of carbon fiber‐reinforced epoxy filament wound composites of distinct fiber orientation: [0]4, [30]4, and [60]4. The laminate with longitudinally aligned fibers did not show significant creep and its storage modulus was the highest in comparison to the other angles. Both creep and recovery responses were studied based on a Weibull distribution approach at two stress levels (2 and 5 MPa) and the results were found more comprehensive for the highest level. Stress relaxation modulus was calculated using 1% strain and decreased with the fiber orientation angle. The results were corroborated by those of isothermal tests based on non‐linear regression. POLYM. ENG. SCI., 58:1837–1842, 2018. © 2017 Society of Plastics Engineers

Effect of Nano-Reinforcement Topologies on the Viscoelastic Performance of Carbon Nanotube/Carbon Fiber Hybrid Composites

“…The load relaxation tests carry the advantage of revealing a multitude of strain rates compared to a single strain rate in a steady creep test [ 12 ]. The stress relaxation tests play a major role in revealing the composite materials’ viscoelastic/viscoplastic behaviors [ 40 , 41 , 42 , 43 , 44 , 45 ]. Stress relaxation tests provide the rate of decrease in stress for any state of stress that results from maintaining a constant strain during uniaxial loading.…”

Time-temperature behavior of carbon/epoxy laminates under creep loading

“…This parameter is temperature-dependent because the bulk material tends to become softer with temperature, which decreases the instantaneous modulus (Fancey 2005;Xu et al 2010;Yang et al 2006aYang et al , 2006b). This parameter can be associated with the storage modulus in the glassy region, where higher temperatures decrease the modulus when compared to the same static stress applied (Almeida et al 2018a(Almeida et al , 2018b. These results suggest that it is difficult to have some viscous flow on the bulk material due to a higher elastic deformation at a short-time response.…”

“…At 210°C the values are similar, given the fact that the chains are in high viscosity state (without energy storage). Considering that the stretched exponential is referred to the time relative to 63.2% of deformation, this deformation occurs in a narrower time for the same time interval when comparing the glassy and elastomeric regions (Fancey 2001(Fancey , 2005Almeida et al 2018aAlmeida et al , 2018b.…”

“…Significant progress has been carried out in terms of the time-independent behavior of CFRP composites. However, in engineering applications, compliance and deformation properties are stress-and time-dependent (Almeida et al 2018a(Almeida et al , 2018bOrnaghi et al 2020).…”

Creep/recovery and stress-relaxation tests applied in a standardized carbon fiber/epoxy composite: Design of experiment approach

“…Other mechanical properties studied are creep, 5,6 recovery, 7,8 and stress relaxation. 9,10 Creep is the permanent deformation in a material when subjected to a constant force or stress, being a function of time. Recovery is the recoverable strain resulted from stress removal.…”