Viscoelastic and viscoplastic behavior of a fully recycled carbon fiber-reinforced maleic anhydride grafted polypropylene modified polypropylene composite

Abstract

The effect of maleic anhydride grafted polypropylene (MAPP) coupling agents on properties of a new composite made of recycled carbon fibers and recycled polypropylene (rCF/[rPP + MAPP]) was studied experimentally. This new material presented significantly improved properties, compared to the previous generation, without the addition of MAPP (Giannadakis K, Szpieg M and Varna J. Mechanical performance of recycled carbon fibre/PP. Exp Mech 2010; published online.). This was mostly attributed to improvement of the fiber/matrix interface. The inelastic and time-dependent behavior of the MAPP modified composite material in tension was analyzed. A series of quasi-static tensile and creep tests were performed to identify the material model, which accounts for: (a) damage-related stiffness reduction, (b)development of stress and time-dependent irreversible strains described as viscoplasticity, (c) nonlinear viscoelastic behavior. The damage-related stiffness reduction was found to be less than 10%. Although damage-dependent stiffness was not the main source of nonlinearity, it was included in the inelastic material model. In creep tests, it was found that the time and stress dependence of viscoplastic strains follows a power law, which makes the determination of the parameters in the viscoplasticity model relatively simple. The viscoelastic response of the composite was found to be linear in the investigated stress domain. The material model was validated in constant stress rate tensile tests.

Mechanical interfacial adhesion of carbon fibers-reinforced polarized-polypropylene matrix composites: effects of silane coupling agents

“…This shows that the oxygen functional groups and surface free energy values can determine the resulting adhesion strengths of the carbon fiber/polarized polypropylene matrix in this system. Practically, the well-known ring-opening crosslinking reaction between amino-silane coupling agents (APS) and polypropylene-co-maleic anhydride can dramatically enhance the mechanical interfacial strength [29][30][31][32][33][34] of a composite. However, we used partially polarized polypropylene (Ma 0.2 -PP 99.8 ) as a matrix.…”

Mechanical performance and modelling of a fully recycled modified CF/PP composite

“…The mechanical and thermal properties of the reprocessed PURE Õ scrap were earlier characterized by Szpieg et al 17,18 The polypropylene scrap material was compounded with MAPP coupling agents in order to improve the interfacial adhesion with the recycled carbon fibers. 9,10,12,18 Composite manufacturing…”

“…A series of creep tests were performed to obtain the parameters in the inelastic material model, which accounts for development of time-dependent irreversible strains described as viscoplasticity and nonlinear viscoelastic behavior. 9 For the viscoelastic characterization, single creep tests with a duration of 40 min and a recovery of eight times the loading period were performed. In addition, a test program to identify the time dependence and stress dependence of VP-strains in creep tests (constants: C VP , M, and m) described in references 9, 10, and 18 was employed.…”

“…Simulation was performed using a numerical integration to obtain viscoplastic and viscoelastic strains as described further in the section on material modelling. 9,10,18 Microscopy Fiber length measurement. One rCF/rPP composite sample with dimensions of 68 Â 46 Â 1.2 mm was placed in an oven (Nabertherm Controller B170) for 3 h at 450 C to burn-off the polymer matrix in order to separate the fibers from each other.…”

“…The results are presented in Figure 5. Here, ln(-ln(1-P f (r f )) is a representation of failure probability, see Equation (9) and reference 26. The Weibull shape parameter, ¼ 5.68, is obtained from the slope of the data presented in Figure 5 for ln(-ln(1-P f (r f )) vs. ln (r f ).…”