The influence of physical ageing on the in-plane shear creep compliance of 5HS C/PPS
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The influence of physical ageing on the in-plane shear creep compliance of 5HS C/PPS E.R. Pierik1 · W.J.B. Grouve1 · M. van Drongelen1 R. Akkerman1
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Received: 5 December 2018 / Accepted: 12 April 2019 © The Author(s) 2019
Abstract Thermoplastic polymer-matrix composites, such as carbon woven fabric reinforced poly(phenylene sulphide) (C/PPS), are increasingly used in the aircraft industry. Primary structural applications, however, are limited due to uncertainty concerning the longterm behaviour. Recent work indicated a progressive creep response over time, which would render these materials unusable for such applications. However, the effect of physical ageing was neglected, which is well known to alleviate the creep behaviour and hence physical ageing is rigorously included in this study on the long-term creep response of C/PPS. Shortterm tensile creep tests in the bias direction were performed at temperatures of 50, 60, 65, 70, 75 and 80◦ C to obtain a master curve using the time–temperature superposition principle. Ordinary horizontal shifting failed to produce a smooth curve and therefore three alternative approaches were used and compared. The physical ageing rate was, however, characterised with horizontal shifting only at 50◦ C and was implemented by means of the effective time theory (Struik, 1977) to correct the momentary master curves for the influence of physical ageing. The resulting predictions are more realistic and demonstrate that the structural changes in a material reduce the creep rate over time. Hence, the long-term creep compliance tends to increase asymptotically towards a finite value, in contrast to the unbounded momentary response. Keywords Polymer-matrix composites (PMCs) · Thermoplastic resin · Creep · Physical ageing · 5HS C/PPS
1 Introduction For some decades, composite materials in the form of fibre-reinforced polymer-matrix composites (PMCs) have been used to replace metal alloys in structural applications (Hastie 1991). The main reasons are the higher strength-to-weight and strength-to-stiffness ratios
B M. van Drongelen
[email protected]
1
Faculty of Engineering Technology, Chair of Production Technology, University of Twente, Drienerlolaan 5, 7255 NB Enschede, The Netherlands
Mech Time-Depend Mater Fig. 1 Long-term in-plane shear creep experiment according to the ASTM D3518/D3518M standard (with a shorter specimen length of 180 mm) on C/PPS material at 50◦ C and τ12 = 5 MPa with Kohlrausch–Williams–Watts (KWW) model fit as outlined by Motta Dias et al. (2016)
compared to metal alloys, which results in a weight reduction. The ongoing development is most evidently seen in the aircraft industry, where the use of composites has grown steadily over the past decades up to a point where PMCs now make up 53% of the Airbus A350’s structural weight (Airbus 2018). Civil aircraft are common to remain in service for 25 years, some even operate for nearly 50 years (Smith 2017). Clearly, the aircraft should be designed with this in mind, which requires insight in the long-term
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