Fatigue performance of discontinuous fibre-reinforced thermoplastic leaf spring

Abstract

The present work investigates the fatigue performance of fibre-reinforced injectionmoulded leaf springs. Twenty per cent discontinuous long, short glass fibre-reinforced polypropylene (SFPP) and unreinforced polypropylene (UFPP) materials are used for manufacturing constant-thickness, varying-width, mono leaf spring. Fatigue tests are performed on moulded leaf springs at various alternating loads under the pulsating compression mode at 0.5 Hz frequency with the aid of in-house developed fixtures integrated with the servo-hydraulic fatigue machine. During fatigue testing, cyclic load-deflection of the test leaf spring of each and every cycle is measured; the energy dissipation ratio and spring rate of the test leaf springs are reported as an index for the accumulated damage at various stages of its life. Test leaf springs are subjected to fatigue load up to 2 × 10 5 cycles or failure, whichever is earlier. SFPP and UFPP leaf springs exhibited drops in the spring rate, whereas long glass fibre-reinforced polypropylene exhibited fracture as leaf spring failure. Fatigue performance as well as failure morphology of the leaf springs confirmed the role of reinforced fibre length in the thermoplastic composite leaf spring.

Long‐term failure of transversely loaded glass/iPP

“…For example, in the automotive industry, low weight requirements lead to smaller volumes, resulting in hotter engine compartments. Besides, there is a growing interest in the automotive industry to produce car cross beams and leaf springs made of thermoplastic composites, for which design temperatures up to 65 and 80°C, respectively, may be needed 18–21 …”

Fatigue Damage Assessment and Lifetime Prediction of Short Fiber Reinforced Polymer Composites—A Review

“…However, cyclic loading causes a continuous increase in the damage degree that is reflected in changes in the dynamic modulus (Figure 3). Subramanian and Senthilvelan have shown [74] that stiffness reduction during fatigue tests manifests itself differently for various materials, test schemes, and failure mechanisms. In some cases, no changes are observed at all.…”

A review of Long fibre thermoplastic (LFT) composites

“…As an important member of the composite family that offers both processability and superior properties, LFTs are expected to see continuously increasing use in automobiles and the automotive industry will remain the prime consumer of LFTs over the next 20 years. LFTs have been used mainly secondary structural automotive components such as front end modules [17,102,104–110], underbody panels [105,107,110,111], trunk lids [105], hatchbacks [102,107], seat components [17,102,105,107,110,112,113], door components [17,102,105,107,110,114,115], instrument panel carriers [17,102,104,105,107], spare-wheel pans [102,105,107], bumper beams [102,105,107,110,116,117], roof modules [107], leaf springs [118,119], brake pads [120], engine hoods [121], battery trays [121], wheels [122], and sound absorbing shells [105,107]. Figure 3 shows some of the typical automotive components made using LFTs [102…”