On the Influence of Fatigue Damage in Short-Fibre Reinforced Thermoplastic PBT GF30 on Its Residual Strength under High Strain Rates: An Approach towards Simulative Prediction

Abstract

Only by using accurate material data can precise simulation results be achieved. This principle also and especially applies in the field of crash simulation. However, in the simulation of short-fibre reinforced thermoplastics, material parameters are usually used that originate from the material testing of as-new samples. In order to get closer to the condition on the roads, where not only new vehicles are driving, the influence of service loads on the crashworthiness has to be investigated. This paper reports on studies of PBT GF30, a polybutylene terephthalate reinforced with 30% glass fibres, in which fatigue damage was induced in the material by cyclic loading. The residual strength was then determined in a high-speed experiment and compared with the strength of virgin samples. In order to enable the usability of the findings in the simulation, a modified failure criterion was implemented that takes the previous fatigue damage into account. The prediction quality of the simulation model was compared with the experimental findings and it can be concluded that there is good agreement.

Design and Additive Manufacturing of a Passive Ankle–Foot Orthosis Incorporating Material Characterization for Fiber-Reinforced PETG-CF15

“…Further research in the sectors of AM and topology optimization of orthoses was conducted, for example, by Leary et al [24], Lin et al [25], Lin et al [26], and van Lieshout et al [27]. In previous work, material testing and characterization were performed by Witzgall et al [28,29] to provide the basis for usable AM and topology-optimized FRP products. In addition, the study of Valvez et al [30] shows that when fibers were added to plastics, higher stress relaxations and compressive displacements were observed.…”

Using machine learning to increase efficiency in design of experiments for cyclic characterization of fibre-reinforced plastics

“…It has been shown that a temperature increase of more than 10°C can lead to a rapid decrease in strength and undesired thermal failure [14,15]. An excessive temperature rise can be caused by internal friction during testing.…”

Adjunctive Damage Model to Describe the Interaction of Different Defect Types in Textile Composites on the Strain-Rate-Dependent Material Behaviour

“…NCF-composites can be compromised by defects that arise during manufacture, like voids [3,4] and fibre misalignments [5][6][7]. However, defects can also occur during product use, such as fatigue [8][9][10] or impact [11][12][13]-induced cracks (further on referred to as service-related defects).…”

“…Investigations on the influence of voids on the strain-rate-dependent material behaviour of FRP have been presented by the author in [28]. The first approaches for modelling the strain-rate-dependent deformation behaviour have been published for glass-fibrereinforced thermoplastics [10,48,49] and thermosets [8,50,51]. Potentially existing defects due to previous damage caused by service loads are only considered in [10].…”

“…The first approaches for modelling the strain-rate-dependent deformation behaviour have been published for glass-fibrereinforced thermoplastics [10,48,49] and thermosets [8,50,51]. Potentially existing defects due to previous damage caused by service loads are only considered in [10]. In summary, the studies on the influence of defects on material behaviour always focus on one type of defect (voids or pre-fatigue).…”