Interface strength of glass fibers in polypropylene: Dependence on the cooling rate and the degree of crystallinity

Abstract

The article experimentally investigates the interface strength of glass fibers in polypropylene (PP) with two different levels of crystallinity. The different degrees of crystallinity, 46.6% and 52.5%, were achieved using fast (quenching, ~4500°C/min) and slow (~2°C/min) cooling, respectively, during production of the PP film. The degree of crystallinity was measured using the differential scanning calorimetry. The mechanical properties of the films were characterized with the dynamic mechanical analysis and with a tensile test on Deben micro‐tester. Interfacial shear strength (IFSS) of glass fiber/PP was determined using fiber fragmentation test. Interfacial normal strength (IFNS) was determined using inverse identification based on finite‐element modeling of transverse tensile loading of a single fiber (Deben micro‐tester with digital image correlation‐based observation of the debonding). The measurements have confirmed the expected trend in mechanical properties of the film: increase of the storage and Young's moduli (room temperature) with the increase of degree of crystallinity, accompanied by the decrease in the loss modulus and tan δ. Interfacial strength followed the trend of the PP stiffness: both the IFSS and IFNS values for the PP with high crystallinity (slow cooling) are three (IFSS) and four (IFNS) times higher than those for the low crystallinity (fast cooling) case.

Splitting failure of a composite under longitudinal tension

“…Compared with the failure mode shown in Figure 2A, there is no smooth fracture surface plane. [35] Instead, scattered bundles of continuous fibers are a typical feature of this failure mode, which is apparently resulted from a matrix failure occurring earlier than fatal failure. [10,36,37] The measured longitudinal tensile load at this failure mode is moderate, in between the loads attained at the first and the second failure modes.…”

Interfacial adhesion quality in 3D printed continuous CF/PA6 composites at filament/matrix and interlaminar scales

“…Fragmentation tests have been widely used at the scale of single fibre [30][31][32][33][34][35], or at the scale of yarn [36,37]. For 3D printed composites, the interesting scale is the carbon filament one.…”

Impact Energy Dissipation and Quantitative Models of Injection Molded Short Fiber-Reinforced Thermoplastics

“…Among the factors originating from the fiber-matrix interface, interfacial shear strength (IFSS) and interfacial strength (IFS) have attracted attention as factors controlling the mechanical properties of fiber-reinforced plastics. In fact, pull-out [6], push-out [7], fragmentation [8,9], and pinhole pull-out methods [10] have been proposed to evaluate IFSS. The tensile test [11] has also been proposed to evaluate IFSS.…”