3D printing-assisted interphase engineering of polymer composites: Concept and feasibility

We introduced a general concept to create smart, (multi)functional interphases in polymer composites with layered reinforcements, making use of 3D printing. The concept can be adapted for both thermoplastic and thermoset matrix-based composites with either thermoplastic- or thermoset-enriched interphases. We showed feasibility using an example of a composite containing a thermoset matrix/thermoplastic interphase. Carbon fiber unidirectional reinforcing layers were patterned with poly(ε-caprolactone) (PCL) through 3D printing, then infiltrated with an amine-cured epoxy (EP). The corresponding composites were subjected to static and dynamic flexure tests. The PCL-rich interphase markedly improved the ductility in static tests without deteriorating the flexural properties. Its effect was marginal in Charpy impact tests, which can be explained with effects of specimen and PCL pattern sizes. The PCL-rich interphase ensured self-healing when triggered by heat treatment above the melting temperature of PCL

Analysis Of Low Temperature Impact Fracture Data Of Thermoplastic Polymers

Impact fracture toughness of polypropylene (PP) blends, high density polyethylene (HDPE) and rubber toughened polymethylmethacrylate (RTPMMA) has been studied by means of three-point bending falling weight impact testing at different temperatures ranging from -60 degrees C to room temperature using the cleavage fracture toughness, JC parameter [ASTM E1820-99a]. The latter Fracture Mechanics methodology was chosen due to its simplicity [Fasce et al., 2003]. Traces of the impact tests were analyzed using an inverse methodology just proposed by Pettarin et al. (2003). This methodology makes it possible to obtain from a three-point bending instrumented impact test the mechanical response of the material, discarding the dynamic effects associated with the test. The results show that the average JC values calculated with treated and untreated data are similar for a given material, while the standard deviations are larger when the calculations are made with the untreated data. It is clear that the inverse methodology used to correct the data reduces error propagation, giving place to more precise estimations, and therefore more reliable JC values

Investigation of fiber/matrix adhesion: test speed and specimen shape effects in the cylinder test

The cylinder test, developed from the microdroplet test, was adapted to assess the interfacial adhesion strength between fiber and matrix. The sensitivity of cylinder test to pull-out speed and specimen geometry was measured. It was established that the effect of test speed can be described as a superposition of two opposite, simultaneous effects which have been modeled mathematically by fitting two parameter Weibull curves on the measured datas. Effects of the cylinder size and its geometrical relation on the measured strength values have been analyzed by finite element method. It was concluded that the geometry has a direct influence on the stress formation. Based on the results achieved, recommendations were given on how to perform the novel single fiber cylinder test

Creep behaviour of injection-moulded basalt fibre reinforced poly(lactic acid) composites

In this paper, the creep of short (chopped) basalt fibre reinforced poly(lactic acid) composites was investigated; 5, 10, 20 and 30 wt.% short basalt fibre reinforced composites were prepared by using twin-screw extrusion followed by injection moulding. Differential scanning calorimetry measurements revealed that the basalt fibres had nucleating effect on the poly(lactic acid)grade used in this study, while scanning electron microscopy demonstrated that there was strong adhesion between the fibre and the matrix. Fibre distribution analysis showed that there was no significant statistical difference between the average fibre lengths of all of the produced composites. Finally, creep mastercurves were constructed using the single creep curves obtained by applying 10, 20, 30,…, 90% of the tensile strength of the composites as a static creep loading force. It was demonstrated that the basalt fibres as reinforcements can effectively reduce the strain and increase time to failure of the composites during creep load and thus could open the possibilities for poly(lactic acid)-based composites to be used in long-term constantly loaded structural or engineering applications. </jats:p