Characterization and analysis of carbon fibre-reinforced polymer composite laminates with embedded circular vasculature

Abstract

A study of the influence of embedded circular hollow vascules on structural performance of a fibre-reinforced polymer (FRP) composite laminate is presented. Incorporating such vascules will lead to multi-functional composites by bestowing functions such as self-healing and active thermal management. However, the presence of off-axis vascules leads to localized disruption to the fibre architecture, i.e. resin-rich pockets, which are regarded as internal defects and may cause stress concentrations within the structure. Engineering approaches for creating these simple vascule geometries in conventional FRP laminates are proposed and demonstrated. This study includes development of a manufacturing method for forming vascules, microscopic characterization of their effect on the laminate, finite element (FE) analysis of crack initiation and failure under load, and validation of the FE results via mechanical testing observed using high-speed photography. The failure behaviour predicted by FE modelling is in good agreement with experimental results. The reduction in compressive strength owing to the embedding of circular vascules ranges from 13 to 70 per cent, which correlates with vascule dimension.

Interactions between propagating cracks and bioinspired self-healing vascules embedded in glass fibre reinforced composites

“…Two fabrication routes have been demonstrated, with the vascule preform material either laid between plies [15][16][17] or nested in precut recesses within the plies [18] during the stacking sequence. Regardless of the fabrication route utilised, it has been shown that the vascules should be aligned to both the local fibre direction and loading direction to avoid significant reductions in mechanical performance.…”

Design of an embedded sensor, for improved structural performance

“…The critical load case when embedding within composites is compressive, as a greater reliance is placed on the matrix and embedded item to carry load [11,12,13]. This is supported by the experimental work of Shivakumar and Emmanwori [12], which characterised the effects of embedding optical fibres within unidirectional carbon fibre laminates.…”

“…The simulated and experimentally observed load deflection gradients of the flexural specimens (groups D and E, Table 2) are shown in Table 7 interlaminar stresses [6,10,11,13]. The finite element results in this section ( Figures 8a and 8b), identify the interlaminar stress concentrations created by embedding the inductively coupled sensors within the flexural strength specimens, aiding with the interpretation of the results of the flexural strength testing (Table 5).…”

“…The inductively coupled sensors have a total diameter of 50 mm and maximum thickness of 0.45 mm. Whilst the sensors are large in comparison to other embedded inclusions such as self healing vascules and fibre optic sensors [11,12,13], they possess the advantage of being remote devices which use ultrasonic waves to interact with damage, this allows the sensors to be embedded in relatively unloaded through-thickness locations and structural positions. The aim of this study was to identify the optimum strategy for embedding thin remote sensing devices, with comparatively large in-plane dimensions inside composite materials.…”

Optimisation of an air film cooled CFRP panel with an embedded vascular network

“…During lay-up, 1.1 mm diameter Polytetraflouroethylene (PTFE) coated wire was lain along four paths that would form the cooling vessels. During curing, molten resin flows around the PTFE coated wire, and after curing, the wires were pulled out leaving a smooth circular unlined internal void [21]. Fittings were glued to the inlet points of each vessel to connect to an air supply.…”