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Title: Mechanical performance and self-sensing for through-thickness reinforced composites
Author: Zhang, Bing
ISNI:       0000 0004 6059 0057
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2015
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This dissertation is focused on predicting the mechanical performance and damage self-sensing capability of composite laminates reinforced through the thickness with carbon Z-pins. A micro-mechanical finite element (FE) modelling strategy is developed for the analysis of the through-thickness reinforcement performance of Z-pins. This three-dimensional modelling approach is capable of describing the micro-structural features of Z-pinned laminates based on a versatile ply-level mesh. These features include the actual laminate stacking sequence, the presence of resin pockets surrounding the Z-pin, as well as the inherent misalignment of the through-thickness reinforcement. The Z-pin laminate interface is simulated by cohesive elements and frictional contact. The progressive failure of the Z-pin is modelled considering shear-driven internal splitting, accounted for using cohesive elements, and tensile fibre failure, modelled using the Weibull criterion. The modelling approach is verified via the experimental results of quasi-isotropic laminate coupons reinforced by single T300/BMI Z-pins. Carbon Z-pins enable a delamination self-sensing function in composite laminates. A sensing system able to detect the presence and size of interlaminar cracks in Z-pin reinforced laminates is here proposed and implemented. The system consists of a self-sensing structure, i.e. a Z-pinned laminate, and a sensor reading and analysis (SRA) system. The through-thickness electrical resistance (TTER) is considered as sensing variable. This requires bonding conductive epoxy electrodes to the laminate surfaces. Mode I and II tests are performed on single Z-pin reinforced laminates and double-cantilever laminated beams reinforced with Z-pin arrays. Results show that the TTER ·signal can be used to monitor delamination as well as the bridging state in individual Z-pins. A novel FE modelling strategy is proposed and verified to predict the toughness enhancement due to the insertion of delamination-sensing Z-pins.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available