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Title: Modelling the behaviour of composite structures under impact and crush loading
Author: Tan, Wei
ISNI:       0000 0004 6060 0964
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2016
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Composite materials are finding increasing utilisation in a number of transportation industries concerned with making structures lighter to reduce environmental impact and improve efficiency. Nevertheless, composite structures are susceptible to damage from low-velocity impact events leading to a significant reduction in compression- after-impact residual strength. Another major challenge is to ensure a prescribed level of crashworthiness of fibre-reinforced composite vehicles. The accurate assessment of the effect of impact damage and the performance of structures under crush loading for composite aerostructures, for example, currently requires costly and highly inefficient experimental testing to meet certification requirements. The aim of this project is to develop and validate a reliable, predictive material damage model for capturing impact damage, residual strength and energy absorption capacity of thermoset and thermoplastic composites for crashworthiness assessments. A mesoscale intralaminar damage model, which combines a range of novel techniques to accurately capture the material response under damaging loads, was developed. This physically-based model makes a significant contribution to composite modelling capability by accounting for the intralaminar nonlinear material response, unloading/reloading and load reversal behaviour, fibre-dominated and matrix-dominated damage mode interactions and robust characteristic length calculation. A cohesive zone model, with mixed-mode softening law, was used to model the interlaminar damage. The presented model requires only physically measureable parameters, such as geometry, ply-level material properties and loading conditions, to achieve an accurate predictive solution of impact and crush behaviour of composite structures. A series of tests have been conducted for the measurement of interlaminar and intralaminar fracture toughness as well as the non-linear shear behaviour of AS4/PEKK thermoplastic composite laminates. The measured intrinsic ply-level values were then used as input material parameters for the finite element analysis. The effectiveness of the composite damage model was validated using experimental data obtained from in-house experimental testing as well as from the literature. Results showed that the model can accurately predict the intralaminar damage features, delamination damage area of composite structures under low-velocity impact as well as compressive behaviour and residual strength in compression after impact. Both the qualitative and quantitative aspects of intralaminar and interlaminar damage for wedge-shape and corrugated-shaped composite structures under crush loading were accurately captured. The predicted crush morphologies, force displacement response and dissipated energy were in a good agreement with experimental results, which demonstrates the reliability of this model in predicting impact and crush response of composite structures. The proposed model can be exploited by industry to reduce time and cost in the development of composite structures.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available