Daniel Thomson

Dynamic crushing of composites is studied proposing an optimised experimental design: flat, millimetre-scale specimens reduce geometrical influences and facilitate detailed numerical studies. Crushing behaviour is investigated on a universal testing machine and a drop-tower at varying loading rates using two different force measurement techniques....

Electrospinning technique is well-known for the generation of different fibers. While it is a "simple" technique, it lies in the fact that the fibers are typically produced in the form of densely packed two-dimensional (2D) mats with limited thickness, shape, and porosity. The highly demanded three-dimensional (3D) fiber assemblies have been explor...

The determination of the mechanical response of engineering materials subjected to high loading rates plays an important role in determining their performance and application. The high strain rate tensile response of metals is usually investigated by means of the Split Hokinson Tension Bar (SHTB) apparatus. The interpretation of the obtained result...

The dynamic failure of short carbon fiber reinforced polyether-ether-ketone (SCFR-PEEK) composites under biaxial stresses was investigated in this paper. Cruciform specimens were loaded with a biaxial split Hopkinson tensile bar system, and a high-speed camera was utilized to record the deformation and failure processes. A nonlinear numerical model...

The mechanical behaviour of unidirectional fibre-reinforced composites is typically assumed to be linear elastic before failure. However, these materials exhibit nonlinear responses while being loaded in the matrix and fibre dominated directions that are generally disregarded. This research explores alternative physically-inspired finite element ba...

Angle-ply carbon fibre reinforced polymer (CFRP) crush tubes were tested in drop weight impact experiments. High-fidelity computational modelling of the dynamic impact response was performed using explicit finite element analysis in LS-DYNA. Ply-by-ply and fibre-aligned meshing was used for the composite lamina wherein the intralaminar damage was t...

Strain-rate effects tend to influence the properties of composite structures subjected to highly dynamic loads. To further improve numerical evaluations of high-speed damage in carbon fibre reinforced polymers, drop weight impact experiments were conducted on coupon samples with triangular through-thickness triggers [1]. This simple geometry was se...

The capability to accurately analyze the response of multi-directional composite laminates during impact events is of high importance for the design of lightweight aircraft structures. In this work, both experimental and numerical analyses are performed covering a large design-space of laminates for all aspects from on-set of damage and barely visi...

The biaxial tensile failure of short carbon fibre reinforced polyether-ether-ketone (SCFR-PEEK) composites is characterized in this paper. An improved cruciform specimen was proposed to apply biaxial stresses, and five different stress ratios were employed in experiments. The stress distribution within the gauge section is not measurable across the...

The determination of the dynamic response of titanium alloys is vital for aerospace industrial applications. The present research investigates the effect of strain history and temperature on the dynamic strain localization in Ti-6Al-4V grade-5 alloy. The experimental campaign was conducted using a Split Hopkinson Tensile Bar (SHTB) equipped with an...

Drop weight impact experiments were conducted on angle-ply carbon fibre reinforced polymer (CFRP) composite crush tubes. The dynamic response was modelled using explicit finite element methods and continuum damage mechanics and cohesive zone modelling in both Abaqus/Explicit and LS-DYNA. User-defined constitutive models for the intra-ply behaviour...

Experimental results from 3D printed TPC (thermoplastic copolyester) compression specimens were used to develop a combined experimental-numerical framework to support the design of e.g. 3D printed mouthguards. First, a commercially available material model capable of representing the strain-rate dependent behaviour of materials undergoing large def...

A multi-scale modelling strategy is proposed to investigate the potential effects of hygrothermal ageing on the ballistic performance of CFRP laminates. At the micro-scale, damage evolution due to cyclic hygrothermal loads is simulated on a representative microstructure using an adapted fatigue damage law. Then, the results of the micro-mechanical...

The rate-dependent failure response of multi-material adhesive joints for three deformation modes is investigated. A combination of carbon fibre reinforced polymers (CFRP) and titanium alloy Ti-6Al-4V is employed. The experiments provide important information about the failure sequence of a multi-material adhesive joints, which depends upon the loa...

A series of dynamic longitudinal compression tests have been performed on cross-ply IM7/8552 specimens cut at different off-axis angles to produce different combinations of compression and shear stresses. Together with results from previous quasi-static tests of the same kind, quasi-static and dynamic fibre kinking failure envelopes have been obtai...

Longitudinal compression testing of unidirectional FRP laminates remains a challenge due to the difficulty in applying high compressive loads without stress concentrations and boundary effects leading to premature failure. This work aims to critically evaluate different specimen designs and laminate configurations, cross-ply in particular, for the...

Plate impact tests on IM7/8552 composite laminates with different projectile incident angles and velocities were carried out. Numerical simulations were conducted to predict the impact damage, with both Puck and LaRC failure criteria having been employed in this study. The dynamic failure performance of IM7/8552 lamina was reviewed first, by referr...

Three different approaches to plasticity are investigated to model the experimentally-observed non-linear behaviour of unidirectional fibre-reinforced polymeric matrix materials. The first and simplest approach consists on assuming independent one-dimensional rate-dependent plasticity on in-plane (12) and through-thickness longitudinal (13) shear c...

A new constitutive model is presented that aims to accurately tackle the effects of multiaxial loading, strain rate and hydrostatic pressure on unidirectional FRPs, while doing so in an intuitive and physically-based manner. In this model, it is assumed that yielding occurs primarily due to shear stresses acting on a critical localisation plane whi...

A new implementation of Puck's 3D Inter-Fibre Fracture criterion for unidirectional reinforced FRP laminates has been developed that improves the criterion in two main areas. First, a new treatment of strain rate effects on the inter-fibre fracture plane orientation has been included to improve the predictive capability of Puck's criterion outside...

This work focuses on the effect of strain rate and fibre rotation on the in-plane shear properties of composite laminates. The effect of fibre rotation on the measured shear properties, was for the first time experimentally quantified with the comparison between compression and tension tests of the ±45° laminate samples. Significant increase of she...