Philip Harrison

University of Glasgow | UofG · School of Engineering

Traditional inspection methods often fall short in detecting defects or damage in fibre-reinforced polymer (FRP) composite structures, which can compromise their performance and safety over time. A prime example is barely visible impact damage (BVID) caused by out-of-plane loadings such as indentation and low-velocity impact that can considerably r...

The present paper reports an overview of mechanochromic self-reporting thin-ply hybrid composite sensors, which are designed to visually indicate overload in structures. These sensors, made from combinations of high-strain and low-strain materials, change appearance earlier than the final fracture, providing a clear visual cue of damage like delami...

This paper studies the mechanochromic response of carbon/flax sandwich composites equipped with hybrid thin-ply glass/carbon composite sensors when exposed to the low velocity impact load. Also, the pre-cut carbon sensing layer is investigated as a potential strategy for improving the self-reporting function. The effectiveness of the mechanochromic...

Visual inspection is one of the most common non-destructive testing (NDT) methods that offers a fast evaluation of surface damage in aerospace composite structures. However, it is highly dependent on human-related factors and may not detect barely visible impact damage (BVID). In this research, low velocity impact tests with different energy levels...

Low-velocity impact (LVI) can happen during the manufacturing and in-service life of a composite structure, causing serious internal damages without a noticeable sign on the structure’s surface, often referred to as barely visible impact damage (BVID). This can lead to a catastrophic or unexpected failure, hindering the safer and wider application...

Recently, a novel thermoforming process involving induction heating of tin interlayers to create ‘lubricated blanks’ using low viscosity molten tin was demonstrated (“iMelt”) (Harrison et al., 2020). Important to the success of the method is expulsion of the tin interlayer from the blank using a multi-step thermoforming operation. Approaches to cha...

Recently emerging mechanochromic systems are becoming highly attractive for structural health monitoring (SHM) purposes in various industries, such as civil, wind, and aerospace, to improve the safety and performance of structures. These are based on self-reporting polymer composites which provide a lightweight sensor with an easy-to-read visual cu...

This paper aims to study the feasibility of smart thin-ply hybrid glass/carbon sensors in quasi-static impact damage detection and analyse different design strategies to achieve an optimal sensor performance. A set of carbon fibre reinforced polymer (CFRP) specimens was manufactured, and the hybrid sensing layers were attached and evaluated. New ar...

This paper reports on an investigation into stitching techniques used to secure woven tapestry artefacts to fabric supports. A research project used digital image correlation (DIC) as a method of evaluating commonly used tapestry support techniques, with stitching tests carried out on wool rep fabric and a historic tapestry fragment. Though it was...

This paper develops a finite element (FE) model of the single fibre fragmentation test designed for direct comparison with experimental results on an E-glass/epoxy system by McCarthy et al. (2015). Interface behaviour is modelled via a cohesive surface, and stochastic Weibull fibre strengths (determined by independent experiments) assigned at rando...

Composite materials and structures have witnessed substantial developments over the last few decades. Mechanochromic polymers are a new class of smart composites with the ability to self-report their health condition on-line. The design mechanism in these materials is such that initiation of any force or mechanical stimuli leads to a color change i...

Finite element generated synthetic image deformation is used to assess factors affecting the reliability and accuracy of strain fields measured by the DIC technique, when using the inherent historical tapestry image to track deformations. Compared with direct correlation with the reference image, incremental correlation is found to introduce accumu...

A novel low-cost manufacturing process is introduced, referred to as ‘Fabric Steering’. By manipulating biaxial fabrics, curvilinear fibre paths can be created to manufacture variable stiffness panels, similar to those produced using Automated Fibre Placement [1]. With low equipment costs and the capability to steer multiple-layers of fabrics simul...

Deep-draw experiments are performed on both glass and carbon fabric both to better understand the origin of wrinkle growth during complex forming experiments and to assess the accuracy, robustness and computational cost of forming simulations of engineering fabrics. During experiments, the shape of the deformed blanks is digitised using two differe...

A Matlab®-based numerical tool, ‘SteerFab’, is developed to predict steered fibre patterns and to analyse the mechanical properties of the resulting variable stiffness panels using the finite element software, AbaqusTM. Based on trellis shear kinematics [1], both the steered fibre pattern and the shape of the corresponding initial undeformed sheet...

Tapestries represent a key but fragile component of many historic collections, as well as a complex challenge for textile conservators who aim to ensure their preservation. Indeed, the heterogeneity of materials, weaving features and conservation history make it difficult to predict the mechanical and physical behaviour of these objects, especially...

This paper reports on an investigation into slanted support, an increasingly common method of displaying tapestries in mainland Europe. Two factors contribute to the efficacy of slanted supports for tapestry: the angle of display and the degree of friction between the tapestry and the support. Initial analysis demonstrated that a small degree of sl...

In recent years, Automated Fibre Placement has been applied in manufacturing variable stiffness panels containing continuously changing fibre paths. The aim is to achieve superior mechanical properties, compared to straight-fibre laminates [1,2]. This paper proposes a novel low-cost manufacturing technique, referred to here as ‘manual 2D fabric ste...

In the last decade, the exotic properties of pantographic metamaterials have been investigated and different mathematical models (both discrete or continuous) have been introduced. In a previous publication, a large part of the already existing literature about pantographic metamaterials has been presented. In this paper, we give some details about...

An analysis technique to assess the viability of digital image correlation (DIC) in tracking the full‐field strains across the surface of hanging historic tapestries is presented. Measurement uncertainty related to the use of the inherent tapestry image in tracking displacements is investigated through use of “synthetic” deformation fields. The lat...

We consider two `comprehensive' modelling approaches for engineering fabrics. We distinguish the two approaches using the terms `semi-discrete' and `continuum', reflecting their natures. We demonstrate a fitting procedure, used to identify the constitutive parameters of the continuum model from predictions of the semi-discrete model, the parameters...

The hot-forming process for thermoplastic composites is a very promising fabrication route for high volume applications. Reliable and fast numerical tools are needed to optimise the forming process and to support industrial exploitation. This paper presents the experimental validation of a finite element-based optimisation routine, which is used to...

In response to a previous investigation on the influence of specimen pre-shear and wrinkling on the accuracy of uniaxial bias extension test results (Alsayednoor et al. [1]), numerical and experimental investigations have been conducted, aimed at evaluating the use of transparent anti-wrinkle plates to mitigate errors due to wrinkling of engineerin...

The influence of unintended specimen pre-shear and out-of-plane wrinkling on the accuracy of shear angle and axial force results, measured during a uniaxial bias extension (UBE) test on engineering fabrics, is examined. Three techniques of measuring test kinematics are investigated, including manual image analysis, 2-D and 3-D full-field analysis....

Through a combination of direct measurement and inverse modelling, a route to characterising the main mechanical forming properties of engineering fabric is demonstrated. The process involves just two experimental tests, a cantilever bending test and a modified version of the uniaxial bias extension test. The mechanical forming properties of a twil...

This investigation evaluates various numerical algorithms; each designed to generate periodic 2-D Representative Volume Elements (RVEs) containing foam-like microstructures suitable for direct import into commercial finite element software for mechanical evaluation. The operation of each algorithm is discussed and the resulting RVEs are examined fr...

Shear-thickening fluid-impregnated aramid (STF-im-AR) fabrics have been manufactured for advanced soft body armor applications for which they provide improved ballistic and stab resistances. It is not yet clear whether or not such improvements can be attributed solely to the STF. In this study, the rate-dependent behavior of an STF-im-AR fabric was...

A major challenge in studying impact problems analytically is solving the governing equations of impact events, which are mostly in the form of nonlinear ODEs. This paper focuses on the solution of nonlinear models for impact problems in asymptotic cases, where local indentation is significant. The asymptotic cases consist of both half-space and in...

This short communication is intended to correct certain erroneous conclusions drawn in the recently published paper by Härtel and Harrison (2014). The investigation of Härtel and Harrison (2014) was intended to evaluate the performance of normalisation methods for the uniaxial bias extension test. Predictions of two published theories for rate-inde...

A bespoke test rig has been designed to facilitate testing of magneto-rheological (MR) elastomers (MREs) under equi-biaxial tension using a standard universal test machine. Tests were performed up to 10% strain on both isotropic and anisotropic MREs with and without the application of an external magnetic field. Assumptions regarding the material’s...

The isotropic and anisotropic magnetic permeability of Magneto-Rheological Elastomers (MREs) are identified using a novel, simple and low-cost approach. This involves measuring the magnetic flux density and attractive force occurring between magnets, when MRE specimens are placed in between the magnets. Tests were conducted using isotropic MREs wit...

A method of combining 1-d and 2-d structural finite elements to capture the fundamental mechanical properties of engineering fabrics subject to finite strains is introduced. A mutually constrained pantographic beam & membrane mesh is presented and simple homogenisation theory is developed to relate the macro-scale properties of the mesh to the prop...

Using a two-phase (rubbery and glassy) phenomenological model and shape memory strains, a three-dimensional constitutive model for shape memory polymers (SMPs) was developed that can simulate multi-axial and large deformation behavior (up to 200% of strain) of SMPs. To derive a constitutive equation, the total deformation gradient was multiplicativ...

The large deformation mechanics of biaxial engineering fabrics are of considerable interest due to the importance of sheet forming processes for the manufacture of advanced composite products and structures. The success or failure in forming a given geometry and the properties of the final composite component are in large part determined by the mat...

The elastoplastic impact response of a trimorph plate subjected to low-velocity large mass impact has been investigated using analytical models. In formulating the impact model, the displacement of the impactor, vibration of the plate and local contact mechanics were accounted for. The vibration of the trimorph plate was modelled using the classica...

The large-strain behaviour of Magneto-Rheological Elastomers (MREs) is characterised experimentally under uniaxial compression, uniaxial tension and pure shear deformation, in the absence and in the presence of magnetic fields. MREs are ‘smart’ materials that can alter their properties instantaneously by the application of external stimuli. They ho...

The impact response of an elastoplastic half-space is investigated using a recently-developed contact model that accounts for post-yield effects in the loading and restitution phases. First, a static analysis is performed to show the validity of the contact model. The impact histories for the indentation depth, velocity of the impactor, and the con...

The governing equation of a half-space impact is generally nonlinear and it is normally solved using numerical techniques that are mostly conditionally stable and require many iteration steps for convergence of the solution. In this paper, we present the force-indentation linearisation method (FILM), an approximate technique that produces closed-fo...

This paper describes a new force-based hinge element implemented in the framework of the Large Increment Method (LIM). The element can be of arbitrary cross section and is capable of including inelastic behaviour close to structural hinges. The element formulation can accommodate elasto-plastic strain hardening material behaviour. The solution proc...

Shear thickening fluid (STF) is a non-Newtonian fluid featuring the increased viscosity upon high strain rate applied. Recently, STF-treated aramid fabrics have been researched to enhance the bulletproof efficiency maintaining the lightweight, however their shear properties including tow shearing, which significantly contribute to the bulletproof p...

In this paper, the mechanical response of incompressible particle-reinforced neo-Hookean composites (IPRNC) under general finite deformations is investigated numerically. Three-dimensional Representative Volume Element (RVE) models containing 27 non-overlapping identical randomly distributed spheres are created to represent neo-Hookean composites c...

A numerical investigation has been conducted to determine the influence of Representative Volume Element (RVE) size and degree of irregularity of polymer foam microstructure on its compressive mechanical properties, including stiffness, plateau stress and onset strain of densification. Periodic two-dimensional RVEs have been generated using a Voron...

A pre-consolidated thermoplastic advanced composite cross-ply sheet comprised of two uniaxial plies orientated at 0/90° has been thermoformed using tooling based on the double-dome bench-mark geometry. Mitigation of wrinkling was achieved using springs to apply tension to the forming sheet rather than using a friction-based blank-holder. The shear...

In this paper, a non-orthogonal constitutive model [1] is used to investigate the effect of sample misalignment due to ‘tow meander’, across the initial blank sheet on the shear compliance of a woven glass fabric, as measured using the biaxial bias extension test with various transverse loads applied [2]. The same statistical distribution and spati...

This paper describes a new force-based hinge element implemented in the framework of the Large Increment Method (LIM). The element can be of arbitrary cross section and is capable of including inelastic behaviour close to structural hinges. The element formulation can accommodate elasto-plastic strain hardening material behaviour. The solution proc...

An approach to incorporate the coupling between the shear compliance and in-plane tension of woven engineering fabrics, in finite-element-based numerical simulations, is described. The method involves the use of multiple input curves that are selectively fed into a hypoelastic constitutive model that has been developed previously for engineering fa...

A theoretical background is proposed for the normalisation of biaxial bias extension results for rate-independent fabrics, whose shear compliance depends on both the shear angle and the fibre tension within the fabric. The theory is used to predict the form of biaxial bias extension results from known shear force–shear angle–fibre tension behaviour...

This article describes uniaxial compression tests on a melt-extruded closed-cell low-density polyethylene foam. The stress–strain response shows that the mechanical behaviour of the foam is predominantly transversely isotropic viscoelastic and compressible. Image analysis is used to estimate the Poisson’s ratio under large strains. When the deforma...

Modelling the forming process for engineering fabrics and textile composites using a mechanical approach, such as the finite element method, requires characterisation of the material’s behaviour under large shear deformation. For woven engineering fabrics, a coupling between in-plane tension and both shear compliance and the onset of wrinkling is t...

Variability of tow orientation is unavoidable for biaxial engineering fabrics and their composites. Since the mechanical behaviour of these materials is strongly dependent on the fibre direction, variability should be considered and modelled as exactly as possible for more realistic estimation of their forming and infusion behaviour and their final...

A commercial Finite Element (FE) code is used to simulate the forming of a thermoplastic viscous textile composite sheet. The main success of this work is in combining two distinct models. The first is a rate and temperature dependent unit cell energy model, designed to predict the shear force - shear angle - shear rate response of viscous textile...

A predictive approach to modelling the forming of viscous textile composites has been implemented in two finite element codes; Abaqus Standard™ and Abaqus Explicit™. A multi-scale energy model is used to predict the shear force–shear angle–shear rate behaviour of viscous textile composites, at specified temperatures, using parameters supplied readi...

Modelling the forming process of engineering fabrics and textile composites using a mechanical approach, such as FEM, requires characterisation of material behaviour. Using Picture Frame (PF) tests, several previous studies have reported a coupling between in‐plane tension and fabric shear compliance. However, characterising this behaviour accurate...

This chapter is focused on modelling the forming behaviour of biaxial non-crimp fabrics (NCFs). In Section 7.1, the motivation for modelling NCFs is given. Following a short description of the meso-structure of NCFs (Section 7.2) the effect of the stitch architecture on the shear and forming behaviour of NCFs is demonstrated. In Section 7.3, the tw...

Silicon carbide has been synthesised from silicon or silica combined with activated carbon or graphitevia microwave heating over timescales from minutes to seconds without the need for inert atmospheres or subsequent purification. The carbide morphology and phase purity can be controlled by the microwave cavity used and the power applied and hence...

Based on fiber reinforced continuum mechanics theory, a simple hyperelastic constitutive model is developed to characterize the anisotropic nonlinear material behaviour of woven composite fabrics under large deformation during forming. The strain energy function for the hyperelastic model is additively decomposed into two parts nominally representi...

Structural woven composites made with high strength fibres are now widely used in automotive and aeronautic engineering due to their high strength/weight ratio as compared with metals. During the forming process, though the extension of the woven composite fabrics is usually small, the shear deformation (i.e., the angle change between weft and warp...

Press forming of thermoplastic textile composites is a fast and efficient method of production. Friction occurring between the composite material and pressure blank-holder during forming imparts tensile stresses in the sheet which help counteract compressive stresses generated by material deformation; stresses that can result in unwanted wrinkling...

A systematic investigation was carried out to determine the optimum consolidation process conditions of a co-extruded polypropylene self-reinforced composite (SRC) considering its structural characteristics and static and time-dependent deformation behavior. It was observed that very little change in the processing condition influenced significantl...

This article describes a method of using both picture frame (PF) and bias extension (BE) tests together to characterize accurately the trellis shearing resistance of engineering fabrics under low in-plane tension conditions. Automated image analysis software has been developed to reduce the amount of laborious manual analysis required to interpret...

Textile composites made of woven fabrics have demonstrated excellent mechanical properties for the production of high specific-strength products. Research efforts in the woven fabric sheet forming are currently at a point where benchmarking will lead to major advances in understanding both the strengths and the limitations of existing experimental...

Biaxial Bias Extension tests have been performed on a plain-weave carbon fibre engineering fabric. The test results have been normalised using both the upper and lower bound method proposed by Potluri et al. and also using a novel alternative normalisation method based on energy arguments. The normalised results from both methods are compared and d...

This paper presents thermoforming experiments and FE simulations of a commingled glass-PP woven composite on a double dome geometry, with the aim of assessing the correspondence of predicted and experimental shear angles. Large local deformations - especially in-plane shear, i.e. relative rotation between the two yarn families – occur when draping...

Wrinkling often occurs during textile composite forming and is a major problem for manufacturers. The prediction of this defect is, therefore, of major importance for the design and optimization of textile composite structures. Numerical simulations of forming for textile composites over a hemisphere have been conducted using a rate/temperature-dep...

Normalisation methods for both Picture Frame (PF) and Bias Extension (BE) tests [1] on rate-independent compressible fabrics undergoing trellis shear are presented. Normalisation of PF test results is relatively straightforward and involves dividing the force results by a characteristic length. A normalisation procedure for BE test results has been...

In this study, FE simulations of the forming of viscous textile composite over a hemisphere and a helmet were conducted using a rate/temperature-dependent hybrid FE model in a commercial Finite Element code, Abaqus ExplicitTM. Optimum forming parameters such as the normal force distribution across the edges of a blank, blank size, forming temperatu...