Peter Myler

This study focuses on the deformation characteristics of hybrid orthotropic composite sandwich beams under axial and bending loading. The homogeneous cores of the hybrid orthotropic sandwich beams affect different parameters on structures. We followed by analytically determining effective material properties to study response of the hybrid sandwich beam under axial and bending loading. Ensuing, we programmed all steps and procedures of solution algorithm into commercially available MATLABTM 2020 code to simulate practical scenarios. Subsequently, we collected and processed data in tabular and graphical forms to facilitate analyses. We compared simulation generated results to the data results available in the literature and found to be within the acceptable range of (±6%) deviations. We observed that the hybrid structure beams had undergone less deformation that confirmed that the hybrid structure beams have comprehensive mechanical advantages as well as has high strength and specific energy absorption capabilities. Based on comparison of the results, the hybrid beams are more damage resistant and tolerant than beams made of the other type of materials. Since hybrid sandwich beams are relatively light, economical, and perform better under axial and bending deformations. Therefore, this study could also be extended to investigate performance of the orthotropic sandwich beam structures under multiple loading directions as well as proposes that the usage of the hybrid sandwich beam components will be useful in global structures.

Sandwich structures fabricated from an aluminium skinned foam enclosed within a carbon fibre reinforced composite structure have the potential application for high-performance on- and off-road automotive vehicles. The deformations and failure of these types of structures are presented, and results indicate that the application of aluminium face sheets with aluminium foam (AF) aids to prevent the delamination of the outer layers of carbon fibre reinforced polymers (CFRP). The load carrying capacity has been increased by utilising a manufacturing method to maintain the adhesion between the core and the skins until the failure stage is reached. The core shear and de-bonded issue associated with this type of sandwich structure can be addressed by this manufacture method. The peak average flexure load capacity of an aluminium foam sandwich structure (AFSS) with a completely wrapped around CFRP skin was 2800 N with a mass of 191 g. This compares favourably with previously used AFSS without the skins, which had a peak average load of 600 N and a mass of 125 g. An initial finite element model for comparison purposes has been developed to represent the structure’s behaviour and predict the associated failure loads. It is proposed that CFRP wrapped around AFSS enhances the structural performance without significant weight gain.

In thermoplastic composites, the polymeric matrix upon exposure to heat may melt, decompose and deform prior to burning, as opposed to the char-forming matrices of thermoset composites, which retain their shape until reaching a temperature at which decomposition and ignition occur.
In this work, a theoretical and numerical heat transfer model to simulate temperature variations during the melting, decomposition and early stages of burning of commonly used thermoplastic matrices is proposed. The scenario includes exposing polymeric slabs to one-sided radiant heat in a cone calorimeter with heat fluxes ranging from 15 to 35 kW/m2. A one-dimensional finite difference method based on the Stefan approach involving phase-changing and moving boundary conditions was developed by considering convective and radiative heat transfer at the exposed side of the polymer samples. The polymers chosen to experimentally validate the simulated results included polypropylene (PP), polyester (PET), and polyamide 6 (PA6). The predicted results match well with the experimental results

A novel laboratory scale testing equipment has been designed and developed, which combines impact and heat/fire conditions to enable the testing of composite laminates, including the ability to capture debris/particles released during the test. This incorporates a pendulum impactor to create impact whilst the sample is exposed to a cone heater at a particular heat flux for a specified period of time.
A protocol for testing samples under different conditions and capturing particles released, both from the front and back faces, along with effluents has been provided. A carbon fibre-reinforced epoxy composite was impacted whilst being exposed to different heat fluxes for a range of time periods. A loss of stiffness related to the heating exposure time was found to affect the damage type. At lower heat fluxes, the captured particles included broken carbon fibres, decomposed resinous particles and resin coated fibres. Quantitative and morphological analyses of captured particles demonstrated that the sizes of decomposed resin particles and fibres reduced with longer exposure time or increased heat flux. This information could be useful to provide insight into potential health hazards of components of the composites.

The effects of matrices from co-cured blends of an unsaturated polyester (UP) with inherently fire-retardant and char-forming phenolic resoles (PH) on the mechanical and fire performances of resultant glass fibre-reinforced composites have been investigated. Three different phenolic resoles with increasing order of compatibility with UP have been used. These are: (i) an ethanol soluble resin, (PH-S), (ii) an epoxy-functionalized resin (PH-Ep), and (iii) an allyl-functionalized resin (PH-Al). The mechanical properties of the composites increased with increasing compatibility with two resin types as might be expected, but not previously demonstrated. However, even with the least compatible resin (PH-S), the impact properties were unaffected and the flexural/tensile properties while reduced, were still acceptable for certain applications. Fire properties were however, in reverse order as previously observed in cast resin samples from these composites. Moreover, the reduction in flammability was less compared to those of the cast resin samples, reported previously, explained here based on the insulating effect of glass fibre reinforcement.

Objectives:
Conduct a comprehensive epidemiological study of match injury characteristics (incidence, severity, causes, diagnostics, and temporal trends) in professional rugby league.
Design:
Prospective cohort design.
Methods:
Data was captured over the 2013, '14, and '15 seasons, collected via an online-reporting survey tool, and underpinned by nominal group technique-agreed definitions. Injury details were provided by club medical staff in accordance to the survey fields from all European Super League teams (e.g. injury occurrence/return dates, diagnosis, mechanism, recurrence). All time-loss injuries have been reported.
Results:
Injury incidence of 57 injuries/1000h has been observed over the three-year period, with an average of 34days missed per injury. The final 20-min period was the most significant period for injury occurrence, and higher incidence of injury/1000h played was during the start of the season in February, although an absolute injury risk for injury frequency was shown in April due to the greatest playing time. Forward positions reported the highest injury incidence whilst tackle activities were the most frequent mechanism of injury. Concussions and hamstring strains (5 injuries/1000h) were the most commonly diagnosed injuries, although the knee joint region (10 injuries/1000h) was the most frequently injured area.
Conclusions:
In light of the most common injury diagnoses, mechanisms, identified seasonal risk, and time of match, the data should look to inform player preparation in terms of physical conditioning and tackle technique in order to optimise player welfare and availability for participation.

In engineering, prevention of failure of materials is of cardinal importance. Once failure can be predicted and anticipated fairly correctly, timely corrective measures can be taken to avert catastrophes. This way, costs would be reduced and profits maximized. Some of the difficult materials to predict the failure for are natural fibre reinforced composites due to the fact that fibres do not all fail at the same time with load value. Some fibres fail earlier than others, thereby exhibiting lesser failure values than theoretically calculated. In this research, polyester resin was reinforced with natural sisal using the hand lay-up process. Three types of reinforcement mats were used. Two were handmade while one was machine made. Composites of varying sisal volume fractions were made. Pressure of 15 – 20 bar was applied to the slates for 15 minutes before allowing them to cure at room temperature for 24 hours. Pressure was applied in order to eliminate air bubbles and also to ensure an even and flat resultant surface. Test specimens from the resultant composites were subjected to three-point and four-point bending to determine the Young's modulus, E. The results revealed that E values for all the composites were lower that what was theoretically calculated from the volume fractions; the hand-made mats resulted in lower E values than the machine-made mat; it was also observed that the higher the volume fraction, the higher the E value obtained experimentally.

This work is concerned with the dynamic computational modelling of fibre-reinforced laminated composite panels subjected to low velocity drop-weight impacts. Wings and fuselage of aircraft structures are prone to tool (box) drop impacts during normal shipping and handling of component assembly and maintenance services. Flat nose impacts inflict localised barely visible internal damage that severely reduce compressive residual strength and might result in catastrophic failure during future operations. Hence it is important to have a better understanding of the impact response of composites to mitigate the damage and avert the unexpected failures. Many reported works on the topic are experimental, based on quasi-static indentations that take longer than contact time, and produce global deformations of thin panel where short time effects and through-thickness stresses are neglected. Hence dynamic model is needed to investigate impact behaviour of thick panels for detailed information. The present computational model includes short time effects and utilise through-thickness stresses in mode-based failure criteria to differentiate ply-by-ply failure modes. Cases of laminates up to 7.6 mm thick impacted with flat and round (for comparisons) nose impactors were simulated using ABAQUS (TM)/Explicit dynamic routine. High stress concentration regions were meshed with adaptive meshing techniques using reduced integration elements. Selected simulation results were compared against experimental, intra-simulation results, and the data available in the literature and found to be in acceptable agreement. (C) 2016 Elsevier Ltd. All rights reserved.

The thermal barrier efficiency of two types of ceramic particle, glass flakes and aluminum titanate, dispersed on the surface of carbon-fiber epoxy composites, has been evaluated using a cone calorimeter at 35 and 50 kW/m2, in addition to temperature gradients through the samples’ thicknesses, measured by inserting thermocouples on the exposed and back surfaces during the cone tests. Two techniques of dispersing ceramic particles on the surface have been employed, one where particles were dispersed on semi-cured laminate and the other where their dispersion in a phenolic resin was applied on the laminate surface, using the same method as used previously for glass fiber composites. The morphology and durability of the coatings to water absorption, peeling, impact and flexural tension were also studied and compared with those previously reported for glass-fiber epoxy composites. With both methods, uniform coatings could be achieved, which were durable to peeling or water absorption with a minimal adverse effect on the mechanical properties of composites. While all these properties were comparable to those previously observed for glass fiber composites, the ceramic particles have seen to be more effective on this less flammable, carbon fiber composite substrate.

This work is concerned with the prediction of low velocity impact damage resistance of carbon fibre-reinforced laminated composite laminates. Pre-assumed damage induced laminates were simulated to correlate damage corresponding to impactor nose profiles. Majority of the existing studies conducted on the topic are experimental, based on three-dimensional stresses and failure theories that cannot readily predict ply level impact damage. Hence efficient computational models are required. The present study was conducted to efficiently predict ply level impact response of composite laminates. Static load-deflection based computational model was developed in the commercial software ABAQUS (TM). Eight, 16, and 24 ply laminates impacted by point, small, medium, and flat nose impactors were considered with emphasis on flat nose impacts. Loading areas under the impactor nose profiles were partitioned to investigate effects from variations in applied loading. Pre-assumed damage zones consisting of degraded material properties equivalent to the impactor nose profiles were inserted across thickness of the laminates to predict ply-by-ply damage. Impactor nose profiles and pre-assumed damage zones (size, type, and location) were correlated to the simulation produced deflection quantities to predict the ply level damage. Selected results were compared against the data available in the literature and also against the intra-simulation results and found in good agreement. (C) 2015 Elsevier Ltd. All rights reserved.