Characterisation of 'class A' polymer composites for the automotive industry

This thesis addresses problems associated with surface quality measurement and residual volatile organic compounds for composite laminates intended for use as cosmetic body parts based on unsaturated polyester resin containing shrinkage control additives. Surface quality measurement techniques were compared for composite laminates allowing for rapid characterisation and benchmarked to industrial standards. Thermal desorption and solvent elution techniques were used for the detection of residual volatiles with styrene and benzaldehyde being the main focus. The degree of conversion and residual volatiles were monitored for three peroxide initiators via a series of statistically developed experiments. This work highlighted the need for alternative shrinkage control methods. A novel approach was studied through the use of nano-scale silicates. An exfoliation process was developed with subsequent characterisation of thermal and mechanical properties for the nanocomposite. Finally, a series of hybrid matrices consisting of nanocomposite and low profile additive blends were monitored for effects on surface roughness, residual volatile levels and mechanical performance

Modelling flexural performance of hollow pultruded FRP profiles

Hollow Pultruded Fibre-Reinforced Polymer (PFRP) profiles, as novel construction material, require further development of design tool to broaden the applications. This paper proposes a combined experimental and numerical methodology as a design tool to investigate the failure modes of these profiles under four-point bending. Two different profiles, each with 10 samples, were tested until failure and were used to validate the numerical model. A finite element model was built based on a fast-convergence incremental approach that suits flexural loading and reduces the computational cost. The validated model was used to study the failure sequence thoroughly and perform an extensive parametric study on the design parameters. Each geometric parameter was studied individually first to determine the relevant levels for each parameter in the full factorial study. A full factorial design of experiment was used to capture the critical parametric interactions with over 81 numerical models. The design rules and recommendation were established for the optimal flexural behaviour of hollow box PFRP profiles to withstand local buckling of the top flange

Self-healing polymers: Synthesis methods and applications

Clays have numerous applications in a variety of applications including engineering, medical and civil areas. The wide applicability of clays is attributed to their useful physico-mechanical as well as biomedical applications, since they are readily available, nontoxic to human body and environment, low cost and having kneading, swelling, adsorption of properties for metal ions. Industrial sectors in different fields are greatly dependent on the usage of different clays, but the cracks or defects or damaged areas present in clays restrict their practical applications. In order to overcome these problems, various polymeric materials have been developed through different strategies to heal the cracks or repair the damaged areas of clays, and improve their properties and potential usage in various applications. This review will address several aspects such as preparation, structure–property relationships, properties of different types of clays and self-healing polymers, healing process of cracks in clays using polymers, crack healing mechanism, test methods of healing efficiency, properties (e.g. structure, hydraulic conductivity, swelling nature, mechanical and rheology) of clays before and after healing of cracks, and their applications

Testing and modelling the fatigue behaviour of GFRP composites – Effect of stress level, stress concentration and frequency

The effects of stress level, stress concentration and frequency on the fatigue life of glass fibre reinforced polymer (GFRP) composites have been investigated under tension-tension fatigue at a stress ratio of 0.1. Vinyl ester-based GFRP laminates were tested at a stress level of 80%, 70%, 60%, 50%, 40% and 25% of the ultimate tensile strength until the failure or up to 8 million cycles whichever comes first in order to determine fatigue life and identify failure modes. The results showed that the composites failed in pure tension at high applied stress while the failure was dominated by stress concentration at low stress level. Moreover, stress concentration was found to reduce the fatigue life of the laminated composites and the test frequency of up to 8 Hz did not induce excessive self-heating. The mean stress failure criteria was found appropriate for numerical modelling of GFRP composites subjected to low level of stress while Goodman failure criteria is suitable at high stress condition. The analytical model considering the effect of stress ratio, applied maximum stress, frequency and material properties is able to predict reliably the fatigue life of GFRP composites in tension

Controlling mass loss from RTM6 epoxy resin under simulated vacuum infusion conditions

A certified aerospace resin (RTM 6) normally utilised for resin transfer moulding is considered for vacuum infusion. The resin was subjected to simulated vacuum infusion conditions by using a specialised thermogravimetric analysis that enables control of pressure as well as temperature. By varying conditions, it was possible to investigate the expected occurrence of volatile loses during infusion that could cause mechanical or cosmetic defects in a part. With particular reference to RTM6, it was determined that full vacuum could be used for infusion provided that the temperature was kept below ∼130 °C. Higher temperatures could be used, but the applied vacuum should be significantly reduced. Of note is that the manufacturers datasheet recommends processing parameters that could result in volatile loss. As such, the pressure enhanced TGA method may be considered more widely for providing processing conditions supplemental to the manufacturers recommendation for any liquid resin used under vacuum conditions

Modelling VARTM process induced variations on bending performance of composite Omega beams

Finite element simulation with cohesive contact is presented, to correlate the vacuum assisted RTM process and the bending performance of Omega beams. The model considers the process induced variations, including part thickness, resin rich pockets and voids. The bending performance prediction relies on cohesive contact to model delamination initiation and propagation. Computing efficiency is achieved by mesh scaling. The modelling approach applies to three variations of Omega beams with the different mode-mixture ratios. The finite element predictions result in a high degree of agreement with the experimental measurements

Evaluation of cure shrinkage measurement techniques for thermosetting resins

Resin chemical shrinkage dictates the surface integrity and the roughness of a composite structure. Thus, to minimize surface failures and to produce a good surface quality it is a requisite to be able to measure and track resin shrinkage during the cure process. This manuscript investigates and evaluates the measuring and monitoring of real-time resin shrinkage using a rheometer, a helium-based pycnometer and a thermo-mechanical analyzer (TMA) for ambient curing UP and epoxy resins. Shrinkage readings obtained from the newly developed robust technique with the rheometer concur well with readings from the traditional pycnometric method. They also coincide within the accepted literature values of 7–10% and 3.5–4.5% for the UP and epoxy systems, respectively. Shrinkage measurements during post-cure were effectively carried out at an elevated temperature, suggesting that the methodology provided can be applied to non-ambient curing systems. The TMA was found to be unsuccessful in measuring shrinkage reliably

Characterisation of 'class A' polymer composites for the automotive industry

This thesis addresses problems associated with surface quality measurement and residual volatile organic compounds for composite laminates intended for use as cosmetic body parts based on unsaturated polyester resin containing shrinkage control additives. Surface quality measurement techniques were compared for composite laminates allowing for rapid characterisation and benchmarked to industrial standards. Thermal desorption and solvent elution techniques were used for the detection of residual volatiles with styrene and benzaldehyde being the main focus. The degree of conversion and residual volatiles were monitored for three peroxide initiators via a series of statistically developed experiments. This work highlighted the need for alternative shrinkage control methods. A novel approach was studied through the use of nano-scale silicates. An exfoliation process was developed with subsequent characterisation of thermal and mechanical properties for the nanocomposite. Finally, a series of hybrid matrices consisting of nanocomposite and low profile additive blends were monitored for effects on surface roughness, residual volatile levels and mechanical performance.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Wind Turbine Blade Design

A detailed review of the current state-of-art for wind turbine blade design is presented, including theoretical maximum efficiency, propulsion, practical efficiency, HAWT blade design, and blade loads. The review provides a complete picture of wind turbine blade design and shows the dominance of modern turbines almost exclusive use of horizontal axis rotors. The aerodynamic design principles for a modern wind turbine blade are detailed, including blade plan shape/quantity, aerofoil selection and optimal attack angles. A detailed review of design loads on wind turbine blades is offered, describing aerodynamic, gravitational, centrifugal, gyroscopic and operational conditions