How to relate compressive strengths of multi-directional laminates to fundamental unidirectional material strength?

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Over recent years, fibre-reinforced polymers (FRP) have demonstrated excellent in-plane tensile properties and are used in aerospace, automotive, and energy applications due to their significant weight reduction. However, in-plane compressive properties are 40% lower on average than that of tensile properties. The compressive performance of FRP hasn't been well understood due to the challenges of identifying the materials' true compressive strengths. Fundamental compressive tests of composites show inconsistency of results as fibre instability can lead to structural failure. Further research on the compressive performance of composites is required to utilize FRP materials in further applications. This research project is supported by EPSRC and contributes to the objectives of NextCOMP for the next generation of fibre-reinforced composites to develop novel composite materials that can endure higher compressive load-carrying capability. The development of composite compressive properties can lead to further industrial utilization of composites in compressive applications. A review of naturally occurring composite structures will be used to inspire new techniques to design and manufacture advanced composites with novel architecture.The aim of this PhD project is to improve the compressive performance of composite materials. - Experimental procedures must be reviewed and improved to obtain a higher compressive failure strain of FRP materials than those reported.- Development of finite element analysis (FEA) models to validate experimental results. The model results would be used to predict the compressive performance of FRP materials using different architectures.- Validate new architectures of composite materials to improve the in-plane compressive performance of composite structures.- Design, manufacture, test, and analyse complex hierarchical architecture that results in improved compressive properties of composite materials.The key objectives for this project can be summarised as follows: - Review the effects of stacking sequence to identify new techniques that can support longitudinally loaded fibres in compression.- Assess current compressive test methods to identify suitable experimental procedures for compressive failure within composite laminates. - Investigate methods for fibre stability in compression through the reduction of fibre misalignment.- Overwound / overbraid architectures to delay kink band initiation.- Use of pultruded rod architecture to embed into current laminate architecture. - Monitor uni-directional material stability and its improvement with the use of hybrid composites. The research would support the purpose of identifying and improving the compressive performance of uni-directional FRP materials. This would increase the use of FRP structures in further engineering applications, in particular the aerospace and civil engineering sector. The traditional materials used are expensive to transport and can cause further risks to employees. FRP structures would re-innovate the current structures to allow for the manufacturing of portable lightweight structures with improved corrosion resistance properties. The development of novel composite architectures from natural composite architectures and current compressive enduring structures will lead to identifying techniques to improve the compressive properties of FRP materials.