In this paper, cure monitoring of a composite laminate is conducted, followed by subsequent structural health monitoring (SHM). A distributed optical fibre (DOF) sensor was embedded between glass fibre fabric plies during manufacture; part of the DOF length was micro-braided using glass fibres, while the remaining length was left 'bare' (as-received condition). In situ and real-time strain measurement during the infusion and curing processes of the laminate was completed. Cure monitoring of composite materials using different fibre orientations, sensor locations, raw materials, and manufacturing methods has been widely studied. However, no consensus was reached due to differences in raw materials, temperature profile, manufacturing method, fibre orientation, and sensor location. The manufactured composite plate was then subjected to repeated loading during a quasi-static four-point bending test, and the strain development along the length of the DOF was recorded. Comparable results were obtained from the micro-braided and bare sections of the DOF, showing the suitability of micro-braided optical fibres for real-time strain monitoring in composite structures. The micro-braiding DOF facilitates handling for automated manufacturing methods and can be used to follow the full life cycle of a composite from fabrication till end-of-life.

The increasing demands in subsea industry such as oil and gas, led to a rapidly growing need for the use of advanced, high performance, lightweight materials such as composite materials. E-glass fibre laminated pre-preg, filament wound and braided tubes were tested to destruction under hydrostatic external pressure in order to study their buckling and crushing behaviour. Different fibre architectures and wind angles were tested at a range of wall thicknesses highlighting the advantage that hoop reinforcement offers. The experimental results were compared with theoretical predictions obtained from classic laminate theory and finite element analysis (ABAQUS) based on the principal that the predominant failure mode was buckling. SEM analysis was further performed to investigate the resulting failure mechanisms, indicating that the failure mechanisms can be more complex with a variety of observed modes taking place such as fibre fracture, delamination and fibre-matrix interface failure.

Exper긮ऀmental behav긮ऀour of bolted jo긮ऀnts 긮ऀn tr긮ऀax긮ऀal bra긮ऀded (0°/±45°) carbon f긮ऀbre/epoxy compos긮ऀte lam긮ऀnates w긮ऀth dr긮ऀlled and moulded 긮ऀn fastener holes has been 긮ऀnvest긮ऀgated 긮ऀn th긮ऀs paper. Bra긮ऀded lam긮ऀnates were manufactured by vacuum 긮ऀnfus긮ऀon process us긮ऀng 12 K T700S carbon f긮ऀbres (for b긮ऀas and ax긮ऀal tows) and Arald긮ऀte LY 564 epoxy res긮ऀn. Moulded 긮ऀn fastener holes were formed us긮ऀng gu긮ऀde p긮ऀns wh긮ऀch were 긮ऀnserted 긮ऀn the bra긮ऀded structure pr긮ऀor to the vacuum 긮ऀnfus긮ऀon process. The damage mechan긮ऀsm of the spec긮ऀmens was 긮ऀnvest긮ऀgated us긮ऀng ultrason긮ऀc C Scan techn긮ऀque. The spec긮ऀmens were d긮ऀmens긮ऀoned to obta긮ऀn a bear긮ऀng mode of fa긮ऀlure. The bear긮ऀng strength of the spec긮ऀmens w긮ऀth moulded 긮ऀn hole was reduced 긮ऀn compar긮ऀson to the spec긮ऀmens w긮ऀth dr긮ऀlled hole, due to the 긮ऀncreased f긮ऀbre m긮ऀsal긮ऀgnment angle follow긮ऀng the p긮ऀn 긮ऀnsert긮ऀon procedure. An 긮ऀmprovement on the bear긮ऀng strength of moulded 긮ऀn hole spec긮ऀmens m긮ऀght be developed 긮ऀf the spec긮ऀmen d긮ऀmens긮ऀons would be prepared for a net tens긮ऀon mode of fa긮ऀlure where the f긮ऀbre m긮ऀsal긮ऀgnment would not have an effect as s긮ऀgn긮ऀf긮ऀcant as 긮ऀn the case of bear긮ऀng fa긮ऀlure mode, but th긮ऀs mode should be avo긮ऀded s긮ऀnce 긮ऀt leads to sudden catastroph긮ऀc fa긮ऀlures.

No abstract

Tailored fibre placement (TFP) is an embroidery-based technology that allows the fibre tows to be placed exactly where they are most needed for structural performance and stitched into position on a compatible textile or polymer substrate. In this study commingled carbon-nylon fibre tows were utilised to produce thermoplastic cross-ply net-shaped preforms using TFP. Four TFP composite plaques were manufactured; baseline (blank), machined-hole, tailored-hole-1 and tailored-hole-2. Steering the tows was used to create the hole in tailoredhole-1 and tailored-hole-2. In comparison to the design of tailored-hole-1, a different fibre trajectory, with a circular reinforcement around the hole, was suggested for the tailored-hole-2. Fibre volume fraction, optical microscopy, X-ray-CT scans, tensile and open-hole tests were carried out. With the exception of the baseline sample, the modified design of tailored-hole-2 composite exhibited the highest axial strength and modulus compared to the machined-hole and tailored-hole-1 composites. Only the tailored-hole-2 specimens exhibited less than 10% reduction of the notched strength compared to the un-notched strength. This study highlights the importance of the stress/load-paths and associated fibre-orientations. While TFP can be an extremely valuable design tool for composite preforms and resulting structural components, a deep understanding of stress distributions is inevitable to achieve optimal TFP-design.