The design of reliable and efficient mechanical joints with non-crimp fabric (NCF) composites depends on several factors but knowledge on actual loading direction and an accurate compressive strength prediction is essential. Motivated by this, the current study is focused on the compressive strength of cross-ply NCF composites and the influence of fibre orientation in relation to the loading direction. Possible influence of stacking sequence on the compressive strength is also studied. Compression tests of cross-ply NCF composite laminates that are loaded at various off-axis angles are performed and the failure mechanisms are identified. An analytical semi-laminar based model for strength prediction of NCF composite laminates loaded in compression is then suggested. The model take in- and out-of-plane bundle waviness into account. Good agreement between the proposed model and experiments is observed.

The current study is focused on the compressive strength of composite materials containing non-crimp fabric (NCF) reinforcement, and how ply stacking sequence and fibre waviness influence onset and growth of damage in such materials. Experiments reveal significant effects from stacking sequence, both on the compressive strength as such, and on the underlying failure mechanisms. The fibre waviness also has a strong influence on the strength. Fibre kinking is seen before ultimate failure for all configurations but some of them also show local delamination prior to kinking. A finite element simulation methodology is developed and used for the studied cases. It handles local variations of fibre orientations by corresponding re-orientation of stiffness matrices at element level. The simulations provide good predictions of intra- and inter-laminar failure considering both in- plane and out-of-plane fibre bundle waviness. The model is further used in a parametric study of the influence from bundle waviness on the compressive strength.

The current study focuses on the bearing failure process of NCF composites and associated damage mechanisms. A set of experiments on bolted joints between NCF composite and steel plates have been performed. The bearing damage onset and failure progression in the composite was monitored at different load levels by microscopic image analysis. Fibre kinking in 0° layers was found as the key damage mechanism that initiate and drive the bearing failure. Matrix cracking and delaminations were found present as well. A cost-effective FE model that predicts bolt bearing failure of NCF composites was proposed.The model utilises state-of-the-art failure criteria and predicts both intra- and inter-laminar progressive damage. A good correlation between the predicted damage development process and experiments was observed both in terms of failure modes and load levels.

The study is focused on the bearing failure of NCF composites. The study presents a cost-effective methodology for high-fidelity meso-scale modelling of NCF composites and bearing failure prediction. The proposed methodology does not require expensive measurements of the meso-structure, nor access to specimen of the material. Instead, the complex meso-structural geometry in the model is achieved by the included compaction analysis of a dry multi-layer NCF preform. The modelling process is assisted by the developed Python-based automated framework. The methodology was applied to predict bearing failure of the experimentally tested pin-loaded quasi-isotropic NCF composites. A good agreement of the predicted and measured meso-structural geometry was found. The proposed method could accurately predicted the meso-structural geometry of the manufactured NCF composite in terms of both tow paths and their cross sectional shapes. The predicted bearingfailure response was found to be in general agreement with experiments. However, predictions of damage initiation and progression were too conservative. This is explained by the conservatism of the material properties used and material model.