Fibre reinforced composites in aircraft construction

A review of experimental data and elementary theoretical formulas for compressive failure of polymer matrix fibre composites indicates that the dominant failure mode is by plastic kinking. Initial local fibre misalignment plays a central role in the plastic kinking process. Theoretical analyses and numerical results for compressive kinking are presented, encompassing effects of strain-hardening, kink inclination, and applied shear stress. The assumption of rigid fibres is assessed critically, and the legitimacy of its use for polymer matrix composites is established.

http://www-mech.eng.cam.ac.uk/profiles/fleck/papers/38.pdf

Compressive failure of fibre composites

Fracture toughness of the tensile and compressive fibre failure modes in laminated composites

A review of the investigations that have been made on the stress and strength analysis of mechanically fastened joints in fibre-reinforced plastics (FRP) is presented. The experimental observations of the effects of joint geometry, ply-orientation, lay-up and through-thickness pressure on the joint behaviour are described briefly for both single and multi-fastener joints. The analytical and numerical methods of stress analysis required before trying to predict failure are discussed. The numerical approaches cover both two and three-dimensional models and the effects of clearance, friction and geometry are assessed. The several methods that have been used to predict failure in single or multi-fastener joints are described. It is concluded that there are some issues that require further investigation. There is no general agreement about the method that should be used to predict failure, but progressive damage models are quite promising since important aspects of the joint's behaviour can be modelled using this approach. In order to take into consideration several factors related to joint strength the use of three-dimensional models is suggested. These models require a three-dimensional failure criterion and an appropriate property degradation law.

/pdf/stress-analysis-and-strength-prediction-of-mechanically-4cv61eyfu5.pdf

Stress analysis and strength prediction of mechanically fastened joints in FRP: A review

Compressive Failure of Fiber Composites

We present an investigation into the compressive fracture properties of carbon fibre/epoxy laminates. Unnotched and notched strengths are reported for a wide range of ‘lay-ups’, and results are interpreted in terms of existing theories of strength. In all cases, we find that compressive failure is governed by plastic microbuckling of the 0° plies. For unnotched laminates, the failure strain is independent of lay-up configuration, suggesting that a critical strain to failure, or maximum strain criterion can predict the failure point adequately. In tests on notched panels, the growth of damage from the edge of a single hole is examined. For notched materials, the failure strength and damage zone size at failure support the prediction of the Soutis, Fleck and Smith model.

Compressive failure of notched carbon fibre composites

The effect of fiber architecture upon the compressive failure mechanisms is investigated for a wide range of fiber composites. Compressive tests are performed on both notched and unnotched specimens made from T800 carbon fiber-924C epoxy laminates, AS4 carbon fiber-PEEK laminates, 2D woven T800 carbon fiber-924 epoxy, and 3D woven AS4 carbon fiber-LY564 epoxy. Additionally, unnotched and notched compressive tests are performed on beechwood and birch plywood. In all cases, the dominant failure mechanism is by fiber microbuckling. An infinite band kinking model is used to estimate the unnotched strength and a large-scale crack bridging analysis is used to predict the notched strength.

PT Curtis

Papers

Compressive failure of notched carbon fibre composites

Compressive Failure of Laminated and Woven Composites

Hole-hole interaction in carbon fibre/epoxy laminates under uniaxial compression

Composite compressive strength modeller, version 1.4