The effect of pin angle on the microstructure of resin-infused pin-reinforced metal-composite hybrid joints

Metal-composite hybrid joints with through-thickness pins are high-performing, but a study is needed on manufacturing resin-infused composites with large pin angles. Single-pin metal-composite joints were investigated with pin angles of 0°, 20°, 45° and 80°. Microstructural characterisation revealed the pin insertion zone varied significantly with the pin angle and along the pin length. With increasing pin angle, the diamond-like resin-rich zone became triangular, asymmetric, and significantly reduced in size to effectively zero. Other asymmetric, complex and novel features were observed as well. Despite these features, the joints had suitably high quality and demonstrated the potential of resin-infused composites for high pin-angle joints

Collapse Analysis, Defect Sensitivity and Load Paths

An experimental program for collapse of curved stiffened composite shell structures encountered a wide range of initial and deep buckling mode shapes. This paper presents work to determine the significance of the buckling deformations for determining the final collapse loads and to understand the source of the variation. A finite element analysis is applied to predict growth of damage that causes the disbonding of stiffeners and defines a load displacement curve to final collapse. The variability in material properties and geometry is then investigated to identify a range of buckling modes and development of deep postbuckling deformation encountered in the experimental program. Finally the load paths for the damaged panels are used to visualise the load transfer and enhance the physical understanding of the load displacement history

A finite element methodology for analysing degradation and collapse in postbuckling composite aerospace structures

A methodology for analysing the degradation and collapse in postbuckling composite structures is proposed. One aspect of the methodology predicts the initiation of interlaminar damage using a strength criterion applied with a globallocal analysis technique. A separate approach represents the growth of a pre-existing interlaminar damage region with user-defined multi-point constraints that are controlled based on the Virtual Crack Closure Technique. Another aspect of the approach is a degradation model for in-plane ply damage mechanisms of fiber fracture, matrix cracking, and fiber-matrix shear. The complete analysis methodology was compared to experimental results for two fuselage-representative composite panels tested to collapse. For both panels, the behavior and structural collapse were accurately captured, and the analysis methodology provided detailed information on the development and interaction of the various damage mechanisms

Experimental response of high strength steels to localised blast loading

Modern high-strength and armour grade steels have developed continually increasing strength and fracture toughness, but there have been limited experimental investigations into their response to localised blast response. In this work, the response of four modern steels to localised blast loading is experimentally investigated. The deformation and rupture threshold is comprehensively characterised and a detailed fractographic investigation is conducted into the initiation and progression of rupture failure modes. It was found that for the current experimental setup, higher strength steels can outperform more ductile steels, and that steel with a tailored microstructure had a higher rupture threshold than three modern armour steels. All steels studied herein initiate rupture via ductile shear fracture, as opposed to tensile tearing which is common in lower-strength steels. Results showed that the deformation resistance cannot be predicted precisely using only yield strength, and only by considering strain hardening can the deflection response be more accurately predicted. A new non-dimensional impulse correction parameter was also developed that captures the effect of charge stand-off on the target plate deformation and rupture performance. The results demonstrate the suitability of high-strength steels for blast applications, and have application to the design and analysis of safer armour systems for blast protection