Static behaviour of preconditioned glass-fibre-reinforced epoxy sandwich I-beams

• Published in: Composites science and technology Vol. 59; no. 6; pp. 963 - 973
• Main Authors: Zhou, G., Forbes, A.J., Foster, N.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-01-1999; Elsevier
• Subjects: A. Polymer-matrix composites; Applied sciences; B. Strength; C. Deformation; C. Sandwich; Exact sciences and technology; Forms of application and semi-finished materials; Laminates; Polymer industry, paints, wood; Static mechanical behaviour; Technology of polymers; B. Strength; Static mechanical behaviour; A. Polymer-matrix composites; C. Deformation; C. Sandwich; Polyimide; Laminate; Stress strain relation; Unidirectional fiber material; Fiber reinforced material; Sandwich structure; Mechanical properties; Epoxy resin; Shear strength; Experimental study; Composite material; Static load; Bending strength; Glass fiber fabric; Foam(plastics); Methacrylic derivative polymer; Woven material; Delamination; Fracture mode; Damaging
• ISSN: 0266-3538; 1879-1050
• DOI: 10.1016/S0266-3538(98)00136-5

The short-term mechanical behaviour of both intact and preconditioned glass-fibre-reinforced composite sandwich I-beams has been investigated under quasi-static loading. A high-strength and tough epoxy adhesive system has been used for bonding the flanges to the web section in the manufacturing of the I-beams. Preconditions included both appreciable bonding defects such as voids and debonds and barely visible impact damage (BVID). While voids and debonds with selected sizes and locations were introduced at the flange-web intersections directly associated with bonding, BVID was inflicted on the flange surfaces. It is found that halfway towards the peak load, the anti-symmetric buckling of the compressive flange occurs leading to some limited non-linear behaviour and that its associated edge delaminations at the compressive flange-web intersection are isolated and make no direct contribution to the ultimate failure of these I-beams. It is shown that the ultimate failure starts from the shear failure of the foam core in the sandwich web instead and ends with web skin wrinkling. It is demonstrated that under the current conditions, preconditions do not have an over-riding effect on the mechanical behaviour of I-beams and that the epoxy adhesive system is completely adequate.