Experimental and numerical determination of mode II fracture toughness of woven composites verified through unidirectional composite test data

Abstract

Due to the increase in prevalence of fibre-reinforced polymer matrix composites (FRPMC) in aircraft structures, the need for adaption of failure prediction tools such as fatigue spectra has become more pertinent. Fracture toughness is an important measure with regard to fatigue, while adequate techniques and an ASTM standard for unidirectional FRPMC exist, there are mixed opinions when investigating woven FRPMC. This study describes a three-dimensional finite element model developed to assist in determining the mode II interlaminar fracture toughness ( G IIc) of fibre-reinforced woven composites, validated by an experimental and numerical comparison of G IIc determination for unidirectional FRPMC. Experimental testing mirroring the ASTM D7905 resulted in a measure of 1176 J m−2 for the unidirectional specimen, while comparisons made with the literature achieved an average value of 1459.24 J m−2 or the woven specimen. Three numerical methods were employed due to their prominence in the literature: displacement field, virtual crack closure techniques and the J integral. Both the J integral and the displacement field three-dimensional models produced satisfactory unidirectional G IIc estimates of 1284 and 1116.8 J m−2, respectively. Displacement field had a 5% uncertainty in G IIc when compared with experimental results, while J integral had an approximately 8.5% uncertainty. Extending the analysis to the woven specimens, values of 1302.8 and 1465.3 J m−2 were obtained from J integral and displacement field methods, respectively, both within 10% of the experimental values. Hence, numerically determined unidirectional G IIc values were verified with experimental results, leading to the successful employment and extension to woven composites which displayed similar agreement.

Study of mode II interlaminar fracture toughness of laminated composites of glass and jute fibres in epoxy for structural applications

“…Interlaminar shear, strain and grid breakage, by and large, are the basis of internal delamination. The good agreement between experimental and theoretical crack sturdiness data means that the SIGMASOFT program can be used to model the fibre content and arrangement to give good break resistance in hybrid shaped long glass fibre reinforced thermoplastics [27][28][29][30][31][32][33].…”