In this study, the diameter of polyvinyl butyral nanofibers was modeled using response surface method based on three variables, at three levels of central composite design and particle swarm optimization-least squares support vector machine. Under optimal conditions, the measured mean diameter of the nanofibers was 175 nm. Sensitivity analysis in both models showed that polyvinyl butyral concentration in the solution was found to be the most effective parameter on the nanofiber diameter. The voltage is placed in the next. Fracture toughness under Mode I condition shows that the use of electrospun nanowebs as an interlayer in the structure of multi-layers composite has a positive effect on the GIc which values for the oriented and random nanofibers modified samples increased by 60% and 55%, respectively. According to SEM images, the main mechanism of fracture toughness in these samples was crack deflection and nanofibers crack bridging.

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In this research, Polyvinyl butyral (PVB) nanofiber as an interlaminar toughener was used in two autoclave and out-of-autoclave (OoA) curing processes in which the effect of curing method on the ability of nanofiber toughening and effectiveness of nanofiber to improve fracture properties of OoA-made structures were studied. For these investigations, PVB nanoweb was placed on mid plans of laminates and cured with the vacuum bag and the autoclave processing which were subsequently subjected to double cantilever beam (DCB) and end-notch flexure (ENF) tests. It was found that PVB nanoweb with the thickness of [Formula: see text] and nanofiber diameter of 158.6[Formula: see text]nm could increase mode-I fracture toughness ([Formula: see text]) 164% and 89% and mode-II fracture toughness ([Formula: see text] 58% and 62% for autoclave and out-of-autoclave-made specimens in comparison with their non-modified samples, respectively. This research also proved PVB nanofiber has the capacity to improve 16% and 10% [Formula: see text] and [Formula: see text] of OoA-made sample compared to the non-modified autoclave-made samples. So, we could conclude modified OoA-made laminated composite is a truly suitable replacement choice for autoclave-made glass–phenolic composites.