Abstract
Thin-walled fibre reinforced composites like carbon fibre reinforced plastics are very susceptible to strength reductions due to low-velocity impact damages. In aerospace engineering, the dominating failure mechanisms of impact damaged composite structures are usually investigated based on the compression after impact (CAI) test procedure. This enables the determination of the influence of impact damages on the static residual compressive strength. CAI testing procedures are typically applicable to composite plates with thicknesses larger than 3–4 mm. If thinner panels are used, they typically fail near one of the loaded edges of the CAI device, in particular the area of the free edge (which is needed for compressing the panel) and not within the free measuring area. As a consequence, the investigated samples cannot be used as valid tests for the evaluation of the residual strength in CAI testing. In order to enable an investigation of the residual strength of thin-walled plates in CAI testing, a CAI testing device is developed based on an available CAI fixture and a standardized one. For comparability reasons, this new device exhibits the same dimensions as standardized fixtures. It shows a significant improvement with respect to standardized devices concerning the measurement of mechanical behaviour during CAI testing.
Highlights
Due to their high specific strength and stiffness, fibre reinforced composites like carbon fibre reinforced plastics (CFRP) are increasingly being used in a wide variety of industries
The influence on the residual strength is typically investigated based on the compression after impact (CAI) test procedure
It enables the determination of the influence of impact damages on the static residual compressive strength
Summary
Due to their high specific strength and stiffness, fibre reinforced composites like carbon fibre reinforced plastics (CFRP) are increasingly being used in a wide variety of industries. The supports of the CAI samples have been revised in such a way that the best possible visibility of the entire free measuring area is ensured This is due to the fact that for an investigation of the interaction between global buckling and local failure due to impact damages, the entire free measurement area is ideally visible to digital image correlation (DIC) technology. In the context of this article, a modified CAI test device based on the experimental device according to Linke and García-Manrique [18] is further developed and designed in order to fulfil the previously mentioned requirements such as same plate dimensions as well as same free measuring area like standard devices and good visibility of the measuring area (a detailed list of all requirements can be found in [19]). The conceptual contents of this solution variant are used and implemented within the design process
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