Experimental Study of Static and Fatigue Behavior of CFRP-Balsa Sandwiches under Three-point Flexural Loading

Abstract

Balsa wood is a natural cellular material with an excellent resistance-toweight ratio that is ideal for manufacturing the core of sandwich structures. In this study, sandwich specimens with a carbon-fiberreinforced polymer (CFRP) skin and a balsa wood core were tested with static and dynamic loading. Three-point flexural tests in static regime determined the mechanical characteristics of the CFRP-balsa specimens that were needed for subsequent fatigue strength tests. Also, experimental research was performed on the Charpy impact response of the CFRP-balsa sandwich specimens. This study implemented an accelerated fatigue testing method to identify and predict the mean fatigue life of the CFRP-balsa sandwich specimens subjected to cyclic fatigue via three-point flexural tests. Using the accelerated fatigue and the three-point flexural testing methodology on the CFRP-balsa sandwich specimens, the testing period was reduced by 11.9 times, and thus the material costs necessary for the tests were also reduced. Also, the breaking surfaces were analysed to reveal the failure modes of CFRP-balsa specimens subjected to static and fatigue tests at threepoint flexural and at impact tests.

Mechanical Performances of Lightweight Sandwich Structures Produced by Material Extrusion-Based Additive Manufacturing

“…When the core sandwich is thick enough, an indentation mode occurs firstly, but the sandwich structures will finally fail in a face yield failure mode (first phase), of the upper skin, under sufficient impact energy [ 31 ]. A second phase consists of the onset of the crack of the diamond core and the subsequent propagation of the crack to the lower skin [ 32 ]. The sandwich structures with corrugated core showed a debonding between the skin and the core mainly due to the small contact surface between them ( Figure 10 c).…”

Experimental and finite element analysis of the impact response of agglomerated cork and its intraply hybrid flax/basalt sandwich structures

“…Considering the severe susceptibility of sandwich structures to impact events many works concentrated on the dynamic response of these bio-based composites addressing their fatigue behavior with both synthetic fibers [27] and natural fibers [28] skins, the low velocity impact behavior in comparison with the one of more traditional PVC foams [29,30], the high strain rate behavior in compression [31], the ballistic response [32] and the residual properties after impact both in compression [33] and bending [34]. The comparison of low velocity impact response of balsa wood and PVC foams sandwich composites proposed by Atas and Sevim [30] demonstrated that for low energy impacts balsa wood structures are characterized by a higher bending stiffness that determines a lower deflection and a higher contact force.…”

Balsa Çekirdekli Sandviç Kompozitlerin Darbe Davranışlarının Deneysel Olarak İncelenmesi

“…Balsa çekirdekli yapılara ait hasar tiplerini belirlemiş ve S-N eğrilerini oluşturmuştur. Yapıya ait maksimum normal gerilme ve maksimum kayma gerilemelerini belirlemiştir [11]. Özdemir ve diğ., farklı çekirdek kalınlıklarındaki (15mm ve 20mm) balsa odunlarının kullanıldığı sandviç kompozitlere tekil ve tekrarlı düşük hızlı darbe deneyi uygulamıştır.…”