Modified Short Beam Shear Test for Measurement of Interlaminar Shear Strength of Composites

Abstract

A modified short beam shear test was proposed to measure interlaminar shear strength (ILSS) of fiber reinforced carbon-carbon composites (CCC). The direct loading in the short beam shear (SBS) test is replaced by an indirect loading through a rubber pad and an aluminum seat. This loading reduced flexure stresses to less than one fourth of the SBS test and eliminated transverse shear stress concentration under the load point. Both beam and contact finite element analyses were conducted to validate the proposed method. The finite element analysis showed that the ILSS calculated from beam equation overestimates the strength by 5% for shear flexible composites. This reduction was found to be the same for both polymeric and carbon matrix composites. The test data confirmed the interlaminar shear failure and very low data scatter in measured strength. The measured ILSS of T300 CCC was 2.68 ksi and it is one of the highest values reported in literature.

Monotonic and cyclic short beam shear response of 3D woven composites

“…Three main types of damage modes were identified in each of the four composite architectures; localized damage beneath the punch, tow cracks along the bottom of the specimen, and delamination between the various tows and yarns. The localized damage is caused by the large stress concentration just beneath the central punch [20] resulting in crushing of the matrix and fiber damage in the tows. A tensile stress is generated at the bottom of the specimen due to the bending moment.…”

“…To reduce this contact stress and create a more uniform load distribution, four-point [17] bending and five-point [19] bending fixtures have been adopted. Other limitations to the use of SBS testing include a greatly underestimated ILSS of the material [17,20,21] due to the simplified assumption of shear flow equations which neglect the effect of concentrated load. Despite these disadvantages, SBS continues to be a useful test for qualitative comparison of the behavior of different material architectures as well as for quality control [17,20].…”

“…Other limitations to the use of SBS testing include a greatly underestimated ILSS of the material [17,20,21] due to the simplified assumption of shear flow equations which neglect the effect of concentrated load. Despite these disadvantages, SBS continues to be a useful test for qualitative comparison of the behavior of different material architectures as well as for quality control [17,20]. Short beam shear testing may also be used in the study of impact behavior of composites.…”

Impact of hybrid reinforcement (nano- and macro-) over quasi- isotropic symmetrically designed GFRP composites on short beam strength properties

“…Traulis et al [6] found that using z-pins, ILSS increased fairly. However, Abate et al [7] have reported that these techniques are labor intensive and require additional manufacturing processes that can significantly increase the cost of resulting component. Many researchers have explored other ways to improve ILSS by using nano, micro and macro fillers such as carbon nanotubes, graphene, micro Al2O3, SiO2, Ti2O3, short carbon fibers etc.…”

Analyzing Variation in ILSS of Fiber Reinforced Polymer Laminates with respect to Pressure variation in autoclave

“…Akay et al [2] noticed the degradation of matrix and hence decrease in ILSS property of carbon fiber reinforced bismaleimide on long term exposure to high temperature. Abali et al [3] had modified short beam shear test for measurement of inter-laminar shear strength of composites. Reddy et al [4] conducted experiments to find the flexural, compressive and ILSS properties of Kapok/ Glass composite.…”