Title: Modified Short Beam Shear Testing Methodology for Pultruded Unidirectionally Reinforced Composite Rods

Authors: Yves Cordeau, Fayaz J. Ali, Dr. Lei Zhao, and Dr. Mac Puckett

DOI: 10.33599/nasampe/c.19.0734

Abstract: The Short Beam Shear (SBS) test is commonly run as a quality check on pultruded rods. It is easy to run and does not require much sample preparation for testing beyond cutting the rod to length. Although it is fairly simple to set up and run unidirectionally-reinforced composite rods (URCRs) in an SBS configuration (ASTM D4475)1, it can be very challenging to generate proper interlaminar shear stress (ILSS) failure modes2. The data presented in this paper demonstrates the difficulties of obtaining proper ILSS failure modes (horizontal shear) with composite rods using the traditional ASTM D4475 3-point loading test configuration (Figure 1). Undesirable testing artifacts (e.g. fiber buckling on the compression surface) are routinely observed when testing URCRs using the traditional ASTM D4475 configuration2. Failure that occurs via non-ideal pathways leads to artificially low ILSS values from 12-30% below achievable values depending on materials of construction and diameter of rods.

The data collected in this study demonstrate that the PolyOne Advanced Composites (PAC) modified SBS method (even though it is clearly outside of the specifications of ASTM D4475) provides an improved alternative for testing ILSS of pultruded rods. Additionally, the use of the modified method results in the samples failing with the correct failure modes (horizontal shear), and the absence of testing artifacts such as compression buckling and localized crushing of the URCRs (Figures 2,3,9,10,13,16, and 19).

Obtaining the correct failure modes in an SBS test has significant implications for testing in the pultrusion industry. One important implication is that producing the correct failure mode with the modified test method can be used to more effectively screen rods that have processing defects such as micro-voids, insufficient fiber wet-out, etc. The modified test method can be discriminatory, since any decline in shear-related properties can be attributed to the part and its processing, rather than testing artifacts.

References: 1. ASTM D-4475-02 Standard Test Method for Apparent Horizontal Shear Strength of Pultruded Reinforced Plastic Rods By the Short-Beam Method 2. Whitney, J.M., Browning, C.E., On short-beam shear tests for composite materials, Experimental Mechanics, Volume 25, Issue 3, 1985 3. Micelli, F., Nanni, A., Durability of FRP rods for concrete structures, Construction and Building Materials,Volume 18, Issue 7, 2004 4. Abali, F., Pora, A., & Shivakumar, K., Modified Short Beam Shear Test for Measurement of Interlaminar Shear Strength of Composites, Journal of Composite Materials, 37(5), 453–464, 2003

Conference: CAMX 2019

Publication Date: 2019/09/23

SKU: TP19-0734

Pages: 9

Price: $18.00