Acoustic Emission from Microcrack Initiation in Polymer Matrix Composites in Short Beam Shear Test

Abstract

Acoustic emission (AE) was applied for detection of microcrack initiation in carbon fiber reinforced polymer composites subjected to shear stresses. Experimental materials were prepared from polyester bonded unidirectional (1D) non-crimp fabric and 2D plain-weave carbon fiber fabrics, using the resin transfer moulding technology. Control of epoxy resin/carbon textile proportions enabled variation of fiber volume content from small (34/35% for 2D/1D), through medium (51%) to high (68%). Rectangular samples (45 × 4 × 2 mm) were cut from 1D plates along [0] and across [90] fibers. Similar size samples from 2D plates were cut along warp/weft axes as well as in two orthogonal bias directions. Selected side surfaces were polished for microscopic (SEM) observations. Short-beam-strength tests were performed in 3-point bending (l/h=4), with two AE sensors attached for damage monitoring, which allowed to interrupt loading sequence before final failure. The acoustic emission historic index was the most effective AE parameter in damage initiation control. Microcracks developing on polished composite side-surfaces were observed under the SEM and direct microscopic evidence confirmed fiber debonding to be the principal mechanism of crack initiation in these materials and testing conditions before any further damage.

Correlation of Acoustic Emission with Fractography in Bending of Glass–Epoxy Composites

“…Recently, studies on carbon fiber reinforced plastic (CFRP) composites have shown that the AE parameter named historic index (HI) may serve as an efficient experimental indicator of time of occurrence of fine damage initiation processes, including matrix micro-cracks and fiber debonding [17]. The HI indications registered during both monotonic and step-load bending tests of CFRP, also correlated well with clear scanning electron microscope (SEM) evidence showing such micro-defects [18].…”

Fatigue behavior of 3-D orthogonal woven composite with silane modification

“…The author considered that the acoustic emission historic index is the most effective AE parameter in detecting damage initiation. The AE count and energy were used to determined damage mode of 3-D woven composite during fatigue process [11][12][13][14][15][16][17][18][19][20][21]. Based on above studies, we can conclude that the AE technology is an effective method of detection of composite damage.…”

“…AE technology was used to detect the defects and density of crack in carbon fiber reinforced concrete composite [18,19]. Baran et al [20] detected the micro-crack initiation in carbon fiber reinforced polymer composites which subjected to shear stresses with acoustic emission (AE). The author considered that the acoustic emission historic index is the most effective AE parameter in detecting damage initiation.…”

Sounds and acoustic emission-based early fault diagnosis of induction motor: A review study

“…Nowadays, AE 136 becomes a very accurate and efficient method for fault, leaks and fatigue detection and monitoring techniques in materials 137,138 and structural analysis. 139 That include, concrete, 140,141 plastics, 142–144 polymers, 145–147 ceramics, 148–150 pipelines, 151–153 pressure vessels, 154,155 storage tanks, 156–159 bridges, 160–162 aircraft, 163,164 bucket trucks, 165 wood, 166–168 fiberglass, 169–172 composites, 173–175 welding, 176–178 , tubes, 179 aerospace structures 180–182 and finally for military applications. 183–185 Figure 2 illustrates AE instrumentation chain.…”