Bend-After-Impact Behaviors Of Stitched And Inter Laminar/Intra Laminar Hybrid Composites

Classic laminates can be easily delaminated under external force due to no reinforcement through thickness and low inter laminar performance. Stitching which sews the 2D textiles through thickness into quasi-3D textiles can compensate for that deficiency. Moreover, hybrid is another method enhancing inter laminar performance by different structures and different materials. This paper aims at improving the inter laminar and anti-impact performance of laminates.The experiments adopt T300 carbon-fiber woven fabrics, T300 carbon-fiber unidirectional fabrics, E-glass-fiber woven fabrics and carbon-fiber/glass-fiber 1:1 hybrid woven fabrics to conduct inter/intra laminar hybrid. Performs are stacked by 16 fiber fabric layers. There are five structures as four hybrid structures and one stitched structure. Carbon-fiber woven fabrics hybrid carbon-fiber unidirectional fabrics by inter laminar stacking CwCu, Carbon-fiber woven fabrics hybrid glass-fiber woven fabrics by inter laminar stacking CwGw, carbon-fiber/ glass-fiber woven fabrics stacking CGw, carbon-fiber/glass-fiber woven fabrics by carbon-fiber unidirectional fabrics by inter-laminar stacking CGwCu are the four hybrid structures. These structures are moulded by vacuum assisted RTM using JC02A mixtured epoxy resin. Low velocity impacts are conducted to these laminates with no damages on the surface of the specimens. CGwCu specimen is stitched because of its large displacement during impact. Stitched specimen CGwCuS and intra-laminar hybrid specimen CGw could sustain 3J energy impact as other composites can sustain 4J energy impact with no damages on the surface.Impact effects to the performance are studied by bend-after-impact behaviors and section damages.It is found that bend modulus after impact is more sensitive than bend strength after impact to impact damages. The bend modulus after impact decline about 15% for two inter laminar hybrid structures CWGW and CWCU.The bend modulus after impact decline about 30% for intra laminar hybrid structure CGW.The bend modulus after impact decline about 16% for inter+ intra laminar hybrid structure CGWCU.The bend modulus after impact decline about 11% for stitched structure CGwCuS. Then, the section are observed after cut. There are a small mount damages for two inter laminar hybrid structures CwGw and CWCU.Delaminations and cracks are existed in inter laminar hybrid and inter+intra laminar hybrid structures. Stitched structure CGWCU has few damages in internal due to the constraint of stitch thread.The experiments demonstrate that inter laminar hybrid composites possess a high inter laminar, anti-impact performance and damage tolerance. In addition, stitched composites have a low anti-impact performance while a strong performance for bend-after-impact. There is a better inter laminar performance and damage tolerance for stitched composites.