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Damage under progressive load–unload until failure was assessed for a new woven carbon fibre/flax fibre/epoxy hybrid composite via stiffness degradation D, permanent strain [Formula: see text], and crack density [Formula: see text]. Type A configuration had woven carbon fibres and unidirectional flax fibres (i.e. [0–90C2/0F12/0–90C2]), while Type B configuration had woven carbon fibres and ±45 ° obliquely angled flax fibres (i.e. [0–90C2/(±45)F6S/0–90C2]. Results were obtained for D in tension (Type A, 0.080; Type B, 0.089) and compression (Type A, 0.178; Type B, 0.207), [Formula: see text] in tension (Type A, 0.085%; Type B, 0.075%) and compression (Type A, 0.086%; Type B, 0.086%), and [Formula: see text] in tension (Type A, range = 0.12–1.06%; Type B, range = 0.6–1.43%) and compression (Type A, range = 0.65–1.20%; Type B, range = 1.05–2.20%). Failure involved flax fibre bundle cracks and interfacial cracks in the flax fibre/epoxy region.

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This is the first study, to the authors' knowledge, to simultaneously perform a direct comparison of finite element analysis, strain gage measurements, and infrared thermography for stress analysis under both static and dynamics tensile loads of the classic geometry of a composite plate with a center hole. The plate was made from a carbon fiber-reinforced epoxy composite with dimensions of 250 mm length × 25 mm width × 2.2 mm thickness and a 5 mm diameter center hole. Using static tensile loads of 1000 N, 2000 N, and 3000 N, the plate Von Mises stress field was evaluated using strain gages versus finite element analysis. Using cyclic tensile loads of 1000 N and 1600 N at 5 Hz, the plate Von Mises stress field was assessed using strain gages versus infrared thermography. The strain gages versus finite element analysis line-of-best-fit showed poor agreement (slope = 2.1, R = 0.81), although the slope could easily be applied as a correction factor when comparing the two methods. The strain gages versus infrared thermography showed much better agreement (slope = 0.95, R = 0.91). Finite element analysis displayed a “butterfly” stress field around the hole with peaks of 73.5 MPa (at 1000 N), 147 MPa (at 2000 N), and 220.5 MPa (at 3000 N). Infrared thermography showed a “ring” of high stress around the hole with peaks of 74.8 MPa (at 1000 N) and 102.9 MPa (at 1600 N). All three methods showed similar relative trends for the carbon fiber-reinforced epoxy plate.