Hygrothermal effects on the translaminar fracture toughness of a highly toughened aerospace CFRP: Experimental characterisation and model prediction

Sengodan, Ganapathi A; Li, Shangkai; Allegri, Giuliano; Hallett, Stephen R

Abstract

The translaminar fracture toughness of wet (fully saturated) and dry (as manufactured) IM7/8552 laminates was measured using compact tension tests. Cross-ply ([90/0]8S) and quasi-isotropic ([90/45/0/-45]4S) laminates were tested at three different temperatures, namely 23 °C, 40 °C and 90 °C. The translaminar fracture toughness decreases non-linearly with the temperature for the dry laminates. However, for the wet laminates, the translaminar fracture toughness increases. The room-temperature tested wet cross-ply laminates exhibited a lower fracture toughness than the dry laminates. However, the initiation fracture toughness of the wet quasi-isotropic laminates is higher than for the dry laminates at all the test temperatures. The fractographic analysis of the failed specimens revealed that the hot-wet conditions promote additional fibre pull-out, which increases the fracture energy. The degradation of the epoxy matrix in the wet multi-directional laminates affected the progressive failure mechanism, and either increased or decreased the overall fracture energy depending on the lay-up sequence. For example, the initiation fracture toughness of the elevated temperature (90 °C) in wet quasi-isotropic specimens is ~17% higher than the room temperature (23 °C) dry laminates.

• Presentation Conference Type: Conference Paper (published)
• Acceptance Date: Jul 26, 2021
• Online Publication Date: Aug 3, 2021
• Publication Date: Aug 18, 2021
• Deposit Date: Sep 8, 2023
• Print ISSN: 1359-835X
• Publisher: Elsevier
• Volume: 150
• DOI: https://doi.org/10.5075/978-X-XXX-XXXXX-X
• Keywords: Translaminar; composites; fracture toughness; hygro-thermal; fibre pull-out