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About the talk

Fibre-reinforced composites, and certainly carbon fibre composites (CFRP’s), are champions in combining stiffness, strength and low weight. One of the major limitations to the use of composites in primary structures is their rather limited toughness. The term “toughness” can be understood in different ways: (1) a low stress or strain threshold for damage initiation and ultimately to final failure, or (2) impact resistance, defined as resistance to damage development during, compression strength after impact, or the resistance against penetration by an impacting object. Two approaches have been followed in the toughness-related research at KU Leuven: either toughening carbon fibre composites, while sticking as close as possible to the initial CFRP stiffness and strength, or stiffening self-reinforced composites by hybridising them with carbon fibres, while keeping the toughness of SRC as its initially very high level.

In this lecture, focus will be on the latter approach. First, the initial research on hybridising SRPP by Yentl Swolfs will be briefly summarised. In this research, both UD and woven carbon fibre composites have been used as hybridising materials, and interesting combinations of increased stiffness and high toughness have been achieved. Then, some very recent results will be presented, in which random carbon fibre mats have been used as stiffening component. Whereas a random CF-mat /PP composite with about 16 vol% fibres behaves brittle, a hybrid with SRPP can keep SRPP’s initial toughness, even when hybridised with up to 8% of carbon fibres, resulting in a drastic increase in stiffness (almost x3) compared to SRPP. The controlling failure mechanisms will be discussed and guidelines for achieving the unusual combinations of stiffness and toughness will be presented.