Repair of impact damaged composites

Residual strength of composites with multiple impact damage

“…Unrepaired specimens were tested individually while repaired specimens were tested backto-back [19]. Four strain gauges were bonded on the unrepaired specimen; two above and two below the damage.…”

“…As previously mentioned, for multiple damage sites, this type of repair often results in the structure being classed as irreparable as the region of scarf extends into the irreparable zones. An alternative approach is to increase the strength by reducing the net sectional stresses [19]. This can be achieved by placing an external patch over the damaged area.…”

“…This can be achieved by placing an external patch over the damaged area. For this approach, the simple design methodology presented in [19] is extended to include multiple damage sites and substantiated via a laboratory test program. This methodology was further illustrated by a repair to two damaged horizontal stabilators, which were tested to design limit load [20].…”

Effects of geometric nonlinearities on damage propagation in patched beam-plates subjected to pressure loading

“…It is found that debonding behavior is dependent on the combination of several factors, including initial flaw size and geometry, support conditions, and physical and geometrical properties of the plates including shape of the structures and taper angle of the patch. Related studies [see, for example, Tarn and Shek (1991), Park et al (1992), Paul and Jones (1992) and Chue et al (1994)] pertain to load transfer to a repair patch from a plate with a (thickness) crack. Similar work falls specifically into the realm of bonded repair of damaged structures, such as that of Jones et al (1983), where a finite element method is developed to assess the behavior of flawed composite sheets (sheets possessing a crack or hole) with a bonded patch.…”

The Effects of Patch Properties on the Debonding Behavior of Patched Beam-Plates

“…This type of structures can be found in a range of applications, for example, as repair-patches on aircraft structures where the patches are used to prevent existing cracks from growing. In this case, it is of course of primary interest to establish if a patch will prevent a crack from growing, and studies have indicated that adhering a patch over a crack is indeed a very efficient way of preventing further crack growth (for example Baker [1], Chiu et al [2], Chue et al [3], Park et al [4], Paul and Jones [5], Rodrick [6], Sih and Hong [7], and Tarn and Shek [8]). However, it is also of significance to determine the integrity of the structure: the patch may not, for obvious reasons, be allowed to disintegrate from the base structure.…”