An experimental study on low velocity impact behavior of thermoplastic composites repaired by composite patches

Abstract

In this study, low velocity impact behavior of E-glass fiber-reinforced thermoplastic composites repaired by pressing external laminated composite patches was investigated by experimental methods. Thermoplastic composites were manufactured from polypropylene granules with two different fiber contents of 40 wt. % and 60 wt. %. Repaired specimens were prepared by using unidirectional E-glass reinforced polypropylene based thermoplastic prepregs. In order to compare the low velocity impact behavior of the repaired and unrepaired specimens, a number of single impact tests (ranging from energy levels of 10 J to 50 J) were carried out through a drop weight impact test machine with a hemispherical impactor. Low-velocity impact response of the specimens was investigated with cross-examining contact force-deformation curves and damaged specimens. Impact damages occurred in the upside and bottom surfaces of the composites were recorded from the visual inspection and compared for repaired and unrepaired specimens. According to experimental results, bending stiffness and maximum contact force of the specimens having fiber content of 60 wt.% are higher than those of 40 wt.%. Moreover, it was concluded that the patch repaired specimens have achieved a better performance in terms of maximum contact force and absorbed energy compared to the intact specimens.

A case study on the performance of repaired sandwich composite aeronautical structures in different failure characteristics under bending loading

“…It is a desired result in sandwich repair process that the honeycomb core mass can be in the optimum range of 50%-66.7% of the whole sandwich panel mass. 7 Studies about repair procedures on fibre reinforced polymer composite laminated beams or panels and their mechanical and damage analysis under various loadings such as bending, buckling, impact [8][9][10][11][12][13][14][15][16] and even fatigue 17 are worthy and similar with sandwich repair to a certain extent. Since the sandwich material is not in the form of a conventional laminated composite structure and if the sandwich core is also damaged and needs repair, these studies about laminated composite structures should be evaluated in a different category.…”

Reconsolidation effect on impact, compression after impact and thermal properties of poly (aryl ether ketone) composites for aeronautical applications

“…[19][20][21] Compression after impact (CAI) is a method normally used to evaluate the structural health allowing to measure the residual compression strength of a specimen submitted to the LVI. [22][23][24] These tests occur in two steps: first, a transverse low-velocity impact is applied to a specimen which will be capable of producing internal damage and, subsequently, the in-plane compression of this impacted laminate is evaluated to determine its residual strength. 25 Compressive strength reduces after an impact, so when the compression mechanisms interact with an induced impact the damage propagates generating the failure at significantly low load levels when compared to a laminate without impact damage.…”

Effect of patch thickness and size on the low-velocity impact of patch-repaired CFRP composite laminates for rail vehicles

“…Considering the low-velocity impacts that repaired laminates may experience, researchers have conducted many related studies. The low-velocity impact response study of patch-repaired composite laminates involved different impact conditions (including different energy levels [13], multiple repeated impacts [14,15], and different impact locations [16,17]) and properties of adhesive and patch [18,19]. The configuration of the patch is an important factor affecting low-velocity impact performance.…”

“…Researchers have conducted extensive research into the mechanical performance of patchrepaired laminates [10][11][12][13][14][15][16][17][18][19]. Campilho et al [10] established single and double-lap repair models of carbon-epoxy composite and studied the effects of material properties, overlap length, patch thickness, stacking order, etc.…”